XML Schema Data Typing (cont.) - Page 10

Automatically invoking array services

Once you move beyond basic data types, the simple WSDL invocation methods described previously in this chapter no longer work quite as easily. For example, you cannot simply open the GLUE console, pass an array of strings, and hope to receive back an array of doubles. Additional work is necessary, and some manual code is required. Nonetheless, the additional work is minimal, and the discussion that follows focuses on the GLUE platform. We have chosen to focus on the GLUE platform because it represents the most elegant platform for working with complex data types; other tools, such as the IBM Web Services Toolkit, do, however, provide similar functionality.

To get started, you should become familiar with the GLUE wsdl2java command-line tool. The tool takes in a WSDL file and generates a suite of Java class files to automatically interface with the specified service. You can then write your own Java class to invoke the specified service. Best of all, the code you write is minimally simple, and all SOAP-specific details are completely hidden from your view. (See Figure 6-12.)

Figure 6-12. The GLUE wsdl2java tool and the GLUE architecture

Here is the wsdl2java command-line usage:

usage: wsdl2java <arguments>
 
where valid arguments are:
  http://host:port/filename     URL of WSDL
  -c                            checked exceptions
  -d directory                  output directory for files
  -l user password realm        login credentials
  -m map-file                   read mapping instructions
  -p package                    set default package
  -v                            verbose
  -x command-file               command file to execute

Complete information on each argument is available online within the GLUE User Guide at http://themindelectric.com/docs/glue/guide/index.html. For now, we will focus on the most basic arguments. For example, to generate Java class files for the PriceListService.wsdl file, first make sure that the WSDL file is available publicly on a web site or locally via a web server such as Tomcat. Then, issue the following command:

wsdl2java.bat http://localhost:8080/wsdl/PriceListService.wsdl -p com.
   ecerami.wsdl.glue

The first argument specifies the location of the WSDL file; the second argument specifies that the generated files should be placed in the package com.ecerami.wsdl.glue.

GLUE will automatically download the specified WSDL file and generate two Java class files:

write file IPriceList_Service.java
write file PriceList_ServiceHelper.java

The first file, IPriceList_Service.java, is shown in Example 6-7. This file represents a Java interface that mirrors the public methods exposed by the WSDL file. Specifically, the interface shows a getPriceList( ) method that receives an array of String values, and returns an array of double values.

Example 6-7: IPriceList_Service.java

// generated by GLUE
 
package com.ecerami.wsdl.glue;
 
public interface IPriceList_Service
  {
  double[] getPriceList( String[] sku_list );
  }

The second file, PriceList_ServiceHelper.java, is shown in Example 6-8. This is known as a GLUE helper file, and it can dynamically bind to the service specified by the WSDL file. To access the service, simply call the static bind( ) method.

Example 6-8: PriceList_ServiceHelper.java

// generated by GLUE
 
package com.ecerami.wsdl.glue;
 
import electric.registry.Registry;
import electric.registry.RegistryException;
 
public class PriceList_ServiceHelper
  {
  public static IPriceList_Service bind(  ) throws RegistryException
    {
    return bind( "http://localhost:8080/wsdl/PriceListService.wsdl" );
    }
 
  public static IPriceList_Service bind( String url ) 
    throws RegistryException
    {
    return (IPriceList_Service) 
       Registry.bind( url, IPriceList_Service.class );
    }
  }

Once GLUE has generated the interface and helper files, you just need to write your own class that actually invokes the service. Example 6-9 shows a sample application that invokes the Price List Service. The code first calls PriceList_ServiceHelper.bind( ), which then returns an IPriceList_Service object. All subsequent code behaves as if the Price List Service is a local object, and all SOAP-specific details are completely hidden from the developer.

Here is a sample output of the Invoke_PriceList application:

Product Catalog
SKU:  A358185 --> Price:  54.99
SKU:  A358565 --> Price:  19.99

Example 6-9: Invoke_PriceList.java

package com.ecerami.wsdl;
 
import com.ecerami.wsdl.glue.*;
 
/**
 * SOAP Invoker.  Uses the PriceListServiceHelper to invoke
 * SOAP service.  PriceListServiceHelper and IPriceListService
 * are automatically generated by GLUE.
*/
public class Invoke_PriceList {
 
  /**
   *  Get Product List via SOAP
   */
  public double[] getPrices (String skus[]) throws Exception {
    IPriceList_Service priceListService = 
		PriceList_ServiceHelper.bind(  );
    double[] prices = priceListService.getPriceList(skus);
    return prices;
  }
 
  /**
   *  Main Method
   */
  public static void main (String[] args) throws Exception {
    Invoke_PriceList invoker = new Invoke_PriceList(  );
    System.out.println ("Product Catalog");
    String skus[] = {"A358185", "A358565" };
    double[] prices = invoker.getPrices (skus);
    for (int i=0; i<prices.length; i++) {
      System.out.print ("SKU:  "+skus[i]);
      System.out.println (" --> Price:  "+prices[i]);
    }
  }
}

XML Schema Data Typing (cont.) - Page 9
Web Services Essentials
XML Schema Data Typing (cont.) - Page 11