Apache CXF Software Architecture Guide

This Software Architecture Document (web page) document provides an architectural overview of the Apache CXF services framework.

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Table of Contents

Architectural Goals and Constraints

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This extensibility is made possible by dependency injection; the default bus implemenation implementation is based on Springhttp://www.springsource.com/developer/spring Spring Framework, which wires the runtime components together for you.

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• META-INF/cxf/cxf.xml (e.g., in cxf-rt-core only)
• META-INF/cxf/cxf-extension.xml (e.g. in cxf-rt-bindings-soap)
• META-INF/cxf/cxf-property-editors.xml (e.g. in cxf-rt-transports-http)

See Configuration of the Bus for an example of how to customize the bus by supplying your own bean configuration file and Configuration of Runtime Constructed Objects for more information on the special case of injecting into objects created by the runtime (as opposed to objects created by the IOC IoC container itself).

How service calls are processed

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Client Side

Server Side

Front-ends

Front-ends provide a programming model to interact with CXF. JAX-WS, JAX-RS, Simple and Javascript front-end APIs are provided by CXF . Each implementation is cleanly separated from the rest of CXF, just like the bindings and the core. Front-ends provide functionality through interceptors that are added to Services and Endpoints. See also Front-ends

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An interesting feature of the PhaseInterceptorChain is that it is reentrant. This can be powerful and slightly dangerous. This feature is only used in CXF during the sending of an outgoing message, The SoapOutInterceptor is the best example:

public void handleMessage(Message m) {
  writeSoapEnvelopeStart();
  writeSoapBodyStart();

  // invoke next interceptor, which writes the contents of the SOAP Body
  m.getInterceptorChain().doIntercept(m);
  writeSoapBodyEnd();

  writeSoapEnvelopeEnd();
}

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Data bindings implement the mapping between XML elements and Java objects. Data bindings convert data to and from XML, produce XML schema, and provide support for wsdl2java code generation. Not all data bindings support all of this functionality. At very least, a data binding must provide the data conversion. See Data Binding Architecture for details. Currently supported data bindings include JAXB 2.x (default) , Aegis, Apache XMLBeans, Service Data Objects (SDO) and JiBX (under development)and Aegis.

Protocol Bindings

Bindings provide ways to map concrete formats and protocols on top of transports. A binding contains two main parts, a BindingFactory and a Binding. A BindingFactory builds a Binding from the service model's BindingInfo. The binding contains interceptors specific to the binding and also implements the createMessage() method, which creates a Message implementation specific for that binding.

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The Soap binding also adds a special type of interceptor called the SoapInterceptor. The SoapInterceptor adds two methods to the Interceptor class:

Set<URI> getRoles();
Set<QName> getUnderstoodHeaders();

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1. StaxInInterceptor: Creates an XMLStreamReader from an incoming InputStream
2. ReadHeadersInterceptor: Reads the headers into the SoapMessage
3. MustUnderstandInterceptor: Checks the MustUnderstand attributes of all the headers against all the SoapInterceptor's getUnderstoodHeaders method.
4. SoapOutInterceptor:

Additional Bindings

Other bindings include REST/HTTP

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Pure XML Binding

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CORBA Binding

...binding, pure XML binding, and the CORBA binding.

Transports

CXF includes its own transport abstraction layer to hide transport specific details from the binding and front end layers. Currently supported transports include: HTTP, HTTPs, HTTP-Jetty, HTTP-OSGI, Servlet, local, JMS, In-VM and many others via the Camel transport for CXF such as SMTP/POP3, TCP and Jabber. Learn more about transports here.

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Destinations are the basis for receiving incoming messages. A destination is created from a DestinationFactory:

DestinationFactoryManager dfManager = bus.getExtension(DestinationFactoryManager.class);

// Find a DestinationFactory for the SOAP HTTP transport
DestinationFactory df = dfManager.getDestinationFactory("http://schemas.xmlsoap.org/wsdl/soap/http");

// TODO: outline building of EndpointInfo
EndpointInfo endpointInfo = ...;
Destination destination = df.getDestination(endpointInfo);

MessageObservers can then be registered with Destinations. These listen for incoming messages:

MessageObserver myObserver = ...;
destination.setMessageObserver(myObserver);

The most common MessageObserver used in CXF is the ChainInitiationObserver. This takes the incoming message, creates a message Exchange & PhaseInterceptorChain, then starts the chain.

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A JAX-WS example

Here's a small example of what might happen when we publish a service via the JAX-WS Endpoint.publish() method.

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Dependencies

CXF's dependencies

Tooling

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Build Support

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Deployment View

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Size and Performance

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Quality

CXF's Software Quality approach is detailed here.

Appendix

Definitions, Acronyms and Abbreviations

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References

• Software Architecture, Wikipedia
• Sample S/W Architecture Document, Rational Software Corporation
• Documenting your Software Architecture, by Jim Alateras (March 2006)