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TOTD #4: How to convert a Session EJB to a Web service ?

This TOTD describes how to convert a stateless session EJB to a Web service and uses information from this thread.

1. Add @javax.jws.WebService annotation at the top of your EJB class. The modified code looks like:
   
   @javax.ejb.Stateless
@javax.jws.WebService
public class HelloSessionBean implements server.HelloSessionLocal {
    public String sayHello(String name) {
        return "Hello " + name + " from session bean";
    }
}

The new annotation is shown in this color.
2. Re-build your project and redeploy it.

That's it!

There is no need to specify any additional deployment descriptor or parameters.The WSDL exposed by the EJB Web service endpoint is available at "http://localhost:8080/HelloSessionBeanService/HelloSessionBean?wsdl". The generated WSDL looks like:

<?xml version="1.0" encoding="UTF-8"?>
<!-- Published by JAX-WS RI at http://jax-ws.dev.java.net. RI's version is JAX-WS RI 2.1.2-hudson-182-RC1. -->
<!-- Generated by JAX-WS RI at http://jax-ws.dev.java.net. RI's version is JAX-WS RI 2.1.2-hudson-182-RC1. -->
<definitions
  xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd"
  xmlns:wsp="http://schemas.xmlsoap.org/ws/2004/09/policy"
  xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
  xmlns:tns="http://server/"
  xmlns:xsd="http://www.w3.org/2001/XMLSchema"
  xmlns="http://schemas.xmlsoap.org/wsdl/"
  targetNamespace="http://server/"
  name="HelloSessionBeanService">
  <wsp:UsingPolicy></wsp:UsingPolicy>
  <wsp:Policy wsu:Id="HelloSessionBeanPortBinding_sayHello_WSAT_Policy">
    <wsp:ExactlyOne>
      <wsp:All>
        <ns1:ATAlwaysCapability xmlns:ns1="http://schemas.xmlsoap.org/ws/2004/10/wsat" wsp:Optional="false"></ns1:ATAlwaysCapability>
        <ns2:ATAssertion xmlns:ns3="http://schemas.xmlsoap.org/ws/2002/12/policy"
                         xmlns:ns2="http://schemas.xmlsoap.org/ws/2004/10/wsat" ns3:Optional="true"
                         wsp:Optional="true"></ns2:ATAssertion>
      </wsp:All>
    </wsp:ExactlyOne>
  </wsp:Policy>
  <types>
    <xsd:schema>
      <xsd:import namespace="http://server/" schemaLocation="http://localhost:8080/HelloSessionBeanService/HelloSessionBean?xsd=1"></xsd:import>
    </xsd:schema>
  </types>
  <message name="sayHello">
    <part name="parameters" element="tns:sayHello"></part>
  </message>
  <message name="sayHelloResponse">
    <part name="parameters" element="tns:sayHelloResponse"></part>
  </message>
  <portType name="HelloSessionBean">
    <operation name="sayHello">
      <input message="tns:sayHello"></input>
      <output message="tns:sayHelloResponse"></output>
    </operation>
  </portType>
  <binding name="HelloSessionBeanPortBinding" type="tns:HelloSessionBean">
    <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="document"></soap:binding>
    <operation name="sayHello">
      <wsp:PolicyReference URI="#HelloSessionBeanPortBinding_sayHello_WSAT_Policy"></wsp:PolicyReference>
      <soap:operation soapAction=""></soap:operation>
      <input>
        <soap:body use="literal"></soap:body>
      </input>
      <output>
        <soap:body use="literal"></soap:body>
      </output>
    </operation>
  </binding>
  <service name="HelloSessionBeanService">
    <port name="HelloSessionBeanPort" binding="tns:HelloSessionBeanPortBinding">
      <soap:address location="http://localhost:8080/HelloSessionBeanService/HelloSessionBean"></soap:address>
    </port>
  </service>
</definitions>

Few points to notice:

1. A reasonable set of defaults are chosen for portType/@name, binding/@name, service/@name and even the soap:address/@location. Most of these values can be changed by specifying a different value in the @WebService annotation.

2. Accordingly to EJB 3.0 specification, if @TransactionAttribute is not specified on the method then a default value of REQUIRED is applied. This default value is automatically converted to ATAlwaysCapability and ATAssertion policy assertions.

3. Accordingly to Web Services for Java EE, Version 1.2, webservices.xml is optional so there is no need to write any other deployment descriptor.

4. Be careful not to deploy a WAR file with the context root generated (HelloSessionBeanService) for the Web service endpoint. The EJB Web service endpoint will be inaccessible after that.

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Posted by Arun Gupta in webservices  |  Comments[0]