Apache AXIS2 Web Service Client

This article covers details about writing a web service client using Apache AXIS2 API. The article explains the various API using code snippets and covers parameters require by various methods of web service client API.

Apache AXIS2 web service API mainly consists of two type of objects ServiceClient and OperationClient. ServiceClient provides basic APIs to send and receive SOAP messages, for advanced methods you require Operation Client.

To provide target URL you need to define a EndPointReference type of object.

EndpointReference targetEPR = new EndpointReference(http://localhost:8080/axis2/services/helloworld);

Various options can be given to web service client by creating an Options object. The reference point defined is set into the options along with the Transport protocol.

Options options = new

Options();

options.setTo(targetEPR);

options.setTransportInProtocol(Constants.TRANSPORT_HTTP);

Now create a service client and pass these options to service client using setOptions API of service client.

ServiceClient sender = new ServiceClient();

sender.setOptions(options);

So, till now we have created a service client and provided the various options to it, next step is creating the payload of SOAP message that will be send in the web service call. AXIS2 provides AXIOM (AXIS Object model) to create XML Structure. Following code snippet creates the payload message.

OMFactory fac = OMAbstractFactory.getOMFactory();

OMNamespace omNs = fac.createOMNamespace("http://ws.apache.org/axis2", "");

OMElement method = fac.createOMElement("sayHello", omNs); //Method to be invoked.

OMElement value = fac.createOMElement("parameter1", omNs);

value.addChild(fac.createOMText(value, "Sachin" ));

method.addChild(value);

value = fac.createOMElement("parameter2", omNs);

value.addChild(fac.createOMText(value, "Thapa" ));

method.addChild(value);

Finally use the sendReceive API of ServiceClient to send SOAP request and receive response.

OMElement result = sender.sendReceive(method);

System.out.println(result);

The result object contains the response received from the server.

Deploying Web Service in Apache AXIS2

The purpose of this article is to talk about how to write web service and deploy it in Apache AXIS2.

First step is downloading and installing apache axis2. There are two ways to use Apache AXIS2.

1. Install AXIS2 as a standalone server using the Standard Binary Distribution.
2. Deploy axis2.war and deploy it in a servlet container.

We will be using the 2nd method in the article. To check the installation open the url http://localhost:8080/axis2 and you should be able to see the home page of apache axis2.

Please locate the folder axis2\WEB-INF\services in exploded war file of axis2. This is the folder where you will copy the code of your service and it will get deployed in apache axis2.

Lets us take a simple example. Write your service class.

public class HelloWorld
{
public String sayHello(String firstName, String lastName)
{
System.out.println("Hello World Invoked");
MessageContext incomingContext = MessageContext.getCurrentMessageContext();
FileDataSource dataSource = new FileDataSource("c:/YServer.txt");
DataHandler dataHandler = new DataHandler(dataSource);
incomingContext.addAttachment("contentID", dataHandler);

String data = DataProvider.getData();
return "Hello " + firstName + " " + lastName + " " + data;
}
public String getServiceName()
{
return "test service";
}
}

Write a services.xml file.

<service>
<description>
This is my first service, which says hello
</description>
<parameter name="ServiceClass">HelloWorld</parameter>
<operation name="sayHello">
<messageReceiver class="org.apache.axis2.rpc.receivers.RPCMessageReceiver"/>
</operation>
<operation name="getServiceName">
<messageReceiver class="org.apache.axis2.rpc.receivers.RPCMessageReceiver"/>
</operation>
</service>

In case you want to receive the SOAP payload as XML Message in the service you need to specify XML Message receiver instead of RPCMessageReceiver in services.xml file. To specify XML Message receiver put the following line as child of <operation> tag in your services.xml.

<messageReceiver

class="org.apache.axis2.receivers.RawXMLINOutMessageReceiver"/>

Also, since the service will receive XML Message as input parameter you need to change the signature of the method of service.

public OMElement sayHello(OMElement element)

OMElement object contains the XML Message, OMElement Object is provided by AXIOM. AXIOM stands for AXis Object Model (also known as OM - Object Model) and refers to the XML infoset model that was initially developed for Apache Axis2.


Bundle your class file, services.xml in the hierarchy as shown in the figure below. See helloworld folder in image below.



Copy your service into the services folder of axis2 as shown in figure, start web server. Open the URL http://localhost:8080/axis2.

On the displayed page Click on services, you should be able to see the name of service you specified in services.xml in the list of web services.