Java Web Services Slides 20011107

Building Web Services in Java Andy Longshaw Blue Skyline [email protected]

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Some important questions • Who am I? • Who are you? – Developers and technical architects wanting to build Java-based Web Services

• Why are you here? – – – –

Creating Java-based Web Services Mapping between WSDL and Java Use of SOAP from Java Deployment and use of a Java-based Web Service

– Demos using IBM WSTK, Apache SOAP and Apache Axis © Blue Skyline Ltd

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Web Services in Java motivation • What do we mean by "Web Service"? • Why use Web Services? • Why use Java?

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Developer view of Web Services • Extension of component model onto the Web – Your applications rely on 3rd party "components" – Component functionality is hosted remotely – Solution code calls on functionality as necessary

• Service-oriented view – Locally installed components are more like libraries – Sliding scale of business<->infrastructure services

• Standards are defined/emerging – WSDL/SOAP/UDDI – ebXML © Blue Skyline Ltd

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Benefits of Java Web Services • Why use Web Services? – – – –

Language- and platform-neutral framework Component drivers: faster development Potential easing of application integration The vendors are pushing you that way

• Why use Java? – – – –

One of the principal developer languages Lots of activity around Java Web Services Java-based Web Services are portable You like Java!

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Developing with Web Services • • • • • •

What steps do I need to follow? What APIs are there? Creating a Web Service Deploying a Web Service Using a Web Service What tools are there to help me?

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Web Service roles • •

What do I need to do? Service providers – – – – –

•

Service users – – – –

•

Have a good idea for a service! Implement the service being offered Describe the service being offered Publish the description Wait for customers Discover an interesting service Retrieve the description Plug it into your application Use the service

Must have a framework for all this to take place under otherwise it is chaos © Blue Skyline Ltd

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Where are you starting from? • Steps and tools required depends on your situation • The functionality already exists – EJB, servlet or Java class – Need to wrap the existing component as a Web Service

• The functionality is new – Create a new Web Service from scratch… – … or write it as an EJB/servlet/class and wrap it

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Architecture Candidate Web Services

Web Service Client

Java methods Web Web Service Service Proxy Proxy

SOAP Request

SOAP Router & Dispatcher

Invoke target method

SOAP Response

servlets

EJBs

servlet

WSDL WSDL © Blue Skyline Ltd

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Describing a Web Service • Create a Web Service Description Language (WSDL) document • WSDL describes possible operations… – messages, parameters, return values, complex types

• …and how to access them – binding information, ports, portTypes

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Creating a WSDL document • Create the document by hand… • Automatic generation from an existing class – Example: IBM WSTK WSDL Generator Tool (wsdlgen) • wraps EJBs, classes or COM dispinterfaces • Uses SOAP 2.2 functionality under the covers

• Define your business operations and generate WSDL from them – Completely Java-independent

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Creating the Web Service • If WSDL was generated from an existing class, skip this step • If WSDL is new, need to generate Java "skeleton" – Example: IBM WSTK Service Implementation Template Generator Tool (servicegen) • Creates Java interface from WSDL • WSDL message names are mapped to Java methods • Service class implements interface – Example: Axis Wsdl2java

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Deploying the Web Service • Service must be deployed to endpoint(s) defined in WSDL • Server-side proxy must – – – – –

listen on endpoint process SOAP message and unmarshal parameters route messages to correct Java method capture return value(s) and marshal them back Example: IBM WSTK servicegen and wsdlgen • Both create deployment descriptor for target environment, e.g. Apache SOAP – Example: Apache ServiceManagerClient to deploy

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Complex datatypes • Need to marshal between WSDL/SOAP datatypes and Java types – Mapping of Java types corresponding to XML Schema data types is simple – Complex and custom types need specific marshaling

• Again, tool generation of Java classes is preferable – Example: IBM WSTK wsdlgen and servicegen • Generates Java serializer classes for use with target client and server, in this case Apache – Example: Use of bean serializer in Axis

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Creating a Java client proxy • Use a client-side proxy to hide SOAP complexity – Proxy implements same methods as server

• Best option is for tool to generate proxy – Example: IBM WSTK Service Proxy Generator Tool (proxygen) • Generates proxy and serializers – Example: Axis Wsdl2java

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Using the Java Proxy • Instantiate and call client-side proxy • Relatively little Web Service-specific code needed – Address and location – Complex type conversion

• Caveats – Network latency – Error handling – Style of calls

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Alternative clients • You may have other clients – Direct SOAP clients in Java – Calls from non-Java clients

• Direct SOAP clients – Read and understand the WSDL :-(

• Clients in other languages – Use the WSDL to generate a proxy (e.g. C#) – This is the whole point of it!

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Dynamic lookup • Fully dynamic Web Services model has service information retrieved from UDDI registry • Now things get a bit trickier… • There is no standard Java API to access UDDI – Currently some vendor-specific solutions, e.g. UDDI4J – See JAXR later

• There is no standard Java API to access WSDL – Currently some vendor-specific solutions, e.g. WSDL4J – See JSR110 later

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Registering the service • WSDL information in two parts – Interface definition: reusable general description – Implementation definition: specific endpoints

• tModel represents interface definition – tModel structure points to WSDL document – tModel registered separately from implementation info – tModel has unique key

• Service creator builds UDDI businessService – Contains bindingTemplates which reference tModels – Stored under businessEntity – save_service, save_binding, save_tmodel © Blue Skyline Ltd

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Retrieving the service information • Search UDDI registry for information… – find_business, find_service, find_binding, find_tmodel – Returns relevant XML structure(s)

• … or retrieve specific binding – Obtain bindingTemplate details via get_bindingDetail – Provide unique key to identify entry required

• Parse and use XML returned • A good case for using vendor-specific APIs! – Or waiting until JAXR appears © Blue Skyline Ltd

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IBM WSTK • Version 2.4 features and functionality – – – – – –

Tools and utilities Java WSTK API to simplify things a bit SOAP UDDI4J WSDL4J Binds to servlet container, e.g. Tomcat or WebSphere

• See also IBM's XML and Web Services Development Environment

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Apache SOAP • Version 2.2 features and functionality – Supports SOAP 1.1 and SOAP Messages with attachments – Java API for invoking SOAP RPC services – Java API for sending and receiving SOAP messages – Expose Java classes as SOAP RPC servers – Create SOAP message servers in Java – Supports HTTP and SMTP transports – Plug it into a servlet container, e.g. Tomcat

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Apache Axis • Next generation Apache SOAP – Alpha 2 release Sept 2001

• Improved performance • Improved deployment – JWS files – Heading to Web Service Deployment Descriptor (WSDD)

• WSDL support – Wsdl2java tool creates stubs and skeletons – ?wsdl suffix on service URL presents WSDL to caller © Blue Skyline Ltd

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Other Tools • Web Service capabilities in IDEs and Tools – – – – – –

Forte for Java 3.0 Together Control Center 5.5 Visual Age WebGain Jbuilder CapeClear (Studio and Connect)

• Web Service capabilities in App Servers – – – –

WebLogic 6.1 WebSphere 4.0 iPlanet Oracle 9i

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The JAX Pack: JAX-RPC • Essentially a Java binding for RPC over SOAP • Feed WSDL description into compiler – – – –

Produces stubs and skeletons Java mappings for complex types APIs for invocation, marshaling etc. Forwards and reverse mappings

• Looks very similar to existing support from IBM WSTK and seems to be tracked by Apache Axis • JCP JSR101 still in progress (Sept 2001) – Public spec 10th October 2001 (0.5 release) – No EA release as yet © Blue Skyline Ltd

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The JAX Pack: JAXM • Document-centric SOAP-based messaging – Synchronous – Asynchronous

• Profiles for specific messaging systems – ebXML is the notable one – JAXM began life as a mapping for ebXML

• JCP JSR067 close to completion (Sept 2001) – Spec. publicly available

• Early access release available (EA2) – Raw SOAP messaging capability – Sample profile for ebXML © Blue Skyline Ltd

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The JAX Pack: JAXR • Generic XML-based registry access – UDDI – ebXML Registry – Others, including eCo Framework, ISO 11179

• Multiple levels of registry – Business and generic – Specific mappings for UDDI and ebXML Registry

• JCP JSR093 still in progress (Sept 2001) – Spec. publicly available – No EA release © Blue Skyline Ltd

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What's next: Java • • • • • • • •

JAX Pack delivery in J2EE 1.4 (JSR151) JSR110: WSDL API JSR109: Programming model for Web Services JSR156 XML Transactioning API for Java (JAXTX) JSR155 Web Services Security Assertions JSR105: XML Dsig JSR106: XML Encryption JSR157: ebXML CPP/A APIs for Java © Blue Skyline Ltd

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What's next: Web Services • Current state of standards – Many still in formative stages – XML Protocol (XMLP) to upgrade SOAP

• Higher-level metadata – Business process integration and business objects – Web Service Flow Language (WSFL) – Automatic code generation

• End-to-end security – XML Digital Signature

• Context propagation © Blue Skyline Ltd

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Summary • Web Services extends component model onto the Internet • Java is a good language for building Web Services – Lots of activity around the combination – Portable implementations

• We are only just coming out of the "banging rocks together" stage

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Further information • Java Community Process – http://www.jcp.org

• Sun – http://java.sun.com/j2ee/webservices/index.html

• IBM – http://www-106.ibm.com/developerworks/webservices/

• Apache XML – http://xml.apache.org/soap/index.html

• Web Services Architect – http://www.webservicesarchitect.com/

• Web Services Portal – http://www.webservices.org

• ebXML home and resources – http://www.ebxml.org © Blue Skyline Ltd

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An alternative approach • OASIS and UN/CEFACT joint venture – http://www.ebxml.org

• Creating the framework – Initial 18 month project to create standards – Use existing technology where possible

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Components identified Technical Architecture

Registry And Repository

Core Components

Business Process Modelling

Collaboration Protocol

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Messaging

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Company A

How it works

1

<XML>

Business components Business scenarios Business profiles

Request Business Details

2 3 ebXML registry

Implement System

Register Implementation Details and Co. A profile

4 Download scenarios and profiles

Query for Co. A profile

Agree business arrangement

5

6 Do business transactions

Company B © Blue Skyline Ltd

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ebXML and Web Services • How does ebXML fit with the world of Web Services? • UDDI can be used to locate appropriate CPP – Will all CPP info really be stored in global UDDI registry? – If not, need a second tier

• SOAP provides some wire-level compatibility – However, you lose security and reliability extensions defined in ebXML message

• Other parts largely overlap – WSDL and CPP/CPA – UDDI and Registry & Repository © Blue Skyline Ltd

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