Developing Web Services with the Eclipse Web Tools Platform

David Gallardo

My books• Java Oracle Database Development• Eclipse in Action, (lead author)• Eclipse in Action, 2nd edition due out in December

• Preview article, Introducing the Eclipse Visual Editor available at: http://www.manning.com/books/gallardo2

This presentation available at:

http://www.gallardo.org

What are Web Services?

• Extend the WWW from “The Web for eyeballs” to “The Web for programs”

• Move from Business2User to Business2Business

• Language/platform neutral remote procedure calls built on HTTP infrastructure

Locating a web service

Locating a web service

Publish WSDL

Locating a web service

Query for service

Locating a web service

Obtain WSDL

Using a web service

Call web service operation

Using a web service

Receive result

Web services alphabet soup

Fundamental standards and technologies

• XML – eXtensible Markup Language: The syntax used for Web Service messages, configuration files, description files, etc.

• HTTP – Hypertext Transfer Protocol: The standard transport used to communicate between Web Service servers and clients

• RPC – Remote Procedure Call: The technique of executing a method call remotely—here, the client calling a web service’s operation.

Web Service standards and technologies

• SOAP – Simple Object Access Protocol. An XML-based standard for sending messages (in a SOAP envelope) between web services and clients.

• WSDL—Web Service Definition Language XML-based description of a web services public interface. (Similar to CORBA IDL.)

• UDDI—Universal Description, Discovery and Integration. And XML-based registry for web service. Interrogated with SOAP messages, returns WSDL documents.

Eclipse Web Services Platform

• Provides tools for:– Web applications using JSP/servlets– EJB– Web Service (based on Apache AXIS)– Database exploration

Java Web Service related protocols

• JAXP—Java API for XML Processing• JAX-RPC—Java API for XML-based RPC• JAXR—Java API for XML registries• SAAJ—SOAP with Attachments API for

Java• SAX—Simple API for XML processing• DOM API—Document Object Model API

The rest• We won’t worry about these for now:

DIME—Direct Internet Message EncapsulationHTTPR—Reliable HTTPWSCL—Web Services Conversation LanguageWSCM—Web Services Component ModelWSEL—Web Services Endpoint LanguageWSFL—Web Services Flow LanguageWSML—Web Services Meta LanguageWSXL-Web Services Experience LanguageWSUI—Web Services User InterfaceXLANG—Web Services for Business Process DesignUSML—UDDI Search Markup Language

Eclipse WTP tools for developing a Web Service

• Top down:– You write the WSDL– Eclipse creates the necessary glue classes and

the service’s method stubs in a Java Bean– You implement the operations

• Bottom up:– You create the web service Java Bean– Eclipse creates the glue classes and the WSDL

Demo

• Install WTP from Eclipse.org update site.• Create a web service, bottom-up• Exploring a Web Service using the Web Services

Explorer (ideally http://www.xmethods.com, but here we’ll just use the service we created.)

• Creating a web client for the GoogleAPI web service with WTP.

• Writing our own client.