Posts Tagged ‘REST

23
Apr
11

Nested JSON

This page describes the process of performing CRUD operations on Java Beans that have Nested Properties using ExtJS.

Requirements

The Item bean contains a length, width, and height property. We will move those attributes to a new bean called Dimension and add a dimension attribute to the Item class.

This will result in the editor Grid submitting the following xml in the Request Body:

<?xml version="1.0" encoding="UTF-8"?>
	<item>
		<itemId>5</itemId>
		<name>tes</name>
		<description>111111</description>
		<stockQty>2</stockQty>
		<color>blue</color>
		<dimension.length>1</dimension.length>
		<dimension.width>1</dimension.width>
		<dimension.height>1</dimension.height>
	</item>

The following changes need to be done:

  1. Create a new Dimension class, modify the Item class to use it.
  2. Modify the IBATIS sql map xml files
  3. Modify ExtJS JsonReader to read the nested information

src/main/java/com/test/Dimension.java

package com.test;

import java.math.BigDecimal;

public class Dimension {
    private BigDecimal length;
    private BigDecimal width;
    private BigDecimal height;
    
    
	public BigDecimal getLength() {
		return length;
	}
	public void setLength(BigDecimal length) {
		this.length = length;
	}
	public BigDecimal getWidth() {
		return width;
	}
	public void setWidth(BigDecimal width) {
		this.width = width;
	}
	public BigDecimal getHeight() {
		return height;
	}
	public void setHeight(BigDecimal height) {
		this.height = height;
	}
}

Item

Replace the implementation of Item.java with the following.

src/main/java/com/test/Item.java

package com.test;
 
import java.math.BigDecimal;
import javax.xml.bind.annotation.XmlRootElement;
 
/**
 * Represents an item in inventory or in a shopping cart.
 */
@XmlRootElement
public class Item {
    private Integer itemId;
    private String oemId;
    private String name;
    private String description;
    private String imageURL;
    private String color;
    private BigDecimal price;
    private Dimension dimension = new Dimension();
     
    /**
     * Weight in grams
     */
    private BigDecimal weight;
    /**
     * Quantity in stock.
     */
    private Integer stockQty;
 
    public Item() {
        super();
    }
 
    public Item(Integer id, String name) {
        this.name = name;
        this.itemId = id;
    }
 
    public Integer getItemId() {
        return itemId;
    }
    public void setItemId(Integer itemId) {
        this.itemId = itemId;
    }
    public String getOemId() {
        return oemId;
    }
    public void setOemId(String oemId) {
        this.oemId = oemId;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }
    public String getColor() {
        return color;
    }
    public void setColor(String color) {
        this.color = color;
    }
    public String getImageURL() {
        return imageURL;
    }
    public void setImageURL(String imageURL) {
        this.imageURL = imageURL;
    }
    public BigDecimal getPrice() {
        return price;
    }
    public void setPrice(BigDecimal price) {
        this.price = price;
    }

    public BigDecimal getWeight() {
        return weight;
    }
    public void setWeight(BigDecimal weight) {
        this.weight = weight;
    }
 
    public Integer getStockQty() {
        return stockQty;
    }
 
    public void setStockQty(Integer stockQty) {
        this.stockQty = stockQty;
    }

    public void setDimension(Dimension dimension) {
		this.dimension = dimension;
    }

    public Dimension getDimension() {
		return dimension;
    }
}

IBATIS SQL Mapper

Change the SQL mapper configuration file to look like this…

src/main/resources/com/test/ItemDataManager.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE sqlMap
        PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"
        "http://ibatis.apache.org/dtd/sql-map-2.dtd">
<sqlMap namespace="Item">
 
<typeAlias alias="Item" type="com.test.Item" />

    <resultMap id="itemResultMap" class="Item">
		<result property="itemId" column="itemId"/>
		<result property="oemId" column="oemId"/>
		<result property="name" column="name"/>
		<result property="description" column="description"/>
		<result property="color" column="color"/>
		<result property="imageURL" column="imageURL"/>
		<result property="price" column="price"/>
		<result property="dimension.length" column="length"/>
		<result property="dimension.width" column="width"/>
		<result property="dimension.height" column="height"/>
		<result property="weight" column="weight"/>
		<result property="stockQty" column="stockQty"/>
    </resultMap>

 
    <select id="allItems" resultMap="itemResultMap" >
        select item_id as itemId,
        oem_id as oemId,
        item_x as name,
        description as description,
        color as color,
        image_url as imageURL,
        price as price,
        length as length,
        width as width,
        height as height,
        weight as weight,
        stock_qty as stockQty
        from item;
    </select>
    <select id="getItemInfo" parameterClass="int" resultMap="itemResultMap" >
        select item_id as itemId,
        oem_id as oemId,
        item_x as name,
        description as description,
        color as color,
        image_url as imageURL,
        price as price,
        length as length,
        width as width,
        height as height,
        weight as weight,
        stock_qty as stockQty
        from item where item_id = #id#;
    </select>
 
    <insert id="itemInsert" parameterClass="Item">
        insert into item (oem_id,
            item_x,
            description,
            color,
            image_url,
            price,
            length,
            width,
            height,
            weight,
            stock_qty)
        values ( #oemId#, #name#, #description#, #color#,
            #imageURL#, #price#, #dimension.length#, #dimension.width#,
            #dimension.height#, #weight#, #stockQty# );
        <selectKey resultClass="int" >
            <!-- HSQLDB -->
            CALL IDENTITY();
            <!-- MySQL -->
            <!-- SELECT LAST_INSERT_ID(); -->
        </selectKey>
    </insert>
    <update id="updateItem" parameterClass="Item">
        update item set oem_id = #oemId#, item_x = #name#, description=#description#,
            color = #color#, image_url = #imageURL#, price = #price#, length = #dimension.length#,
            width = #dimension.width#, height = #dimension.height#, weight = #weight#, stock_qty = #stockQty#
        where item_id = #itemId#;
    </update>
    <delete id="deleteItem" parameterClass="java.lang.Integer">
        delete from item where item_id = #itemId#;
    </delete>
</sqlMap>

Change the Grid

MyApp={};
MyApp.getContext = function() {
	var base = document.getElementsByTagName('base')[0];
	if (base && base.href && (base.href.length > 0)) {
		base = base.href;
	} else {
		base = document.URL;
	}
	return base.substr(0, base.indexOf("/", base.indexOf("/", base.indexOf("//") + 2) + 1));
};

var App = new Ext.App({});
 
var proxy = new Ext.data.HttpProxy({
	url: MyApp.getContext() + '/appdata/itemresource'
});

var reader = new Ext.data.JsonReader({
    totalProperty: 'total',
    successProperty: 'success',
    idProperty: 'itemId',
    root: 'data',
    record: 'item',
    messageProperty: 'message',  // <-- New "messageProperty" meta-data
    fields : [
              {name: 'itemId'},
              {name: 'name', allowBlank: false},
              {name: 'description', allowBlank: true},
              {name: 'stockQty', allowBlank: true},
              {name: 'color', allowBlank: true},
// The 'mapping' field allows binding to complex nested JSON objects              
              {name: 'length', allowBlank: true, mapping: 'dimension.length'},              
              {name: 'width', allowBlank: true, mapping: 'dimension.width'},              
              {name: 'height', allowBlank: true, mapping: 'dimension.height'}              
    ]
});

// The new DataWriter component.
var writer = new Ext.data.XmlWriter({
    encode : false,
    writeAllFields : true,
    xmlEncoding : "UTF-8"
});

// Typical Store collecting the Proxy, Reader and Writer together.
var store = new Ext.data.Store({
    id: 'item',
    restful: true,     // <-- This Store is RESTful
    proxy: proxy,
    reader: reader,
    writer: writer    // <-- plug a DataWriter into the store
});

// load the store
store.load();

// The following is necessary to map the Record Fields to the grid columns.
var userColumns =  [
    {header: "Item Id", width: 40, sortable: true, dataIndex: 'itemId'},
    {header: "Item Name", width: 100, sortable: true, dataIndex: 'name', editor: new Ext.form.TextField({})},
    {header: "Description", width: 100, sortable: true, dataIndex: 'description', editor: new Ext.form.TextField({})},
    {header: "Quantity", width: 100, sortable: true, dataIndex: 'stockQty', editor: new Ext.form.TextField({})},
    {header: "Color", width: 100, sortable: true, dataIndex: 'color', editor: new Ext.form.TextField({})},
    {header: "Length", width: 100, sortable: true, 
    	dataIndex: 'length', editor: new Ext.form.TextField({})},
    {header: "Width", width: 100, sortable: true, 
    	dataIndex: 'width', editor: new Ext.form.TextField({})},
    {header: "Height", width: 100, sortable: true, 
    	dataIndex: 'height', editor: new Ext.form.TextField({})}
];

Ext.onReady(function() {
    Ext.QuickTips.init();

    // use RowEditor for editing
    var editor = new Ext.ux.grid.RowEditor({
        saveText: 'Save'
    });

    // Create a typical GridPanel with RowEditor plugin
    var userGrid = new Ext.grid.GridPanel({
        renderTo: 'user-grid',
        iconCls: 'icon-grid',
        frame: true,
        title: 'Fun with RESTful CRUD',
        height: 300,
        store: store,
        plugins: [editor],
        columns : userColumns,
    	enableColumnHide: false,
        tbar: [{
        	id: 'addBtn',
            text: 'Add',
            iconCls: 'silk-add',
            handler: onAdd
        }, '-', {
        	id: 'deleteBtn',
            text: 'Delete',
            iconCls: 'silk-delete',
            handler: onDelete
        }, '-'],
        viewConfig: {
            forceFit: true
        }
    });

    function onAdd(btn, ev) {
        var u = new userGrid.store.recordType({
            first : '',
            last: '',
            email : ''
        });
        editor.stopEditing();
        userGrid.store.insert(0, u);
        editor.startEditing(0);
    }

    // Disable the buttons when editing.
    editor.addListener('beforeedit', function(roweditor, rowIndex){
        Ext.getCmp('addBtn').disable();
        Ext.getCmp('deleteBtn').disable();
    });
    editor.addListener('afteredit', function(roweditor, rowIndex){
        Ext.getCmp('addBtn').enable();
        Ext.getCmp('deleteBtn').enable();
    });
    editor.addListener('canceledit', function(roweditor, rowIndex){
    	// get fresh records from the database.
        userGrid.store.reload({});
        Ext.getCmp('addBtn').enable();
        Ext.getCmp('deleteBtn').enable();
    });     

    function onDelete() {
        var rec = userGrid.getSelectionModel().getSelected();
        if (!rec) {
            return false;
        }
        userGrid.store.remove(rec);
    }
    activateGridValidation(userGrid);
});

Test the application

In the project top folder type in the following command to compile and run the code in jetty servlet engine.

mvn clean compile jetty:run

Navigate to the following URL:
http://localhost:8080/crud/

Modify the application presented in Part II

In this section we will modify the application presented in part II of my posting in this series.

Regular form panel can submit nested bean information. The submission looks like this:

name=4&description=444444&stockQty=4&color=blue&dimension.length=4&dimension.width=4&dimension.height=4

Modify the form.html page to look like this…

src/main/webapp/form.html

<html>
<head>
 
<link rel="stylesheet" type="text/css"
    href="http://dev.sencha.com/deploy/ext-3.3.1/resources/css/ext-all.css"/>
 
<script type="text/javascript"
    src="http://dev.sencha.com/deploy/ext-3.3.1/adapter/ext/ext-base-debug.js">
</script>
<script type="text/javascript"
    src="http://dev.sencha.com/deploy/ext-3.3.1/ext-all-debug.js">
</script>
 
<script type="text/javascript">
 
MyApp={};
MyApp.getContext = function() {
    var base = document.getElementsByTagName('base')[0];
    if (base && base.href && (base.href.length > 0)) {
        base = base.href;
    } else {
        base = document.URL;
    }
    return base.substr(0, base.indexOf("/", base.indexOf("/", base.indexOf("//") + 2) + 1));
};
 
function buildWindow() {
    Ext.QuickTips.init();
    Ext.form.Field.prototype.msgTarget = 'side';
    var bd = Ext.getBody();
 
    var fs = new Ext.FormPanel({
        labelWidth: 75,
        frame: true,
        title:'Form with crazy amount of validation',
        bodyStyle:'padding:5px 5px 0',
        defaults: {width: 230},
        waitMsgTarget: true,
        defaultType: 'textfield',    
 
        items: [{
                fieldLabel: 'Item Name',
                name: 'name'
            },{
                fieldLabel: 'Description',
                name: 'description'
            },{
                fieldLabel: 'Quantity',
                name: 'stockQty'
            }, {
                fieldLabel: 'Color',
                name: 'color'
            }, {
                fieldLabel: 'Length',
                name: 'dimension.length'
		    }, {
		        fieldLabel: 'Width',
		        name: 'dimension.width'
			}, {
			    fieldLabel: 'Height',
			    name: 'dimension.height'
			}
        ],    
 
    });
 
    var onSuccessOrFail = function(form, action) {
        var result = action.result;
 
        if(result.success) {
            Ext.MessageBox.alert('Success', 'Success!');
            userGrid.store.reload({});
        } else { // put code here to handle form validation failure.
        }
 
    }
 
    var submit = fs.addButton({
        text: 'Submit',
        disabled:false,
        handler: function(){
            fs.getForm().submit({
                url:MyApp.getContext() +'/app/itemresource',
                waitMsg:'Submitting Data...',
                submitEmptyText: false,
                success : onSuccessOrFail,
                failure : onSuccessOrFail
            });
        }
    });
 
    fs.render('form-first');
 
    // the following is necessary to display the grid.
 
// The following is necessary to map the Record Fields to the grid columns.
var userColumns =  [
    {header: "Item Id", width: 40, sortable: true, dataIndex: 'itemId'},
    {header: "Item Name", width: 100, sortable: true, dataIndex: 'name', editor: new Ext.form.TextField({})},
    {header: "Description", width: 100, sortable: true, dataIndex: 'description', editor: new Ext.form.TextField({})},
    {header: "Quantity", width: 100, sortable: true, dataIndex: 'stockQty', editor: new Ext.form.TextField({})},
    {header: "Color", width: 100, sortable: true, dataIndex: 'color', editor: new Ext.form.TextField({})},
    {header: "Length", width: 100, sortable: true, 
    	dataIndex: 'length', editor: new Ext.form.TextField({})},
    {header: "Width", width: 100, sortable: true, 
    	dataIndex: 'width', editor: new Ext.form.TextField({})},
    {header: "Height", width: 100, sortable: true, 
    	dataIndex: 'height', editor: new Ext.form.TextField({})}
];
 
    var proxy = new Ext.data.HttpProxy({
        url: MyApp.getContext() + '/app/itemresource'
    });
 
    var reader = new Ext.data.JsonReader({
        totalProperty: 'total',
        successProperty: 'success',
        idProperty: 'itemId',
        root: 'data',
        record: 'item',
        messageProperty: 'message',  // <-- New "messageProperty" meta-data
        fields : [
                  {name: 'itemId'},
                  {name: 'name', allowBlank: false},
                  {name: 'description', allowBlank: true},
                  {name: 'stockQty', allowBlank: true},
              {name: 'color', allowBlank: true},
// The 'mapping' field allows binding to complex nested JSON objects              
              {name: 'length', allowBlank: true, mapping: 'dimension.length'},              
              {name: 'width', allowBlank: true, mapping: 'dimension.width'},              
              {name: 'height', allowBlank: true, mapping: 'dimension.height'}              
        ]
    });
 
    // Typical Store collecting the Proxy, Reader and Writer together.
    var store = new Ext.data.Store({
        id: 'item',
        restful: true,     // <-- This Store is RESTful
        proxy: proxy,
        reader: reader
    });
 // load the store
    store.load();
 
    // Create a typical GridPanel with RowEditor plugin
    var userGrid = new Ext.grid.GridPanel({
        renderTo: 'user-grid',
        iconCls: 'icon-grid',
        frame: true,
        title: 'Records in HyperSQL Database',
        height: 300,
        store: store,
        columns : userColumns,
        enableColumnHide: false,
        viewConfig: {
            forceFit: true
        }
    });
 
}
Ext.onReady(buildWindow);
</script>
</head>
<body>
 
<div class="container" style="width:500px">
    <div id="form-first"></div>
    <div id="user-grid"></div>
</div>
 
</body>
</html>
23
Apr
11

CRUD with Extjs

The content of this page has moved/combined with another page: https://numberformat.wordpress.com/2011/04/07/restful-crud-using-extjs/

07
Apr
11

RESTful CRUD using extJS

This page describes how to create an extJS based web application that performs RESTful CRUD operations on resources in a Java JEE web application. For those that want instant gratification, a complete working version of the project is available at the following SVN location. http://ext-jsf.googlecode.com/svn/trunk/wordpress/2011/04/restful-crud-using-extjs/. Get the project and skip to the Test The Application section of this page.

Background

Each Entity object (resource) suppose to have a unique URL in a REST based application. This design consideration makes it easy for JavaScript frameworks like extJS to perform CRUD operations on the resource based on user’s actions.

This tutorial builds from an article about ExtJS + Spring MVC validation using commons-validator. While that page only allowed you to create new items by issuing a HTTP POST, this page will complete the CRUD concept allowing the browser to issue GET, PUT, and DELETE methods to manage items in the database.

CRUD is composed of the following parts:

Create(aka. HTTP POST)

The extJS component issues a HTTP POST to the URL listed in the data store. HTTP POST is neither safe or omnipotent. This means that the HTTP POST can change the state of the object and also multiple invocations can be disruptive (it will create an extra object if called twice by mistake). The component is expecting a JSON “success” string and a representation of the object at a minimum. The id of the item is not passed in the URL because it is not known yet.

Read (aka. HTTP GET)

The extJS component is expecting a list of objects to be returned when it issues a GET to the URL. The list of items are displayed on the grid based on the configuration of the reader or metaData. HTTP GET is a “safe” operation. This means that calls to a resource using GET will not change the state of the resource. The component is expecting a JSON “success” string at a minimum.

Update (aka. HTTP PUT)

The extJS component sends the id in the URL path and the representation of the modified object in the body of the PUT. HTTP PUT is not “safe” however it is “omnipotent”. This means that an HTTP PUT can change the state of the object however multiple submissions of this PUT will not will not be disruptive. The component is expecting a JSON “success” and a representation of the object at a minimum.

Destroy (aka. HTTP DELETE)

The extJS component sends the id in the URL path. HTTP DELETE is not safe however it is omnipotent. This means that DELETE operations will change the state of the object on the server side however multiple invocations of this will not be disruptive. (since deleting the same id the second time will not do anything). The component is expecting a JSON “success” string at a minimum.

This page describes all you need to create and configure a self-contained java application that interacts with an in-memory Java database.

Requirements

Procedure

Verify The Existing Project

Open up a console with to the project’s base directory.

Convert XML to POJO

The Grid on this page uses a XmlWriter to submit the Item as XML in the Request Body. In order to convert the XML into a JavaBean we will be using JAXB.

Converting XML to JavaBeans using JAXB was covered on the following page “using jaxb to convert between xml and pojo“.

Modify Item.java and define “@XmlRootElement” right above the class name and add the extra import statement.

src/main/java/com/test/Item.java

...
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Item {
...

The following class is used by JAXB to create an instance of an Item Bean.

src/main/java/com/test/ObjectFactory.java

package com.test;

import javax.xml.bind.annotation.XmlRegistry;

@XmlRegistry
public class ObjectFactory {
 
    public ObjectFactory() {
    }
 
    public Item createItem() {
        return new Item();
    }
}

Binding the Bean from the Request Body

The request body contains XML representation of beans. Spring MVC 2.5 has a @ModelAttribute annotation that does this for us. However the default implementation expects the input as HTTP form attributes. For example (“itemId=1&name=testName&description=TestDescription”). Since the Grid will be posting the Bean as XML we need to override a few classes.

The following 4 classes need to be created:

  1. CustomAnnotationMethodHandlerAdapter.java
  2. XMLServletRequestDataBinder.java
  3. ServletRequestBodyXMLPropertyValues.java
  4. XMLWebUtils.java

src/main/java/com/test/fw/CustomAnnotationMethodHandlerAdapter.java

package com.test.fw;

import javax.servlet.http.HttpServletRequest;

import org.springframework.web.bind.ServletRequestDataBinder;
import org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter;

/**
 * The whole purpose of this class it to allow it to specify XMLServletRequestDataBinder
 * instead of the ServletRequestDataBinder as defined in the parent class.
 */
public class CustomAnnotationMethodHandlerAdapter extends AnnotationMethodHandlerAdapter {
	@Override
	protected ServletRequestDataBinder createBinder(HttpServletRequest request,
			Object target, String objectName) throws Exception {		
		return new XMLServletRequestDataBinder(target, objectName);
	}
}

src/main/java/com/test/fw/XMLServletRequestDataBinder.java

package com.test.fw;

import javax.servlet.ServletRequest;

import org.springframework.beans.MutablePropertyValues;
import org.springframework.web.bind.ServletRequestDataBinder;
import org.springframework.web.multipart.MultipartHttpServletRequest;

/**
 * The purpose of this class it call ServletRequestBodyXMLPropertyValues instead
 * of ServletRequestPropertyValues in the bind method.
 */
public class XMLServletRequestDataBinder extends ServletRequestDataBinder {

	public XMLServletRequestDataBinder(Object target, String objectName) {
		super(target, objectName);
	}

	@Override
	public void bind(ServletRequest request) {
		MutablePropertyValues mpvs = new ServletRequestBodyXMLPropertyValues(request);
		if (request instanceof MultipartHttpServletRequest) {
			MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
			bindMultipartFiles(multipartRequest.getFileMap(), mpvs);
		}
		doBind(mpvs);
	}

}

src/main/java/com/test/fw/ServletRequestBodyXMLPropertyValues.java

package com.test.fw;

import javax.servlet.ServletRequest;

import org.springframework.beans.MutablePropertyValues;


/**
 * PropertyValues implementation created from XML in the ServletRequest body. This 
 * implementation uses the XMLWebUtils instead of WebUtils to extract property values
 * from the ServletRequest body.
 */
public class ServletRequestBodyXMLPropertyValues extends MutablePropertyValues {
	private static final long serialVersionUID = 1L;

	public ServletRequestBodyXMLPropertyValues(ServletRequest request) {
		this(request, null, null);
	}
	
	public ServletRequestBodyXMLPropertyValues(ServletRequest request, String prefix, String prefixSeparator) {
		super(XMLWebUtils.getElementsStartingWith(
				request, (prefix != null) ? prefix + prefixSeparator : null));
	}

}

src/main/java/com/test/fw/XMLWebUtils.java

package com.test.fw;

import java.io.IOException;
import java.util.Map;
import java.util.TreeMap;

import javax.servlet.ServletRequest;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.springframework.util.Assert;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * This class offers some enhanced features relating to REST processing
 * XML submitted by extJS component as part of a form submission.
 */
public class XMLWebUtils {
	static class MyDefaultHandler extends DefaultHandler {
		private String tempVal;
		
		final private Map<String, String> params;
		private String rootElement;
		private String prefix;
		
		public MyDefaultHandler(Map<String, String> map, String prefix) {
			this.params = map;
			this.prefix = prefix;
		}
		
		@Override
		public void startElement(String uri, String localName, String qName,
				Attributes attributes) throws SAXException {
			if(qName == null) {
				return;
			}
			
			if(rootElement == null) {
				rootElement = qName;
			} 
			
		}
	    
		public void characters(char[] ch, int start, int length) throws SAXException {
	        tempVal = new String(ch,start,length);
	    }
	    
		@Override
		public void endElement(String uri, String localName, String qName)
				throws SAXException {

			if(qName.equalsIgnoreCase(rootElement)) {
				rootElement = null;
			} else {
				params.put(qName, tempVal);
				tempVal = null;
			}
		}
	}
	
	/**
	 * This method creates a map of element values submitted by the extJS component.
	 * The extjs component has been set to submit an xml representation of the data. 
	 * This method uses SAX API that is built into the JDK 1.5 and above.
	 * 
	 * @param request
	 * @param prefix
	 * @return
	 */
	public static Map<String, String> getElementsStartingWith(ServletRequest request, String prefix) {
		Assert.notNull(request, "Request must not be null");
		
		Map<String, String> params = new TreeMap<String, String>();

		if (prefix == null) {
			prefix = "";
		}
        //get a factory
        SAXParserFactory spf = SAXParserFactory.newInstance();
        try {
            SAXParser sp = spf.newSAXParser();
            sp.parse(request.getInputStream(), new MyDefaultHandler(params, prefix));
        }catch(SAXException se) {
            se.printStackTrace();
        }catch(ParserConfigurationException pce) {
            pce.printStackTrace();
        }catch (IOException ie) {
            ie.printStackTrace();
        }
		return params;
	}
}

Configure SpringMVC to use the Custom Annotation Method Handler Adapter

The AnnotationMethodHandlerAdapters is configured using the spring-servlet.xml file. You can only have one HandlerAdapter per URL mapping. We will configure an alternate HandlerAdapter using another mapping.

Modify the web.xml and add an additional DispatcherServlet.

src/main/webapp/WEB-INF/web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">
 
    <display-name>Archetype Created Web Application</display-name>
 
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
 
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
 
    <listener>
        <listener-class>com.test.DBLifecycleContextListener</listener-class>
    </listener>
 
    <servlet>
        <servlet-name>spring</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>springdata</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    </servlet>
 
    <servlet-mapping>
        <servlet-name>spring</servlet-name>
        <url-pattern>/app/*</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>springdata</servlet-name>
        <url-pattern>/appdata/*</url-pattern>
    </servlet-mapping>
 
</web-app>

The following is the configuration file for the new DispatcherServlet we defined above. Spring MVC follows a standard naming convention with reading xml configurations. If the servlet name is “springdata” then the springdata-servlet.xml file in the WEB-INF folder will be read. The below configuration file is similar to the original one except we have swapped out the HandlerAdapter for “com.test.CustomAnnotationMethodHandlerAdapter”.

src/main/webapp/WEB-INF/springdata-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
 
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
 
http://www.springframework.org/schema/context
 
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
 
    <context:annotation-config />
    <context:component-scan base-package="com.test" />
 
    <bean
        class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping" />
    <bean
        class="com.test.fw.CustomAnnotationMethodHandlerAdapter" />
 
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>
 
</beans>

Setup the ExtJS Front End JavaScript/HTML

Lastly we will set-up the extJS Front End.

The following enhances the extJS editor grid to display validation failures. Thanks to Oskar Johansson for providing a excellent solution.

src/main/webapp/gridValidation.js

// Oskar Johansson, http://onkelborg.com
    activateGridValidation = function (grid) {
        var store = grid.getStore();
        var mapRecordToRequestJsonData = [];
        var mapRecordToRequestRecord = [];
        var storeOnBeforeSave = function (store, data) {
            mapRecordToRequestJsonData = [];
            mapRecordToRequestRecord = [];
        };
        var storeOnBeforeWrite = function (dataProxy, action, rs, params) {
            mapRecordToRequestJsonData.push(params.jsonData);
            mapRecordToRequestRecord.push(rs);
        };
        var storeOnException = function (dataProxy, type, action, options, response, arg) {
            if (action == "create" || action == "update") {
                var erroneousObject = mapRecordToRequestRecord[mapRecordToRequestJsonData.indexOf(options.jsonData)];
                var rowIndex = store.indexOf(erroneousObject);
                var colModel = grid.getColumnModel();
                var gridView = grid.getView();
                var errorsInner;
                var errors = response.raw ? response.raw.errors : ((errorsInner = Ext.decode(response.responseText)) ? errorsInner.errors : null);
                var editableColumns = [];
                for (var i = 0; i < colModel.getColumnCount(); i++) {
                    var column = colModel.getColumnById(colModel.getColumnId(i));
                    if (column.getCellEditor(rowIndex)) {
                        editableColumns.push(colModel.getDataIndex(i));
                    }
                }
                if (errors) {
                    var erroneousColumns = [];
                    for (var x in errors) {
                        erroneousColumns.push(x);
                    }
                    for (var i = 0; i < erroneousColumns.length; i++) {
                        editableColumns.splice(editableColumns.indexOf(erroneousColumns[i]), 1);
                    }
                    for (var i = 0; i < erroneousColumns.length; i++) {
                        var errKey = erroneousColumns[i];
                        var colIndex = colModel.findColumnIndex(errKey);
                        var msg = errors[errKey];
                        var cell = gridView.getCell(rowIndex, colIndex);
                        var cellElement = Ext.get(cell);
                        var cellInnerElement = cellElement.first();
                        cellInnerElement.addClass("x-form-invalid");
                        cellInnerElement.set({ qtip: msg });
                    }
                }
                for (var i = 0; i < editableColumns.length; i++) {
                    var colIndex = colModel.findColumnIndex(editableColumns[i]);
                    var cell = gridView.getCell(rowIndex, colIndex);
                    var cellElement = Ext.get(cell);
                    var cellInnerElement = cellElement.first();
                    cellInnerElement.removeClass("x-form-invalid");
                    cellInnerElement.set({ qtip: "" });
                }
            }
        };
        store.proxy.on("exception", storeOnException);
        store.proxy.on("beforewrite", storeOnBeforeWrite);
        store.on("beforesave", storeOnBeforeSave);
        grid.on("destroy", function () {
            store.proxy.un("exception", storeOnException);
            store.proxy.un("beforewrite", storeOnBeforeWrite);
            store.un("beforesave", storeOnBeforeSave);
        });
    }; 

The next file contains the JavaScript code that sets up the editor grid panel.
src/main/webapp/restful.js

MyApp={};
MyApp.getContext = function() {
	var base = document.getElementsByTagName('base')[0];
	if (base && base.href && (base.href.length > 0)) {
		base = base.href;
	} else {
		base = document.URL;
	}
	return base.substr(0, base.indexOf("/", base.indexOf("/", base.indexOf("//") + 2) + 1));
};

var App = new Ext.App({});
 
var proxy = new Ext.data.HttpProxy({
	url: MyApp.getContext() + '/appdata/itemresource'
});

var reader = new Ext.data.JsonReader({
    totalProperty: 'total',
    successProperty: 'success',
    idProperty: 'itemId',
    root: 'data',
    record: 'item',
    messageProperty: 'message',  // <-- New "messageProperty" meta-data
    fields : [
              {name: 'itemId'},
              {name: 'name', allowBlank: false},
              {name: 'description', allowBlank: true},
              {name: 'stockQty', allowBlank: true},
              {name: 'color', allowBlank: true}
    ]
});

// The new DataWriter component.
var writer = new Ext.data.XmlWriter({
    encode : false,
    writeAllFields : true,
    xmlEncoding : "UTF-8"
});

// Typical Store collecting the Proxy, Reader and Writer together.
var store = new Ext.data.Store({
    id: 'item',
    restful: true,     // <-- This Store is RESTful
    proxy: proxy,
    reader: reader,
    writer: writer    // <-- plug a DataWriter into the store
});

// load the store
store.load();

// The following is necessary to map the Record Fields to the grid columns.
var userColumns =  [
    {header: "Item Id", width: 40, sortable: true, dataIndex: 'itemId'},
    {header: "Item Name", width: 100, sortable: true, dataIndex: 'name', editor: new Ext.form.TextField({})},
    {header: "Description", width: 100, sortable: true, dataIndex: 'description', editor: new Ext.form.TextField({})},
    {header: "Quantity", width: 100, sortable: true, dataIndex: 'stockQty', editor: new Ext.form.TextField({})},
    {header: "Color", width: 100, sortable: true, dataIndex: 'color', editor: new Ext.form.TextField({})}
];

Ext.onReady(function() {
    Ext.QuickTips.init();

    // use RowEditor for editing
    var editor = new Ext.ux.grid.RowEditor({
        saveText: 'Save'
    });

    // Create a typical GridPanel with RowEditor plugin
    var userGrid = new Ext.grid.GridPanel({
        renderTo: 'user-grid',
        iconCls: 'icon-grid',
        frame: true,
        title: 'Fun with RESTful CRUD',
        height: 300,
        store: store,
        plugins: [editor],
        columns : userColumns,
    	enableColumnHide: false,
        tbar: [{
        	id: 'addBtn',
            text: 'Add',
            iconCls: 'silk-add',
            handler: onAdd
        }, '-', {
        	id: 'deleteBtn',
            text: 'Delete',
            iconCls: 'silk-delete',
            handler: onDelete
        }, '-'],
        viewConfig: {
            forceFit: true
        }
    });

    function onAdd(btn, ev) {
        var u = new userGrid.store.recordType({
            first : '',
            last: '',
            email : ''
        });
        editor.stopEditing();
        userGrid.store.insert(0, u);
        editor.startEditing(0);
    }

    // Disable the buttons when editing.
    editor.addListener('beforeedit', function(roweditor, rowIndex){
        Ext.getCmp('addBtn').disable();
        Ext.getCmp('deleteBtn').disable();
    });
    editor.addListener('afteredit', function(roweditor, rowIndex){
        Ext.getCmp('addBtn').enable();
        Ext.getCmp('deleteBtn').enable();
    });
    editor.addListener('canceledit', function(roweditor, rowIndex){
    	// get fresh records from the database.
        userGrid.store.reload({});
        Ext.getCmp('addBtn').enable();
        Ext.getCmp('deleteBtn').enable();
    });     

    function onDelete() {
        var rec = userGrid.getSelectionModel().getSelected();
        if (!rec) {
            return false;
        }
        userGrid.store.remove(rec);
    }
    activateGridValidation(userGrid);
});

The following file pulls everything together.
src/main/webapp/grid.html

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>RESTful Store Example</title>

<!-- extJS JavaScript files -->
<script type="text/javascript"
    src="http://dev.sencha.com/deploy/ext-3.3.1/adapter/ext/ext-base-debug.js">
</script> 
<script type="text/javascript"
    src="http://dev.sencha.com/deploy/ext-3.3.1/ext-all-debug.js">
</script>
<!-- extJS example JavaScript files -->
<script type="text/javascript"
	src="http://dev.sencha.com/deploy/ext-3.3.1/examples/shared/extjs/App.js"></script>
<script type="text/javascript"
	src="http://dev.sencha.com/deploy/ext-3.3.1/examples/ux/RowEditor.js"></script>

<!-- My JavaScript Files -->
<script type="text/javascript" src="restful.js"></script>
<script type="text/javascript" src="gridValidation.js"></script>
 
<!-- Common Styles -->
<link rel="stylesheet" type="text/css"
    href="http://dev.sencha.com/deploy/ext-3.3.1/resources/css/ext-all.css"/>
<link rel="stylesheet" type="text/css" href="restful.css" />
<!-- Example Styles -->
<link rel="stylesheet"
	href="http://dev.sencha.com/deploy/ext-3.3.1/examples/ux/css/RowEditor.css" />
<link rel="stylesheet" type="text/css"
	href="http://dev.sencha.com/deploy/ext-3.3.1/examples/shared/examples.css" />
<link rel="stylesheet" type="text/css"
	href="http://dev.sencha.com/deploy/ext-3.3.1/examples/shared/icons/silk.css" />

</head>
<body>
<h1>RESTful Editor Grid with Validation</h1>
<h3>About This Example:</h3>
    <div><ul>
    <li>Uses HyperSQL, IBATIS, Spring</li>
    </ul></div>

<div class="container" style="width:500px">
    <div id="user-grid"></div>
</div>
<h3>Tips:</h3>
    <div><ul>
    <li>1. Use Firebug to inspect RESTful operations</li>
    <li>2. Validation rules are modified by editing src/main/webapp/WEB-INF/validation.xml</li>
    </ul></div>

<h3>Steps to Add a new Column:</h3>
    <div><ul>
    <li>1. Add column to the database src/main/resources/ddl.xml</li>
    <li>2. Add column to the grid located in restful.js</li>
    <li>3. Add the new attribute to Item.java Bean (create getters/setters as well)</li>
    <li>4. Change IBATIS config file located in src/main/resources/com/test/ItemDataManager.xml</li>
    <li>5. Optionally Add column validation to src/main/webapp/WEB-INF/validation.xml</li>
    </ul></div>

</body>
</html>

Modify the index.html file and add the link to the above page.

The index.html should look like this.

src/main/webapp/index.html

<html>
<body>
<h3><a href="http://localhost:8080/crud/app/item">Part I - Simple form.</a></h3>
<h3><a href="form.html">Part II - Click here for the ExtJS Form</a></h3>
<h3><a href="grid.html">Part III -Click here for the ExtJS Editor Grid</a></h3>
</body>
</html>

Start Jetty Servlet Engine

mvn clean compile jetty:run

Test the application

Navigate to: http://localhost:8080/crud/ and enter some data

Test the following as well.
1. then shutting down jetty – CTRL-C
2. verify the data survived in the src/main/webapp/WEB-INF/db directory.

Create a WAR file

If you want to run the application in another environment you can create a war file and drop it into a server of your choice. This method will also package up any runtime dependencies and put them in the /WEB-INF/lib folder of the WAR file.

mvn clean compile package

The war file should appear in the target/ folder.

Note: If you have any suggestions to improve the code please send me a comment below. I read every comment and appreciate constructive feedback.

07
Apr
11

Extracting and Tokenizing HTTP Path Variables

This page describes how to extract and tokenizing HTTP path variable(s).

Background

URL Path is often used by RESTful applications to pass scoping information. Applications often parse this information and use it to retrieve data from the server-side.

Modern frameworks like Spring MVC 3 and The RESTlet frameworks have means of extracting tokens from HTTP Path. However if you aren’t using those frameworks then the information on this page will be helpful.

The utility class described on this page will allow you to extract tokens present in URL paths. For example “item/{itemId}/subcomponent/{subComponentId}”

Requirements

  • Maven 2
  • Spring 2.5.6 or above
  • Basic understanding of Struts MVC

Start a new project

mvn archetype:generate -DarchetypeArtifactId=maven-archetype-webapp

groupId: com.test
artifactId: pathVarTest

Answer the rest of the questions with defaults “Just hit the enter key”,

cd to the project base folder.

cd pathVarTest

Since this is a web project maven2 does not create the java source folder.

Create missing folders now.
mkdir -p src/main/java/com/test
mkdir -p src/main/webapp/WEB-INF/jsp

Modify the project Configuration

The pom.xml file should look something like this.

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.test</groupId>
  <artifactId>pathVarTest</artifactId>
  <packaging>war</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>pathVarTest Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring</artifactId>
            <version>2.5.6</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>2.5.6</version>
        </dependency>
        <dependency>
            <groupId>org.apache.geronimo.specs</groupId>
            <artifactId>geronimo-servlet_2.5_spec</artifactId>
            <version>1.2</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.1.2</version>
        </dependency>
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>    
  </dependencies>
  <build>
    <finalName>pathVarTest</finalName>    
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.0.2</version>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.mortbay.jetty</groupId>
                <artifactId>jetty-maven-plugin</artifactId>
                <configuration>
                    <scanIntervalSeconds>2</scanIntervalSeconds>
                    <stopKey>s</stopKey>
                </configuration>
            </plugin>
        </plugins>
  </build>
</project>

PathUtil

The following is where the URL path gets tokenized. It is a static utility class that could be used from a Spring MVC controller or a HTTPServlet Class.

src/main/java/com/test/PathUtil.java

package com.test;

import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Helper class to allow URL path's to be parsed into 
 * EL Expression type tokens.
 */
public class PathUtil {
	public static final Map<String, String> getPathVariables(String patternStr,
			String[] names, String path) {
		String regExPattern = patternStr.replace("*", "(.*)");
		Map<String, String> tokenMap = new HashMap<String, String>();
		Pattern p = Pattern.compile(regExPattern);
		Matcher matcher = p.matcher(path);

		if (matcher.find()) {
			// Get all groups for this match
			for (int i = 0; i <= matcher.groupCount(); i++) {
				String groupStr = matcher.group(i);
				if (i != 0) {
					tokenMap.put(names[i - 1], groupStr);
				}
			}
		}
		return tokenMap;
	}
}

Spring MVC Controller

The following controller class responds to the following URL’s

  • item/{itemId}
  • item/{itemId}/subcomponent/{subComponentId}

src/main/java/com/test/ItemController.java

package com.test;
 
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
 
@Controller
public class ItemController {
 
    @RequestMapping(value="/item/*", method = RequestMethod.GET)
    public String itemInfo(HttpServletRequest request) {
    	final String pattern = "/item/*";
		final String[] names = {"itemId"};
		Map<String, String> pathMap = PathUtil.getPathVariables(pattern, names, request
				.getPathInfo());
   	
		request.setAttribute("pathMap", pathMap);
    	
        return "index";
    }
    @RequestMapping(value="/item/*/subcomponent/*", method = RequestMethod.GET)
    public String subComponentItemInfo(HttpServletRequest request) {
    	final String pattern = "/item/*/subcomponent/*";
		final String[] names = {"itemId", "subComponentId"};
		Map<String, String> pathMap = PathUtil.getPathVariables(pattern, names, request
				.getPathInfo());
   	
		request.setAttribute("pathMap", pathMap);
    	
        return "index";
    }
}

JSP

The following JSP is used to display the Hash Map that contains the results. I haven’t put any work in making it look pretty. Its just functional.

src/main/webapp/WEB-INF/jsp/index.jsp

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
 
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<meta http-equiv="Content-type" content="text/html; charset=iso-8859-1" />
<meta http-equiv="Content-Language" content="en-us" />
 
</head>
<body>
<h3>This are the tokens from the URL Path Info String</h3>
<h3><c:out  value="${pathMap}"/></h3>
</body>
</html>

Web App Configuration

src/main/webapp/WEB-INF/web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">
 
    <display-name>Archetype Created Web Application</display-name>
    <servlet>
        <servlet-name>spring</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    </servlet>
 
    <servlet-mapping>
        <servlet-name>spring</servlet-name>
        <url-pattern>/app/*</url-pattern>
    </servlet-mapping>
</web-app>

Spring MVC Configuration file

This is a pretty standard Spring MVC configuration file.

src/main/webapp/WEB-INF/spring-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
 
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
 
http://www.springframework.org/schema/context
 
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
 
    <context:annotation-config />
    <context:component-scan base-package="com.test" />
 
    <bean
        class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping" />
    <bean
        class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter" />
 
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean> 
</beans>

Test the application

Start the Jetty Servlet Engine to test the application with 1 scoping variable.

  1. Open a command line window and navigate to the project base directory.
  2. Type the following at the command line:
    mvn clean compile jetty:run
    
  3. Navigate to the following URL: http://localhost:8080/app/item/235
  4. You should see the next page which prints “{itemId=235}”.

Test the application with multiple scoping variables.

  1. Navigate to the following URL: http://localhost:8080/app/item/123/subcomponent/456
  2. You should see the next page which prints “{subComponentId=456, itemId=235}”.

Creating a WAR file

If you want to run the application in another environment you can create a war file and drop it into a server of your choice. This method will also package up any runtime dependencies and put them in the /WEB-INF/lib folder of the WAR file.

mvn clean compile package

The war file should appear in the project’s “target/” folder…

That’s all for now!

02
Mar
11

Spring Framework based RESTful Web Service

This page shows you how to quickly and easily create a read-only Spring based RESTful Web Service / Application.

To keep things simple I will not be covering the “front-end” view technologies. Please see one of my other pages on how to get Spring MVC, JSF, extJS or even standard Servlets/JSP’s running with the application discussed here.

You can drop in any “view technologies” once you have the below application running.

The application will retrieve a list of cities from a “mock” datamanager and display them in JSON format in a browser.

The page should take 10-15 minutes to implement.

Requirements

  • Basic understanding of Spring
  • Basic understanding of REST
  • Java 5
  • Maven 2

Procedure

Configure the project

Create a project using Maven archetype. Open up the command prompt and navigate to an empty directory.

mvn archetype:generate -DarchetypeArtifactId=maven-archetype-webapp

groupId: com.test
artifactId: springRestWeb

Answer the rest of the questions with defaults “Just hit the enter key”,

Cd to the project base folder.

cd springRestWeb

Since this is a web project maven does not create the java source foldder.

Create missing directory
mkdir -p src/main/java/com/test

Modify the project configuration file

Open up the pom.xml file and make sure it looks like the one below. In most cases you can just copy and paste the one below into your own.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.test</groupId>
  <artifactId>springRestWeb</artifactId>
  <packaging>war</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>springRestWeb</name>
  <url>http://maven.apache.org</url>
    <repositories>
        <repository>
           <id>maven-restlet</id>
           <name>Public online Restlet repository</name>
           <url>http://maven.restlet.org</url>
        </repository>
    </repositories>
 
  <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>

    <dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
        <version>20090211</version>
    </dependency>        
    <dependency>
      <groupId>cglib</groupId>
      <artifactId>cglib</artifactId>
      <version>2.2</version>
    </dependency>
        
    <dependency>
       <groupId>org.restlet.jee</groupId>
       <artifactId>org.restlet</artifactId>
       <version>2.0.5</version>
    </dependency>
    <dependency>
       <groupId>org.restlet.jse</groupId>
       <artifactId>org.restlet.ext.simple</artifactId>
       <version>2.0.5</version>
    </dependency>
    <dependency>
       <groupId>org.restlet.jee</groupId>
       <artifactId>org.restlet.ext.spring</artifactId>
       <version>2.0.5</version>
    </dependency>
    
    <dependency>
       <groupId>org.restlet.jee</groupId>
       <artifactId>org.restlet.ext.servlet</artifactId>
       <version>2.0.5</version>
    </dependency>
    
    <!-- spring framework -->
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-jdbc</artifactId>
      <version>3.0.1.RELEASE</version>
    </dependency>
        
        <dependency>
            <groupId>org.apache.geronimo.specs</groupId>
            <artifactId>geronimo-servlet_2.5_spec</artifactId>
            <version>1.2</version>
            <scope>provided</scope>
        </dependency>
  </dependencies>
 
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.0.2</version>
                <configuration>
                    <source>1.5</source>
                    <target>1.5</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.mortbay.jetty</groupId>
                <artifactId>jetty-maven-plugin</artifactId>
				<version>7.0.0.v20091005</version>
                <configuration>
                    <scanIntervalSeconds>2</scanIntervalSeconds>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Web Application Configuration

The application uses the “org.restlet.ext.spring.SpringServerServlet” to respond to HTTP Requests. This servlet responds to URL’s that begin with “/app/*” and delegates the handling of the requests to the Resources based on the routing logic specified in the ApplicationContext.xml.

src/main/webapp/WEB-INF/web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">
  <display-name>Archetype Created Web Application</display-name>

<!-- The following is  used to initialize the spring framework when the web app starts. -->
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>
 
     <servlet>
        <servlet-name>stateApplication</servlet-name>
        <servlet-class>
             org.restlet.ext.spring.SpringServerServlet
        </servlet-class>
        <init-param>
			<param-name>org.restlet.application</param-name>
			<param-value>stateApplication</param-value>
        </init-param>
    </servlet>

    <servlet-mapping>
        <servlet-name>stateApplication</servlet-name>
        <url-pattern>/app/*</url-pattern>
    </servlet-mapping>
 
 
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
 
</web-app>

Spring Configuration

The stateApplication uses a router that further checks the URL and calls the proper “Resource” based on the mappings. The routing logic consists of a “url pattern” that will cause the specified “Resource” to be called upon to respond to the request.

Each map entry uses a “SpringFinder” to create an instance of the Resource. The instance of the resource can have any number of beans injected into it (based on spring configuration).

src/main/webapp/WEB-INF/applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
 
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
 
http://www.springframework.org/schema/context
 
http://www.springframework.org/schema/context/spring-context-2.5.xsd">
 
	<bean id="stateDataManager" class="com.test.StateDataManager"/>

	<bean id="stateApplication" class="org.restlet.Application" scope="singleton">
		<property name="root">
			<bean class="org.restlet.ext.spring.SpringRouter">
				<property name="attachments">
					<map>
						<entry key="/state/{name}">
							<bean class="org.restlet.ext.spring.SpringFinder">
								<lookup-method name="create" bean="stateResource" />
							</bean>
						</entry>
					</map>
				</property>
			</bean>
		</property>
	</bean>

	<bean id="stateResource" class="com.test.StateResource" scope="prototype">
		<property name="stateDataManager" ref="stateDataManager"/>
    </bean>
		
</beans>

Create the Resource

The “Resource” is called upon to respond to requests. The “stateDataManager” member will be injected using the spring configuration seen above.

src/main/java/com/test/StateResource.java

package com.test;

import org.json.JSONArray;
import org.restlet.representation.Representation;
import org.restlet.representation.StringRepresentation;
import org.restlet.resource.ResourceException;
import org.restlet.resource.ServerResource;
import org.springframework.beans.factory.annotation.Required;

public class StateResource extends ServerResource {
	// the stateDataManager is injected using Spring
	private StateDataManager stateDataManager;
	
	// ServerResources are thread safe (spring "prototype")
	private String state;
	
    public StateResource() {
        super();
    }
    @Override
    protected void doInit() throws ResourceException {
    	super.doInit();
    	state = (String)getRequestAttributes().get("name");
    }
    @Override
    protected Representation get() throws ResourceException {
    	
        JSONArray jsonArray = new JSONArray(stateDataManager.getCities(state));
        StringBuffer out = new StringBuffer();
        String cb = getQuery().getFirstValue("callback");
        out.append(cb + "(");
        out.append("{ \"totalCount\" : \"" + jsonArray.length() + "\",");
        out.append("\"records\" : ");
        out.append(jsonArray.toString());
        out.append("}");
        out.append(");");
        
        return new StringRepresentation(out.toString());
    }
    @Required
	public void setStateDataManager(StateDataManager stateDataManager) {
		this.stateDataManager = stateDataManager;
	}
	public StateDataManager getStateDataManager() {
		return stateDataManager;
	}
}

Data Manager

This is the dummy data manager. In your situation you would replace the hard coding with a connection to a real database. I have many examples where Spring is used to connect to a mySQL database. Please search for “SimpleJDBC” on the top right corner.

src/main/java/com/test/StateDataManager.java

package com.test;

import java.util.ArrayList;
import java.util.List;

/**
 * This is a test data manager that returns dummy data.
 */
public class StateDataManager {
	public List<String> getCities(String state) {
		// return the list of cities given a state		
		List<String> cityList = new ArrayList<String>();		
		if("TX".equals(state)) {
			cityList.add("Houston");
			cityList.add("San Antonio");
			cityList.add("Dallas");
			cityList.add("Austin");
			cityList.add("El Paso");
			cityList.add("Fort Worth");			
		} else if("NY".equals(state)) {
			cityList.add("New York City");
			cityList.add("Buffalo");
			cityList.add("Rochester");
			cityList.add("Yonkers");
			cityList.add("Syracuse");
		} else if("CA".equals(state)) {
			cityList.add("Los Angeles");
			cityList.add("San Diego");
			cityList.add("San Jose");
			cityList.add("San Francisco");
			cityList.add("Fresno");
		} else {
			// don't add any cities
		}
		return cityList;
	}
}

Test the Application

mvn clean compile jetty:run

Use your browser to navigate to the following URLs:
http://localhost:8080/app/state/CA
http://localhost:8080/app/state/NY
http://localhost:8080/app/state/TX

You should see something like this in your browser:

null({ "totalCount" : "5","records" : ["Los Angeles","San Diego","San Jose","San Francisco","Fresno"]});

The above format is designed to work with the extJS “Ext.data.ScriptTagProxy”. But you can use any number of view technologies to parse and display the data.

Creating a WAR file

If you want to run the application in another environment you can create a war file and drop it into a server of your choice. This method will also package up any runtime dependencies and put them in the /WEB-INF/lib folder of the WAR file.

mvn clean compile package

The war file should appear in the following location…

springRestWeb/target/springRestWeb-1.0-SNAPSHOT.war

28
Nov
10

Invoking a REST method from an Android App

This page describes the process of creating an Android App that obtains and displays a list of countries from a server using a REST method.

Background

If my previous blog I mentioned the process of creating an application that displays a list of countries. Unfortunately the list was hard-coded into the Activity class.

For this page we will refer to a URL that returns JSON data all of countries that we want to display.

Requirements

The JSON Data

The data used for this app is located at the following URL:

https://ext-jsf.googlecode.com/svn/trunk/wordpress/2010/11/countryJSON.do

Project Modifications

Instead of building an application from the  begining we will take the existing app presented here and modify it to get data from the URL above.

Steps We will take

  1. Update AnroidManifest to allow our application to access the device’s internet connection
  2. Add a new method to CountryDataManager to get data using the built in Apache HTTP Client
  3. Modify the Activity Class to call the newly created method
  4. Modify the Adapter to use the default icon in case we don’t have a flag icon for the country

Manifest

Add the highlighted line to the AndroidManifest.xml

	<!-- Add this to request internet access for your application -->
	<uses-permission android:name="android.permission.INTERNET" />

DataManager

Add the following method to the datamanager. The code below uses build in Apache HTTP Client library.

src/com/test/CountryDataManager.java

    public List getCountriesFromServer(){
    	final DefaultHttpClient httpclient = new DefaultHttpClient();
    	final String URL =
            "http://ext-jsf.googlecode.com/svn/trunk/wordpress/2010/11/countryJSON.do";

    	ResponseHandler handler = new ResponseHandler()
    	{
    	    public String handleResponse(
    	            HttpResponse response) throws ClientProtocolException, IOException {
    	        HttpEntity entity = response.getEntity();
    	        if (entity != null) {
    	            return EntityUtils.toString(entity);
    	        } else {
    	            return null;
    	        }
    	    }
    	};

    	List countryList = new ArrayList();
    	try {
            HttpConnectionParams.setConnectionTimeout(httpclient.getParams(), 25000);
    		String response = httpclient.execute(new HttpGet(URL), handler);
    		try {
    			JSONArray jsonArray = new JSONArray(response);
    			int length = jsonArray.length();
    			for(int i=0; i < length; i++) {
    				JSONObject a = (JSONObject)jsonArray.get(i);
    				CountryItem country = parseJSONObject(a);
    				countryList.add(country);
    			}
    		} catch (JSONException e) {
    			throw new RuntimeException(e);
    		}
		} catch (ClientProtocolException e) {
			throw new RuntimeException(e);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
        return countryList;
    }

Activity

Modify line 37 of CountryFlagActivity.java to call the newly created method above.

src/com/test/CountryFlagActivity.java

package com.test;

import java.util.ArrayList;
import java.util.List;

import android.app.ListActivity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.AdapterView.OnItemClickListener;

public class CountryFlagActivity extends ListActivity {

    private CountryAdapter countryAdapter;
    private static final CountryDataManager countryDataManager
    = new CountryDataManager();

    private ProgressDialog m_ProgressDialog = null;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        this.countryAdapter = new CountryAdapter(this, R.layout.row,
                new ArrayList());
        setListAdapter(this.countryAdapter);

        Thread t = new Thread(new Runnable() {
			@Override
			public void run() {
				final List countryList = countryDataManager.getCountriesFromServer();
				runOnUiThread(new Runnable() {
					@Override
					public void run() {
				        for(CountryItem country : countryList) {
				            countryAdapter.notifyDataSetChanged();
				            countryAdapter.add(country);
				        }
				        m_ProgressDialog.dismiss();
				        countryAdapter.notifyDataSetChanged();
					}
				});
			}
		});

        t.start();

        // shows a please wait while the data loads.
        m_ProgressDialog = ProgressDialog.show(CountryFlagActivity.this,
                "Please wait...", "Retrieving data ...", true);

        getListView().setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView parent, View view,
                    int position, long id) {
                Toast.makeText(getApplicationContext(),
                    ((TextView)((LinearLayout) view).getChildAt(1)).getText(),
                        Toast.LENGTH_SHORT).show();
            }
        });
    }
}

Adapter

We don’t have enough flag icon images. The list of countries coming from the server is larger then the original list we had in the previous blog. Therfore if the resource can not be found we will replace it with the default icon.

You can simply replace the getView method with the one seen below.

src/com/test/CountryAdapter.java

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View v = convertView;
        if (v == null) {
            LayoutInflater vi = (LayoutInflater) getContext().getSystemService(
                    Context.LAYOUT_INFLATER_SERVICE);
            v = vi.inflate(R.layout.row, null);
        }
        CountryItem o = items.get(position);
        if (o != null) {
            TextView tt = (TextView) v.findViewById(R.id.toptext);
            if (tt != null) {
                tt.setText(o.getName());
            }
            ImageView im = (ImageView) v.findViewById(R.id.icon);
            if (im != null) {
            	Resources resources = getContext().getResources();
            	int identifier = resources.getIdentifier(
                        "@drawable/" + o.getIsoCode(), "drawable",
                        getContext().getPackageName());
            	if(identifier == 0) {
            		// flag not found. use the default icon.
            		identifier = resources.getIdentifier(
                            "@drawable/icon", "drawable",
                            getContext().getPackageName());
            	}
                im.setImageDrawable(resources.getDrawable(identifier));
            }
        }
        return v;
    }

Run the application

When you run the application you should see a larger list of countries. Also some of the countries will be using the default android icon.

That’s all for now. Feel free to leave comments if you run into trouble.




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