561.  Developing Java Web Services

Rev. 1.5.3

 

This course is now available directly from our partner, Capstone Courseware.

This one-week course prepares Java programmers to develop interoperable Java Web services and using SOAP, WSDL, and XML Schema.  Students get an overview of the interoperable and Java-specific Web services architectures, and then learn the standard APIs for SOAP messaging and WSDL-driven, component-based service development.  Both document-style and RPC-style messages and services are covered in depth.

 

The introductory chapters give overviews of the consensus architecture for interoperable Web services, including the WS-I Basic Profile, and the Java Web services architecture as codified by the J2EE 1.4 specification, including SAAJ and JAX-RPC.  These chapters are meant to be equally useful to developers and non-developers – project managers, analysts, technologists and support staff.  There is a great deal of hands-on demonstration of running Web services, inspecting SOAP traffic, WSDL definitions, and a little bit of Java code, but no Java coding.  The focus is on the architecture itself, and on the roles that various protocols, APIs, tools, and application components play in a working Web service and/or client.

 

The course then gets down to the various brass tacks:  students learn the Simple Object Access Protocol (SOAP) 1.1, and acquire skills in using the SOAP with Attachments API for Java (SAAJ) and the Java API for XML Messaging (JAXM) to build “low-level” SOAP-based Web services and clients, in which the programmer is responsible for element-by-element content of the SOAP message.  Students will learn to read SOAP and to write it by hand, and then will proceed to use the Java APIs to develop servlets that respond to SOAP/HTTP messages.

 

The course then moves to “high-level” services:  component-based development using the Web Services Description Language (WSDL) to define interoperable messaging models and the Java API for XML-Based RPC (JAX-RPC) to automate the SOAP messaging for remote procedure calls between objects.  JAX-RPC abstracts almost all the transport-level implementation – SOAP over HTTP – and this allows the Java developer to concentrate on application and service specifics.  (In this way JAX-RPC is analogous to Java RMI and the EJB architecture:  SOAP/HTTP is treated as nothing more or less than an RPC transport protocol.)  Students get hands-on experience in developing Web services starting either from WSDL descriptors or from existing J2EE applications.  Both servlet and EJB endpoint models are studied, as is the management of SOAP headers using JAX-RPC handler chains.

 

Finally, the course covers advanced techniques including SOAP attachments (using either SAAJ or JAX-RPC), EJBs and JSPs as Web services and clients, and Java Web-service security.

 

LEARNING OBJECTIVES

 

·         Describe the motivation for developing and using Web services in business software.

·         Describe the Web services architecture.

·         Describe common scenarios for Web-service implementation and client-side use.

·         Describe the Java Web services architecture and the requirements of J2EE 1.4.

·         Understand the importance of SOAP to the Web services architecture.

·         Read, understand and write SOAP messages.

·         Understand the role of JAXM and SAAJ in building low-level Java Web services.

·         Build a Java Web service as a JAXM/SAAJ servlet.

·         Implement simple point-to-point SOAP communications from a client application.

·         Mix and match SAAJ, SAX and DOM code in a Web-service implementation.

·         Understand the role of WSDL in providing type information for Web services.

·         Write WSDL documents to describe messages, interfaces and services.

·         Understand the role of the JAX-RPC in the Java Web services architecture.

·         Identify the alternatives for development paths through Java code and WSDL artifacts on server and client sides, and describe the advantages of each.

·         Understand the standard mappings between WSDL, XML Schema and Java.

·         Analyze Java domain models and identify the useful JAX-RPC types.

·         Add a SOAP interface to an existing Java Web application by generating SOAP messaging code using JAX-RPC tools.

·         Build a Java Web service based on an existing WSDL document.

·         Build a Java Web-service client based on a WSDL document.

·         Describe the relationship between the EJB 2.1 and JAX-RPC 1.0 specifications, and how EJBs can implement Web-service endpoints.

·         Add a SOAP interface to an existing system of EJBs, and build an EJB implementation of a Web service based on a predefined WSDL descriptor.

·         Implement a simple Web service using JSP and JSTL XML tags.

·         Implement a JSP Web-service client using custom tags that wrap JAXM.

·         Understand the lifecycle and context of JAX-RPC services as J2EE components.

·         Describe the use of the JAX-RPC message context in managing SOAP headers.

·         Implement a JAX-RPC message handler to adapt an existing Web service.

·         Implement a session-aware JAX-RPC Web service that relies on HTTP sessions based on cookies.

·         Create, send, receive, and read SOAP attachments using SAAJ or JAX-RPC.

·         Describe the various techniques for securing Java Web services available from J2EE and various XML specifications.

 

Duration:  5 days.

 

Prerequisites:

 

·         Solid experience in Java Programming, including object-oriented Java and the Java streams model, is essential to learning to build Java Web services.

·         Some experience with J2EE development, especially Web applications using servlets, will be very helpful, but is not strictly required.

·         Some understanding of XML and XML Schema is strongly recommended. See Courses 501, “Introduction to XML,” and 517, “Introduction to XML Schema.”

·         Various related technology is discussed in the course:  JAXP, SAX, DOM, XSLT, XPath, JSP and JSTL.  None of these is a formal prerequisite for the course, and labs are built to allow students without experience in these things to work through successfully.  Experience in these areas will be helpful, however.

 

1.      Interoperable Web Services

Motivation for Web Services

Evolution of Web Services

HTTP and XML

Interoperability Stacks

Simple Object Access Protocol (SOAP)

Web Service Description Language (WSDL)

Universal Description, Discovery and Integration (UDDI)

The WS-I Basic Profile

REST

 

2.      Building and Hosting Web Services

Hosting Web Services:  Scenarios

SOAP Alone

Service Description

Building Services and Clients from WSDL

Publishing and Discovery

Practical Requirements

The J2EE Reference Implementation

Demonstration:  A Running Web Service and Client

Sniffing SOAP Messages

Development Process

 

3.      The Java Web Services Architecture

Web Services and the J2EE

The Java API for XML Processing (JAXP)

The Java API for XML Binding (JAXB)

The SOAP With Attachments API for Java (SAAJ)

The Java API for XML Messaging (JAXM)

Demonstration:  A SOAP-Based Web Service Using JAXM and SAAJ

The Java API for XML-Based RPC (JAX-RPC)

Demonstration:  A WSDL-Enabled Web Service Using JAX-RPC

WSDL-to-Java vs. Java-to-WSDL

The Java API for XML Registries (JAXR)

 

4.      The Simple Object Access Protocol (SOAP)

SOAP Messaging Model

SOAP Namespaces

SOAP over HTTP

The SOAP Envelope

The Message Header

The Message Body

SOAP Faults

Attachments

XML Schema

Validating Message Content

SOAP Encoding

 

5.      The Java APIs for SOAP Messaging (SAAJ)

The SAAJ Object Model

Parsing a SOAP Message

Reading Message Content

Working with Namespaces

Creating a Message

Setting Message Content

Integration with the DOM and JAXP

 

6.      The Java API for XML Messaging (JAXM)

Building Low-Level Web Services

Messaging Scenarios

Point-to-Point Messaging

JAXM Message Providers

JAXM Servlets

Creating a SOAP Connection

Sending a Message

 

7.      Web Services Description Language (WSDL)

Web Services as Component-Based Software

The Need for an IDL

Web Services Description Language

WSDL Information Model

The Abstract Model - Service Semantics

Message Description

Messaging Styles

The Concrete Model - Ports, Services, Locations

Extending WSDL - Bindings

Service Description

 

8.      The Java API for XML-Based RPC (JAX-RPC)

The Java Web Services Architecture

Two Paths

How It Works - Build Time and Runtime

The Web Services for J2EE Specification

JAX-RPC Deployment

Mapping Between WSDL/XML and Java

Generating from WSDL

Generating from Java

 

9.      Generating Web Services from Java Code

The Java-to-XML Mapping

Primitive Types and Standard Classes

Value Types and JavaBeans

The Java-to-WSDL Mapping

Simple and Complex Types

Arrays and Enumerations

Service Endpoint Interface

Scope of Code Generation

Inheritance Support

Multi-Tier Application Design

Analyzing the Domain

When Things Don't Fit

 

10. Generating Java Web Services from WSDL

The XML-to-Java Mapping

Simple and Complex Types

Enumerations

Arrays

Miscellaneous, Optionally-Supported Constructs

The WSDL-to-Java Mapping

Mapping Operation Inputs and Outputs

Building a Service Client

Locating a Service

Client-Side Validation

Creating a Web Service

Deploying the Service

 

11. Best Practices and Techniques

Which Way to Go?

Interoperability Impact

Controlling Names and URIs

Polymorphism in JAX-RPC

The Dynamic Invocation Interface

Extensible Type Mapping

Passing Objects

Performance Patterns

Another CORBA?

 

12. EJB, JSP and Web Services

Enterprise JavaBeans

Three Tiers for J2EE

EJB 2.1 and JAX-RPC

Session Beans as Web Service Endpoints

The Bean's Service Endpoint Interface

SOAP as an RMI Transport

Adding a SOAP Interface to a Session Bean

Generating From WSDL

"Gotchas"

JSP and XML

The JSTL:  Core and XML Actions

JSP, JSTL and SOAP

Reading SOAP Using XPath

Performing XSLT Transformations

JSPs as Web-Service Clients

Custom Tags for SAAJ and JAXM

 

13. Service Lifecycle and Message Handlers

Web Services as J2EE Components

Service Lifecycle

Component Environment and JNDI

Handling SOAP Headers

Servlet Endpoint Context

EJB Endpoint Context

MessageContext and SOAPMessageContext

Message Handlers and Handler Chains

Processing Model and Patterns

Session Management in JAX-RPC

 

14. SOAP Attachments

SAAJ Object Model, Revisited

The SOAPMessage Class

MIME

The Java Activation Framework

The MimeHeaders Class

The AttachmentPart Class

Adding SOAP Attachments

Identifying Attachments

Reading Attachments

JAX-RPC and Attachments

Generic Mapping for MIME Types

Using Images and Binary Types in Interfaces and Structs

 

15. Security

Web Services and Security

Threats

Technology and Techniques

Public Key Encryption

Digital Signature

J2EE Techniques

Securing Web-Service URIs

HTTPS

XML and SOAP Solutions

XML Encryption and Signature

WS-Security

SAML

XACML

 

Learning Resources

Quick Reference:  W3C and Web-Services Namespaces

Basics of XML and XML Schema

 

 

System Requirements

 

Hardware – minimal:                     1 GHz, 256 meg RAM, 500 meg disk space

Hardware – recommended:           1.5 GHz, 512 meg RAM, 1 gig disk space

Operating system:                          Tested on Windows XP Professional. Course software should be viable on all systems which support the J2EE 1.4 reference implementation.

Software:                                       All free downloadable tools.