Apache Axis: Open Source Web Service Platformpeople.apache.org/~haddadc/presentations/oscon_2004-Axis.pdfApache Axis: Open Source Web Service Platform Chris Haddad Senior Consultant,

Apache Axis: Open Source Web Service Platform

Chris HaddadSenior Consultant, Burton Group

O’Reilly Open Source ConventionJuly 26–30, 2004

Chris Haddad, Senior Consultant, Burton Group

Apache Axis: Web Services Platform

We are

here


• Thesis– Demanding business environment

• Support the virtual enterprise• Access actionable information in real-time• Integrate with 2nd and 3rd tier partners

– Web Service Platform opportunity• Automatic generation of communication bridge• Heterogeneous interoperability

– Platform of choice = Axis• Flexible, extendible, component model• Advanced tooling



• Agenda– Web Services Review– Web Services Platform – Axis Architecture– Axis Advanced– Building Axis clients and services– Get Rolling!



Web Services Review: Service-Oriented Computing


• What is a Web Services Platform?– Tools

• Generate WSDL and proxies• Administer services• Monitor traffic

– Run-time• SOAP Message processing• Service agent invocation

– Management Extensions• Monitoring• Service Provisioning• Security

Web Services Platform

Web services management extensions

Web services platform (tools)• Development• Deployment • Management

Web services platform (runtime)


Web Services Platform: Runtime

Client

Corporate applicationDesktop application

Wireless deviceWeb portal

etc.

Java Application Server

WSDL

SOAPProxy

Web Services Runtime Server

Web services runtime server

Code generated by WS tools

SOAPMessageProcessor

WebService

The application that implements

the service

WS Container

SOAP and WSDL

processing

Application code

DB

Legacy

DeploymentDescriptor(WSDD)


Axis Architecture: Web Services Runtime


Axis Architecture: Detailed View

Administration

Service Dispatch

MSG

Message processing

Handlers

SecurityManagement

Transform

SerializationFramework

DeserializerSerializer

Java Object Configuration Repository

Type Mapping

Flows

FaultResponse

Request

ServiceConfiguration

Transport

HTTP

Web Service

SMTP

BEEP

JMS

ToolsAdminClient

Java2WSDL

WSDL2Java

SOAPMonitor

COMEJBRPC

Security


Axis Architecture: Extension Points


Axis Architecture: Transport

– Interface to network protocol– Accept SOAP requests– Create Message Context– Send SOAP Response

SOAP Request

SOAP Response

MessageContext

TransportListener(http)


Axis Architecture: Message Processing

– Identification of SOAP node’s role and initialize blocks– Map SOAP message to Java objects – Invoke interceptors (chains and handlers)– Process SOAP header directives– Hand-off to service dispatcher

Axis Engine

SOAP Request

SOAP Response

MessageContext


Chain (request)

Handler Handler

Chain (response)

Handler


SOAP Response

SOAP Request

Fault Flow

Request flow

Response flow

Pivot Handler(provider)


– Assignment of processing blocks for SOAP request separated from SOAP response

– Exception processing channel defined by Fault Flow

Axis Architecture: Message Flows


Transport Chains

Global Configuration

Chains

LocalService Chains

– Localize execution of handlers and chains– Header fault check (MU)

Identification of SOAP node

Axis Architecture: Processing Scope

SOAP Response

SOAP Request

Fault Flow

Request flow

Response flow

Pivot Handler(provider)



Axis Engine

Chain (request)

Handler Handler

Axis Architecture: Serialization Framework

– Mapping Java types to/from XML determined by• literal schema or section 5 encoding style. Document and

rpc conventions.• JAX-RPC compliant

– Typical mappings• primitive data types (int, char, float, etc.) • Generic arrays and Java beans• custom serialization

Chain (response)

Handler

MessageContext

SOAP Request

SOAP Response



Best Practice Tips:•Use doc/literal•Avoid collections•Use MSG-style to bypass body serialization


Axis Engine

ServiceEndpoint

ServiceProvider

(rpc)


MessageContext

SOAP Request

SOAP Response


Chain (request)

Handler Handler

Axis Architecture: Service Dispatching

– Load web service agent– Format endpoint call– Execute business logic– Serialize return value as SOAP message

Chain (response)

Handler


Axis Architecture: Deployment Descriptor• Key Elements

– Service Descriptor• SOAP URI• Dispatcher type• Service Java class• WSDL File• Type mappings and handlers

– Handler Descriptor• Logical name• Handler Java class• Configuration parameters

– Type Mapping• XML QName• Java serialization class• Factories

•<deployment>• <handler>• <parameters>• </handler>• <service>• <typemapping/>• </service>•</deployment>


Axis Advanced: Advanced Tooling– Development

• WSDL2Java• Java2WSDL

– Deployment• AdminClient

– Management• Tcpmon• SOAPMonitor


• JAX-RPC: RMI-style API– Application interacts via native Java objects– Standard Java to/from XML mappings– Proxy automatically generates SOAP messages– WSDL-aware

• SAAJ: Low-level API– Application works with SOAP envelope– Attachments

• JWSDL: WSDL API– Used by SOAP runtime and tools (WSDL compiler and generators)– Used with DII

• J2EE Integration– JMS– EJB

Axis Advanced: Supporting Java Standards


Axis Advanced: Client API Choices

– Compiled Stub• Compile time binding• Service interface and proxy specifics defined at compile time

– Dynamic Proxy• Runtime binding• Service interface and protocol specifics defined at compile time

– Dynamic Invocation Interface (DII)• Runtime discovery• Service interface and protocol specifics determined at runtime

– Messaging vs. RPC


Practical Design

– Building a Web Service• Infrastructure handlers

– Security– Session Management– Transformation

• Mapping Types• WSDL Generation

– Building a Client• Proxy code generation from WSDL or DII• Supporting complex types


•Building a new service– Starting points

• Start with code– Follow procedure for an existing application

• Start or follow-up with WSDL– WSDL compiler generates application skeleton– Fill in appropriate application code

– Best Practices• How to encapsulate an application

– Expose it directly– Build a façade, adapter, or wrapper

• Decision criteria:– Does it have an existing API?– What’s the interface granularity?

» Methods» Data Objects

Interoperability Tips

Don’t expose Java-centric objects to SOAP clients

(i.e. turn maps into arrays)

Polymorphism and inheritance can be

dangerous

Building a Web Service


Web Service Components


Building a Web Service Client

– Find WSDL file– Generate client interface– Write the client code

• Use the interface to invoke operations on the remote service


Features Recap

– Component architecture• Flexible configuration options• Multiple extension points (transport, message processing,

encoding)– Advanced tools and utilities

• WSDL and proxy code generation• Service administration• Server-side and Client-side Infrastructure

– Interoperability• Automatic serialization of complex types• Major Web Service and Java standards supported


– Axis Specific• Home http://ws.apache.org/axis• Wiki http://nagoya.apache.org/wiki/apachewiki.cgi?AxisProjectPages• Mailing lists http://ws.apache.org/axis/mail.html

– Interoperability• White Mesa http://www.whitemesa.net• Microsoft SOAP interop http://www.mssoapinterop.org

– Web Services Framework• SOAP1.1 http://www.w3.org/TR/SOAP/• WSDL 1.1 http://www.w3.org/TR/wsdl• XML Schema http://www.w3.org/TR/xmlschema-0/

– Java Web Services• JAX-RPC http://java.sun.com/xml/jaxrpc/• SAAJ http://java.sun.com/xml/saaj/• JWSDL http://www.jcp.org/en/jsr/detail?id=110

Interested in more information?

Documents

Apache Axis: Open Source Web Service Platformpeople.apache.org/~haddadc/presentations/oscon_2004-Axis.pdfApache Axis: Open Source Web Service Platform Chris Haddad Senior Consultant,