JAX-RPC

JAX-RPC

It stands for Java API for XML-based RPC. JAX-RPC is a technology for building web services and clients that use remote procedure calls (RPC) and XML. Often used in a distributed client-server model, an RPC mechanism enables clients to execute procedures on other systems.

With JAX-RPC, clients and web services have a big advantage: the platform independence of the Java programming language. In addition, JAX-RPC is not restrictive: a JAX-RPC client can access a web service that is not running on the Java platform, and vice versa. This flexibility is possible because JAX-RPC uses technologies defined by the World Wide Web Consortium (W3C) such as:

SOAP defines message format

WSDL describes the various services offered by web service application as xml

file

XML Schema – defines data types used in WSDL doc.

Writing Web Service using JAX-RPC (Currency Converter):

These are the basic steps for creating the web service and client:

1. Create an interface

2. Code the implementation class.

3. Use wscompile to generate wsdl doc.

4. Create deployment descriptor file

5. Package the files into a WAR file.

6. Deploy the WAR file.

7. Create a client file to access the web service

8.  Use wscompile to generate and compile the web service artifacts needed to connect to the service.

9. Compile the client class.

10.            Run the client.

Example for Creating Web service software:

To write web service using JAX-RPC, we need JWSDP(Java Web Server Development Package). This package has wscompile and wsdeploy tools.

wscompile is used to convert java file into wsdl file whereas wsdeploy is used to package our web service.

To Create a web server file:

Create a directory in the name of CurrencyConverter and create a sub director myCurCon under WEB-INF/Src folder

Step 1: Create a service end point interface

Rules for creating service end point interface are as follows:

1. The interface must extend java.rmi.Remote interface

2. Every method in this interface must throw java.rmi.Remote exception

3. Every method return type and its parameter data type in this interface must be java primitive data types

4. The interface must not contain any public static final declarations.

package myCurCon;

public class ExchangeValues

{

public docuble dollars; public double euros; publci doubel yens;

}

package myCurCon;

public interface CurCon extends java.rmi.Remote

{

public ExchangeValues fromDollars(double dollars) throws java.rmi.RemoteException;

public ExchangeValues fromEuros(double dollars) throws java.rmi.RemoteException;

public ExchangeValues fromYens(double dollars) throws java.rmi.RemoteException;

}

Step 2: Create a class to implement this interface public class CurConImpl implements CurCon

{

public   ExchangeValues fromDollars(Double               Dollars)      thorws

java.rmi.RemoteException

{

ExchangeValues ev=new ExchangeValues(); ev.dollars=dollars;

ev.euros=dollars*100;

ev.yens=dollars*200; return ev;

}

}

Step 3: Compile using javac to create respective classes for ExchangeValues.java, CurCon.java and CurConImpl.java

Step 4: Use wscompile to create WSDL doc. Inputs to wscompile are supplied via the following configuration file called config.xml file.

<? xml version="1.0" ?> <configuration xmlns="url" >

<service name="HistoricCurrencyConverter" targetNameSpace="url" typeNameSpace="url" packageName="myCurCon">

<interface name="muCurCon.CurCon" /> </service>

</configuration>

- Save this file as config.xml and use the following command to create wsdl doc.

wscompile –define – d WEB-INF –classpath WEB-INF/classes – model WEB-INF/model.xml.gz config.xml

-d specifies the directory to receive the generated wsdl doc. which will be named as Historic Currencyconverter.wsdl

Step 5: Create another configuration file called jaxrpc-ri.xml which is used as deployment descriptor file as shown below

<? xml version="1.0" ?>

<webServices xmlns="url" targetNameSpace="url" typeNameSpace="url" urlPatternBase="/converter" >

<endpoint name="CurrConverter" displayName="Currency Converter" description="Converts b/w dollars, yens and euros" interface="myCurCon.curCon" model="/WEB-INF/model.xm.gz" implementation="myCurCon.CurConImpl"/> <enpointMapping endPointName="CurrConverter"

urlPattern="/Currency" /> </webServices>

The tag <endpoint> gives the information to web server including name of the service end point interface, implementation file model generated by wscompile etc.

Step 6: Package and deploying the web service created Create WAR(Web Archive) file. Add the deployment descriptor and service files to the WAR file. The following command is used:

jar cf converter-temp.war WEN-INF

Deploy the war file using the following command wsdeploy –o converter.war converter-temp.war

Step 7: Start tomcat server

Step 8: Browse to http://localhost:8080/Converter/Currency to see the status of the currency converter web service. The output will be:

To write a client program

To access the currency converter web service it is necessary to have a java client program

Step 1: Create xml file named config.xml <? xml version="1.0" ?>

<configuration xmlns="url" wsdl location =http://localhost:8080/Converter/Currency?wsdl packageName="myCurConClient" />

</configuration

Step 2: Use wscompile to load wsdl from the url specified in the location attribute of config.xml. Use the following command for that wscomplie –gen –keep –d classes –s src config.xml

This instructs to generate a class file from the wsdl and keep the java source file in src

folder.

Step 3: Create java client program for accessing the web services as shown below package mycurConClient;

public class CurConBean

{

private double value=1.0;

private String Currency="dollars"; public void setValue(double value)

{

this.value=value;

return;

}

public void setCurrency(String currency)

{

this.currency=currency;

return;

}

public ExchangeValues getExValues()

{

ExchangeValues ev=null;

CurCon=(new HistoricCurrencyConverter_impl().getCurConPort()); try

{

if(currecny.equals("euros")

{

ev=curcon.fromEuros(value);

}

else if(currency.equals("yens")

{

ev=curcon.fromYens(value);

}

}catch(Exception e){} return ev;

}

}

Step 4: Compile using javac

Step 5: Create a jsp for using this bean class to perform a currency conversion class and display the result in a HTML file

<html>

<jsp:useBean id="client" class="myCurConClient.CurConBean" /> <body>

<%

String value=request.getPArameter(val); %>

<jsp:setProperty name="client" property="Currency" value="curr" /> <jsp:setProperty name="client" property="Currency" value="cur" /> Converted amount:

</jsp:getProperty name="Client" property=ExValue" /> </body>

</html>

Step 6: In the browser location bar type http://localhost:8080/ConverterClient/Conver.jspx?cur=”euros” val=”500.30”

This invokes the web service from the server and converts the euros value 500.30 to equivalent dollars and yens value and displays the result.