Java Web Services [4/5]: Java API for XML Web Services

Assoc.Prof. Dr. Thanachart Numnondawww.imcinstitute.com

August 2010

Topic 4

Java API for XML Web Services

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Agenda

Java APIs for Web Services

JAX-RPC

JAX-WS

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Java APIs for Web Services

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JWSDP Java Web Services Development Pack (JWSDP) is a free

software development kit (SDK) for developing Web Services

JWSDP has been replaced by GlassFish and WSIT and several components are in Java SE 6.

JWSDP APIs Java API for XML Processing (JAXP), v 1.3

Java Architecture for XML Binding (JAXB), v 1.0 and 2.0

JAX-RPC v 1.1

JAX-WS v 2.0

SAAJ (SOAP with Attachments API for Java)

Java API for XML Registries (JAXR)

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Java API for XML Processing (JAXP)

• JAXP enables applications to parse, validate and transform XML documents.

• Java developers can invoke • SAX parser• DOM parser

• The main JAXP APIs are defined in the javax.xml.parsers package• SAXParserFactory• DocumentBuilderFactory

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Java API for XML Binding (JAXB)

• JAXB allows Java developers to access and process XML data without having to know XML or XML processing.

• JAXB is a Java technology that enables you to generate Java classes from XML schemas by means of a JAXB binding compiler.

• unmarshalling • XML instance documents into Java content trees

• marshalling • Java content trees back into XML instance documents.

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SAAJ (SOAP with AttachmentsAPI for Java™)

• SAAJ provides a convenient API for constructing

and sending SOAP messages without having to

directly create the XML yourself.

• SAAJ was originally part of the Java API

for XML Messaging (JAXM) Separated out from

JAXM 1.0 into JAXM 1.1 and SAAJ 1.1

(SAAJ 1.3 (Java EE 5))

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JAXR

• Standard Java API for performing registry operations over diverse set of registries

� Web service publication & discovery

• A unified information model for describing business registry content

• Provides multi-layered API abstractions

� Level 0: for UDDI

� Level 1: for ebXML registry/repository

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JAX-RPC

• XML data types to/from Java types mapping

• SOAP Message Handler framework

• WSDL to/from Java mapping

• Servlet-based Web service endpoint model

• JAX-RPC Client Programming Models

• Extensible type mapping

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JAX-WS (JAX-RPC 2.0)

• New handler framework

• Metadata-based Web services

• Operational style improvement

• Asynchronous Web services

• Support for non-HTTP transport

• Interoperable attachments (as part of WS-I)

• Secure Web services (as part of Security)

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JAXM

• JAXM is not part of Java EE 5

• JAXM-based asynchronous messaging on Java EE 5 is supported via

� Message-driven Bean (MDB) in EJB 3 can receive both JMS and JAXM message types

� Connector 1.5 allows pluggability of various types message providers (JAXM provider and JMS provider)

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Java APIs for Web Services Protocols

SOAP JAXM 1.0 (JSR 67), SAAJ

JAX-RPC => JAX-WS 2.0 (JSR 224)

WSDL JAX-RPC => JAX-WS 2.0 (JSR 224)

UDDI JAXR 1.0 (JSR 93)

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Sun’s Web Services Stack

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JAX-RPC

Remote Procedure Call (RPC)

RPC, COM, CORBA, RMI:

Synchronous communication: calling process blocks until there is a response

More tightly coupled (than non-RPC model): client must find recipients and know method and its arguments

Non persistent

Client System Server System

Request

Response

Remote Procedure Calls

Protocol Run TimeRun Time

ServantClient

Stub Skeleton

Interface Interface

Common Interface between client and Server Stub for client, Skeleton/Tie for server On-the-wire protocol needs to be agreed upon

RPC Example – Java RMI <<Interface>>Java Remote

Interface

Java Remote Method Protocol (JRMP) isOn-the-wire protocol

Remote ObjectImplementation

RMI ServerSkeleton

RMI ClientStub

rmic compiler

Client

RPC Example - JAX-RPC

Common Interface Service is described in IDL (Interface Description

Language) IDL of CORBA service Java RMI interface in RMI (Language specific) WSDL for Web service

Used by tools to statically or dynamically generate and/or configure interfaces, proxies, and ties in a network technology specific environment

What is JAX-RPC?

Java™ API for XML-based RPC Web Services operations are performed by exchanging

SOAP 1.1 messages

Services are described using WSDL• WSDL is the contract between service provider and

client (only contract needed)

Web service endpoints and clients use JAX-RPC programming model

Key technology for Web Services in the J2EE 1.4 platform

JAX-RPC Design Goals

Easy to use programming model• For both defining & using a service

Hides all the plumbing• You don't have to create SOAP messages yourself

SOAP and WSDL-based interoperability• Interoperate with any SOAP 1.1 compliant peers

Extensibility and Modularity• Support new versions of XML specification, i.e. SOAP 1.2

and beyond• Message handler architecture

JAX-RPC Architecture

Server-side JAX-RPCRuntime System

Container

JAX-RPCService Endpoint

WSDLJava

WSDL Document

HTTP

Client-side JAX-RPCRuntime System

SOAP

Container

JavaWSDLGenerated Code

JAX-RPC Client

JAX-RPC Runtime System

Core of a JAX-RPC implementation:• Library that provides runtime services

for JAX-RPC mechanisms• Implements some of the JAX-RPC APIs

Client side:• Can be implemented over J2SE™, J2EE™ or J2ME™

platforms

Server-side:• J2EE 1.3 or 1.4 Containers: EJB™ or Servlet

Developing a Web Service

tool

Interfaces (java.rmi.Remote type)Must follow JAX-RPC conventions

Implementation classesServlet-based endpoint modelOptional handler and serializer classes

Packaged application (war file)

WSDL Service contract

JAX-RPC : Web Service Endpoint

HTTP

Server-Side JAX-RPCRuntime System

SOAP

Container

JAX-RPC Service Endpoint

WSDL<-->Java

WSDL Document

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JAX-WS

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Quick overview of JAX-WS

Easy way to use Java API for XML Web Services Replace JAX-RPC

Just add @annotation to POJO XML Descriptor free programming

Layer architecture SOAP 1.2 (Document/Literal) Use JAXB for data binding Protocol and transport independence Part of Java SE6 and Java EE 5 Platform

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JAX-WS Layered Architecture

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What Does It Mean?

• Upper layer uses annotations extensively• Easy to use

• Great toolability

• Fewer generated classes

• Lower layer is more traditional• API-based

• For advanced scenarios

• Most application will use the upper layer only

• Either way, portability is guaranteed

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Two ways to create a Web Service

• Starting from a WSDL file> Generate classes using wsimport (=> xjc)

> WS interface> WS implementation skeleton class

> Implement WS interface> Build and deploy

• Starting from a Java class (POJO) > Annotate POJO > Build and deploy

> WSDL file generated automatically

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Start with a Java Class

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Server-Side Programming Model: POJO

1 Write a POJO implementing the service

2 Add @WebService annotation to it

3 Build and Deploy the applicationWSDL is automatically generated at runtime

1 Point your clients at the WSDLe.g. http://myserver/myapp/MyService?WSDL

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Example 1: Servlet-Based Endpoint

@WebServicepublic class Calculator { public int add( int a, int b) { return a + b; }}

• @WebService annotation• All public methods become web service operations

• WSDL/Schema generated automatically• Default values are used

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Service Description Default Mapping• Java mapping => WSDL

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Example 2: EJB-Based Endpoint

@WebService@Statelesspublic class Calculator { public int add( int a, int b) { return a + b; }}

• It’s a regular EJB 3.0 component, so it can use any EJB features

>Transactions, security, interceptors...

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Customizing through Annotations

@WebService(name=”CreditRatingService”, targetNamespace=”http://example.org”)public class CreditRating {

@WebMethod(operationName=”getCreditScore”) public Score getCredit( @WebParam(name=”customer”) Customer c) {

// ... implementation code ...}

}

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Start with a WSDL file

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Generating an interface from WSDL• WSDL => Java generation

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Implementing a Web Service froma Generated Interface

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Server Side Web Service

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JAX-WS uses JAXB for Data Binding

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add() Parameter : Example

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JAXB XML Schema to Java Mapping

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Client Side Programming

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Java SE Client Side Programming

• Point a tool (NetBeans or wsimport) at the WSDL for the service

wsimport http://example.org/Calculator.wsdl

• Generate annotated classes and interfaces

• Call new on the service class

• Get a proxy using a get<ServiceName>Port method

• Invoke any remote operations

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Example : Java SE-Based Client

CalculatorService svc = new CalculatorService();Calculator proxy = svc.getCalculatorPort();int answer = proxy.add(35, 7);

• No need to use factories

• The code is fully portable

• XML is completely hidden from programmer

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Java EE Client Side Programming

• Point a tool (NetBeans or wsimport) at the WSDL for the service

wsimport http://example.org/calculator.wsdl

• Generate annotated classes and interfaces

• Inject a @WebServiceReference of theappropriate type

• No JNDI needed

• Invoke any remote operations

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Example : Java EE-Based Client

@Statelesspublic class MyBean { // Resource injection

@WebServiceRef(CalculatorService.class) Calculator proxy;

public int mymethod() {return proxy.add(35, 7);

}

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Client Side

Annotations Used in JAX-WS

• JSR 181: Web Services Metadata for the Java Platform

• JSR 222: Java Architecture for XML Binding (JAXB)

• JSR 224: Java API for XML Web Services (JAX-WS)

• JSR 250: Common Annotations for the Java Platform

@WebService• Marks a Java class as implementing a

Web Service, or a Java interface as defining a Web Service interface.

• Attributes> endpointInterface> name> portName> serviceName> targetNamespace> wsdlLocation

@WebMethod

• Customizes a method that is exposed as a Web Service operation

• The method is not required to throw java.rmi.RemoteException.

• Attributes> action> exclude> operationName

@WebParam

• Customizes the mapping of an individual parameter to a Web Service message part and XML element.

• Attributes> header> mode> name> partName> targetNamespace

@WebResult

• Customizes the mapping of the return value to a WSDL part and XML element.

• Attributes> header> name> partName> targetNamespace

JAX-WS - Provider

• Web Service endpoints may choose to work at the XML message level by implementing the Provider interface.

• The endpoint accesses the message or message payload using this low-level, generic API

• Implement one of the following> Provider<Source>> Provider<SOAPMessage>> Provider<DataSource>

JAX-WS - Provider

JAX-WS - Dispatch

• Web service client applications may choose to work at the XML message level by using the Dispatch<T> APIs.

• The javax.xml.ws.Dispatch<T> interface provides support for the dynamic invocation of service endpoint operations.

• Similar to Provider on server side

JAX-WS - Dispatch

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Resources

Some contents are borrowed from the presentation slides of Sang Shin, Java™ Technology Evangelist, Sun Microsystems, Inc.

Web Services and Java, Elsa Estevez, Tomasz Janowski and Gabriel Oteniya, UNU-IIST, Macau

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Thank you

thananum@gmail.com

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