Table of Contents
This chapter describes the concept of a web service transaction and how to configure it.
Transaction is a fundamental concept behind the implementation of reliable distributed applications. This mechanism ensures that all transaction participants receive the same result.
In essence, a transaction is characterized by the ACID properties.
To control the operation and result of an application, a web service environment needs to provide the same coordinated behavior that is provided by the traditional transaction mechanism. It also requires a functionality that coordinates the processing of results from multiple services which requires a more flexible type of transaction.
The following are the transaction specifications supported by JEUS 7 web services.
These transaction specifications provide a WSDL definition for such coordinated behavior.
A web service transaction for a server application is defined in a WSDL or Java class.
To create a web service transaction in WSDL, define a web service policy in the WSDL document and use it to create a web service through the wsimport tool.
To define a web service transaction in a WSDL file according to the web service policy, set the PolicyAssertion property as in the following.
<wsat200410:ATAssertion xmlns:ns1="http://schemas.xmlsoap.org/ws/2002/12/policy" />
The following WSDL file defines a web service transaction.
[Example 16.1] << AddNumbers.wsdl >>
<?xml version="1.0" encoding="UTF-8"?>
<definitions name="AddNumbersService" targetNamespace="http://server.fromwsdl/"
xmlns:tns="http://server.fromwsdl/" xmlns="http://schemas.xmlsoap.org/wsdl/"
xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/
oasis-200401-wss-wssecurity-utility-1.0.xsd"
xmlns:wsp="http://www.w3.org/ns/ws-policy"
xmlns:wsp1_2="http://schemas.xmlsoap.org/ws/2004/09/policy"
xmlns:wsam="http://www.w3.org/2007/05/addressing/metadata"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<wsp:Policy xmlns:wsat200410="http://schemas.xmlsoap.org/ws/2004/10/wsat"
wsu:Id="AddNumbersPortBinding_addNumbers_WSAT_Policy" wsp:Name="">
<wsat200410:ATAssertion
xmlns:ns1="http://schemas.xmlsoap.org/ws/2002/12/policy"
wsp:Optional="true" ns1:Optional="true" />
</wsp:Policy>
<types>...</types>
<message>...</message>
<portType>...</portType>
<binding name="AddNumbersPortBinding" type="tns:AddNumbers">
<soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="document" />
<operation name="addNumbers">
<wsp:PolicyReference URI="#AddNumbersPortBinding_addNumbers_WSAT_Policy" />
<soap:operation soapAction="addNumbers" />
<input>
<wsp:PolicyReference URI="#AddNumbersPortBinding_addNumbers_WSAT_Policy" />
<soap:body use="literal" />
</input>
<output>
<wsp:PolicyReference URI="#AddNumbersPortBinding_addNumbers_WSAT_Policy" />
<soap:body use="literal" />
</output>
</operation>
</binding>
<service>...</service>
<definitions>
To configure a web service transaction in a java class, add the following annotation in the web service endpoint implementation class.
@com.sun.xml.ws.api.tx.at.Transactional(version=com.sun.xml.ws.api.tx.at.Transactional.Version.WSAT10)
The following is an example of defining a web service transaction in a java class.
[Example 16.2] << AddnumbersImpl.java >>
@WebService
@com.sun.xml.ws.api.tx.at.Transactional(
version=com.sun.xml.ws.api.tx.at.Transactional.Version.WSAT10)
public class AddNumbersImpl {
...
}
There are no additional settings for web service transaction on the client side. The client applications that invoke the web service automatically provides a web service transaction environment at runtime by remotely reading the web service transaction policy from the WSDL.
To use a web service transaction, a coordinator service that tunes the transaction activities between participants must be deployed. A coordinator service is required for both server and client applications. Only one coordinator service must be deployed when a web service and a web service client are running on the same server.
The 'wstx-services.ear' file for coordinator service is in the following path.
JEUS_HOME/lib/systemapps
Web service transaction implementation using a Java class is the same as the implementation of other basic JEUS web services, except that it requires adding the @com.sun.xml.ws.api.tx.at.Transactional annotation.
Java Transaction API(JTA) is used to implement a web service transaction on a web service client.
[Example 16.3] << AddNumbersClient.jsp >>
InitialContext ctx = new InitialContext(); UserTransaction utx = (UserTransaction) ctx.lookup("java:comp/UserTransaction"); AddNumbersImplService service = new AddNumbersImplService(); AddNumbersImpl port = service.getAddNumbersImplPort(); utx.begin(); int result = port.addNumbers(number1, number2); utx.commit();