• Created by Unknown User (mjarillas), last modified by Unknown User (lmalgeri) on Nov 10, 2005

You are viewing an old version of this page. View the current version.

Compare with Current View Page History

« Previous Version 34 Next »

Overview of the ServiceMix 1.x WSIF Example

Web Services Invocation Framework (WSIF) provides a Java API for calling Web services, hiding the details of how the service is provided, e.g., via SOAP or JMS. This document describes the ServiceMix components that integrate with the Apache Web Service Invocation Framework (WSIF) to perform web service invocations using a number of different implementation protocols such as Axis, local Java, EJB, JMS, JCA and CCI.

The WSIF example shown illustrates the following:

  • an example of declarative programming
  • how to enable a web service to be exposed over a JMS queue through WSIF

This example shows critical code snippets from a larger example, which can be found at: Apache Web Services Project. A client application submits a zip code to a Web Services application via a JMS queue. The web service checks if DSL service is available in the zip code area and responds to the client, also by sending a JMS message. The client software uses WSIF to hide the implementation details of JMS.

In the ServiceMix example, the WSIF API is used by the client to make the zip code request to the web service. The WSIF API takes care of the details of JMS for the client. Other transport mechanisms could have been used by the client as well, such as SOAP, JCA, etc. The ServiceMix WSIF API provides a single API to the client and handles the details of the transmission for the client, simplifying the client code.

The example also shows an important feature of the ServiceMix Client API - how to bind a WSDL file for a web service, which is adorned with WSIF additional metadata to configure the service implementation. In other words, the service.wsdl file has The following snippet is from the servicemix.xml file. Note: that the WSIFBinding class has the service.wsdl file as a property.

Error formatting macro: snippet: java.lang.NullPointerException

Here is an example of how to enable a service to be exposed over a JMS topic or queue. This is a snippet of code from the service.wsdl file. It shows how to configure the JMS binding:

Error formatting macro: snippet: java.lang.NullPointerException

Working with XML versus properties.

The JBI standard requires encoding WSDL 1.1 parts using an XML encoding mechanism. ServiceMix supports this model. However, in addition we also allow the message properties to be used with WSIF as the named parts to avoid unnecessary XML marshalling. For example here is a Java example using the ServiceMix Client API in a WSIF style of working, passing in and fetching out named parameters.

Error formatting macro: snippet: java.lang.NullPointerException

This Java code works against the given WSDL 1.1 service using its named parts. Please see below for the sample WSDL code.

How it Works

The diagram below illustrates the logical flow of the program through the WSIF components:



WSIF Logical Flow Diagram



The logical flow of the program is:

  1. A user opens a web browser and accesses a web form with a "zip code" input field and a submit button. The submit button sends the form and the zip code typed in by the user to a Servicemix HTTP binding component.
  2. The HTTP binding component creates an InOut exchange message through the client API. The message is sent through the NMR to the checkAvailability component.
  3. The checkAvailability component sends the request to the JMS queue.
  4. The web service is implemented with as a message driven EJB (MDB), who's "onMessage" method is listening for messages on the queue.
  5. The MDB, processes the request and sends back a response to the checkAvailability component through a temporary queue. The response is either "true" (DSL service is available) or "false" (DSL service is not available).
  6. The checkAvailability component receives the response from the queue.
  7. The checkAvailability component responds to the HTTP client.
  8. The HTTP client sends the result back to the web form. The value of the result property is displayed and lets the user know whether or not DSL is available in the specified zip code area.

Details

The following table provides more details about the function of the checkAvailability component and the Web Service MDB:

Component or Bean ID

Description

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="e948e720-c6eb-4e0a-9091-4849aa2241a8"><ac:plain-text-body><![CDATA[

checkAvailability

This component uses the WSIFBinding class to integrate WSIF to ServiceMix as specified in the class property. Its definitionResource property is set to read the file classpath:org/servicemix/components/wsif/service.wsdl, which defines the WSDL file that will be used. This file can be found at [servicemix_src_install_dir]\src\test \resources\org\servicemix\components\wsif. In the init() method of the WSIFBinding class, service.wsdl is read to define the binding extension.

]]></ac:plain-text-body></ac:structured-macro>

MDB

This message driven bean is the actual implementation of the service. It acts like a message listener on the queue specified in the config files. When a message is delivered, it extracts the body which is presumably a valid zip code. It then applies some logic to determine whether DSL service is available at this zip code or not. For simplicity, it just returns true for all zip codes < 50000, and false otherwise. The return message is sent to the queue specified in the replyTo field of the request message. Note that the bean must encode the correct JMSCorrelationID in the return message in order for it to be picked up by WSIF.

A code snippet from service.wsdl file:

Error formatting macro: snippet: java.lang.NullPointerException

The following are descriptions of the properties found in the service.wsdl file. These descriptions are quoted from the WSDL Bindings for JMS web page:

  • <jms:address> describes a target port that is accessible via JMS.
  • destinationStyle must either be queue or topic, although only queue is supported at this time.
  • jndiDestinationName is the JNDI name of the JMS queue that WSIF will send requests to.
  • jndiConnectionFactoryName is the JNDI name of the connection factory that WSIF will be used.
  • jndiProviderURL and initialContextFactory specify which JNDI database to use. If they are not present, WSIF uses the default JNDI.
  • jms:binding specifies that this binding is for Native Jms. The type is the type of the JMS message that will be sent. In this case it will be a text message.

Related Documentation

For more information on the following topics please see:

  • No labels