Java(TM) Boutique - Using Apache Axis version 1 to build Web Services

Tutorials : Using Apache Axis version 1 to build Web Services :

Creating the client code

Now it�s time to set up a proper client. We�ll reuse the Swing client from " Struts meets Swing (2)". A few words on this client--it issues the requests through a helper class called WebRequest. Its interface is very much oriented towards the URLConnection class that is used to talk to the Struts servlet, so we cannot use it as it is. We�ll therefore create a new helper class called SOAPRequest, with methods corresponding to the service calls we want to issue, and then change the Swing client code correspondingly.

Here�s a picture of the architecture we want to achieve:

The methods in SOAPRequest are these--note that for simplicity I�ve given them a signature identical to the methods in the DVDService class:

Action	SOAPRequest method
return DVD titles	Vector getTitles()
return DVD details	DVD getDetails(int i)
update DVD	void update(DVD dvd)
create DVD	void create(DVD dvd)
delete DVD	void delete()
save DVDs	void save()

The general layout of a client that talks SOAP is this:

create a Call object (for creating a dynamic RPC call)
set the URL of the web service
define serializers/deserializers for classes
set the name of the method to invoke
set type and data for the input parameters
set the type of the result parameter
issue the call
handle the result

Since we�re transmitting the DVD JavaBean as part of three of our requests we�ll need a serializer and a deserializer for this class. Luckily Axis has a serializer that we can use. You remember that we defined the DVD bean like this in the deployment file:

<beanMapping qname="myNS:DVD" xmlns:myNS="urn:BeanService"
  languageSpecificType="java:hansen.playground.DVD"/>

This gives the bean a QName of [namespace]:[localname] =[urn:Beanservice]:[DVD].

As an example I�ll now sketch the Java code for calling the getDetails service. The numbers in the comments correspond to the numbered list above:

int index = 1;  // DVD number 2

// Create JAX-RPC setup
Service  service = new Service();
Call call = (Call) service.createCall(); // *1*

String endpoint = 
  "http://localhost:8080/axis/services/DVDService";
call.setTargetEndpointAddress( 
  new java.net.URL(endpoint) ); // *2*

// Define the DVD bean
QName qn   = new QName( "urn:BeanService", "DVD" );
call.registerTypeMapping(DVD.class, qn, // *3*
    new org.apache.axis.encoding.ser.BeanSerializerFactory
      (DVD.class, qn),
    new org.apache.axis.encoding.ser.BeanDeserializerFactory
      (DVD.class, qn));

call.setOperationName( "getDetails" ); // *4*
call.addParameter( "arg1", 
  XMLType.XSD_INT, ParameterMode.IN); // *5*
call.setReturnType( qn ); // *6*

DVD dvd = (DVD)call.invoke( 
  new Object [] { new Integer(index) }); // *7*
System.out.println("Results : "); 
System.out.println(dvd.getId() + "/" +  // *8*
    dvd.getTitle() + "/" + 
    dvd.getLength() + "/" + 
    dvd.getActors());

Figure 4: A typical client web service call

In our SOAPRequest helper class we�ll only execute the statements 1-3 once. For each method in SOAPRequest we must therefore write code matching statements 4-8.

Since we reuse the Call object instance every method starts by deleting the previous definition of parameters:

  call.removeAllParameters();

Click to see the complete code for the SOAPRequest class.

In SOAPRequest I�ve coded a main method that tests all the methods. For demonstration purposes several messages are written to System.out, and this is also the case for the DVDService class. So, it�s easy to see if things work the way they were intended to work.

To run the main method you enter these commands in your DOS-window (assuming you�re located in the WEB-INF directory):

  setcp
  cd classes
  java hansen.playground.SOAPRequest

It�s now a simple matter to make some modifications to the Swing client in order for it to use the SOAPRequest class in stead of the WebRequest class. Click to see the complete code for the Swing DVDClient .

To start the client enter:

  java hansen.playground.DVDClient

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