Direct Web Remoting : DWR

DWR: Direct Web Remoting

Hussain [email protected]

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Believe in coding with style

Blogger(hussulinux.blogspot.com)

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DWR:Agenda

What is DWR? FAQ Advantages Tutorial

DWR: Definition

Easy Ajax for Java. Export your Java code to a browser and include the results in your pages.

DWR:Definition

In other words its nothing butAn RPC library which makes it easy to call Java functions from JavaScript and to call JavaScript functions from Java (a.k.a Reverse Ajax).

Some features

Virtually any data-structure between Java and Javascript (including binary file uploading and downloading)

exception handling advanced CSRF(Cross site request forgery)

protection Integration with Spring and Guice

JS to Java

Java to JS: Reverse Ajax

allows Java code running on the server to find out what clients are viewing certain pages, and to send to them JavaScript, generated either manually or using a Java API

Ingredients

A Java Servlet running on the server that processes requests and sends responses back to the browser.

JavaScript running in the browser that sends requests and can dynamically update the webpage

Dynamic JS

DWR generates dynamic JS based on the Java Classes

The DWR Engine then does some Ajax magic to make it feel like the execution is happening on the browser, but in reality the server is executing the code and DWR is marshalling the data back and forwards.

Advantages

Call Java Functions like RMI or Soap Automatically create Java versions of

JS Expose business methods through JS

Tutorial

Calculator Example What you need? Eclipse Step by Step Run

Calulator Example

We will write a Java class which has the following methods

int add(int a, int b); int subtract(int a , int b); int divide(int a, int b); int multiply (int a, int b);

What you need?

Download DWR.jar from : http://getahead.org/dwr/download

Add the Jar

Add Dependency

Apache Commons:http://commons.apache.org/downloads/download_logging.cgi

Add Jars to Project

Edit the web.xml<servlet> <servlet-name>dwr-invoker</servlet-name> <servlet-class>org.directwebremoting.servlet.DwrServlet</servlet-class> <init-param> <param-name>debug</param-name> <param-value>true</param-value> </init-param></servlet>

<servlet-mapping> <servlet-name>dwr-invoker</servlet-name> <url-pattern>/dwr/*</url-pattern></servlet-mapping>

Write your Business Logic

package org.hussulinux.samples;

public class Calculator {public Calculator() {}

public int add(int a, int b) {return a + b;}

public int subtract(int a, int b) {return a - b;}

public int multiply(int a, int b) {return a * b;}

public float divide(int a, int b) {if (b == 0) {return 0;} elsereturn (float)((float)a / (float)b);}

}

Add dwr.xml along with web.xml

<!DOCTYPE dwr PUBLIC "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN" "http://getahead.org/dwr/dwr20.dtd">

<dwr> <allow> <create creator="new" javascript="Calculator"> <param name="class" value="org.hussulinux.samples.Calculator"/> </create> </allow></dwr>

Open Default page to check

Create front end

index.jsp

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>My First DWR Example</title>

<script type='text/javascript' src='/CalculatorDWR/dwr/interface/Calculator.js'></script> <script type='text/javascript' src='/CalculatorDWR/dwr/engine.js'></script> <script type='text/javascript' src='/CalculatorDWR/dwr/util.js'></script> </head> <body> A:<input type ="text" id="a"><br/> B:<input type ="text" id="b"><br/> <hr/> <br/> <input type ="button" value="Add" onClick="Calculator.add(a.value,b.value,replyfunc)" ><br/> <input type ="button" value="Subtract" onClick='Calculator.subtract($("a").value,$("b").value,replyfunc);' ><br/> <input type ="button" value="Multiply" onClick="Calculator.multiply(a.value,b.value,replyfunc)" ><br/> <input type ="button" value="Divide" onClick="Calculator.divide(a.value,b.value,replyfunc)" ><br/> <script type="text/javascript"> var replyfunc=function(data){ if (data!=null && typeof data=='object') alert(dwr.util.toDescriptiveString(data,2)); else dwr.util.setValue("answerdiv", dwr.util.toDescriptiveString(data,1)); } </script> <hr/> Answer = <div id ="answerdiv"> </div> </body> </html>

Run

Queries

Thanks!

Joe Walker for starting this as open source project

TIBCO for supporting this project You can email me at:

[email protected] Visit: http://hussulinux.blogspot.com