An Overview of Java Web Services in Java Deploy bar code 39 in Java An Overview of Java Web Services

An Overview of Java Web Services use awt 3 of 9 barcode generation toget code 39 full ascii on java iPhone 2.3.12 Asynchronous Invocation JAX-WS adds asynchronous su pport to the invocation model de ned by JAX-RPC 1.1. This is a big step forward for enterprise Java, since asynchrony is a fundamental requirement for SOAP.

Even better, however, is the fact that JAX-WS supports two models for asynchronous request-response messaging: polling and callback. Polling enables client code to repeatedly check a response object to determine whether a response has been received. Alternatively, the callback approach de nes a handler that processes the response asynchronously when it is available.

Asynchronous callback is much like de ning a listener on a Java Message Service (JMS) [JSR 914] temporary message queue to handle responses that come in asynchronously. The listener is invoked when the responding service calls back with the response. Polling is analogous to checking the temporary queue periodically as you wait for the response to arrive.

. 2.3.13 One-Way Operations JAX-WS 2.0 supports mapping Java methods to WSDL one-way operations. This is an important feature because it enables re and forget style messaging similar to JMS, but based on SOAP over HTTP.

One-way operations pave the way for developers to add support for reliable messaging protocols (e.g., Web Services Reliable Messaging [WS-RM]).

Reliable messaging would enable JWS to be used as a platform for creating loosely coupled applications based on messaging-style Web Services a key goal of SOA design.. 2.3.14 Client-Side Thread Management An instance of ncurrent.

Executor can be set on a JAX-WS client (i.e., an instance of javax. to provide custom thread control.

This allows the developer to control thread creation and usage when doing asynchronous Web service invocation. One use case for this capability is to implement custom thread pooling to enhance performance. See Section 2.

3.12 for more on asynchronous invocation..

2.3.15 WSDL Styles Support for RPC/Literal and Document/Literal Wrapped JAX-WS delegates serializat ion to JAXB. However, to package the serialized parameters into a SOAP message, JAXB needs some guidance from JAXWS. That guidance depends on the WSDL style used by the deployed Web.

JAX-WS 2.0 service and that style is d etermined when the service is deployed. For example, the parameters could be packaged as individual children of the SOAP body element (unwrapped), or they could be wrapped into a single element child of the body (wrapped). JAX-WS supports the two most popular, WS-I-compliant, WSDL styles: rpc/literal and document/literal wrapped.

19 The rpc/literal style is called RPC by the JAX-WS speci cation.20 It is speci ed by using a javax.jws.

SOAPBinding annotation with the following properties: a style of RPC, a use of LITERAL, and a parameterStyle of WRAPPED. The document/literal wrapped style is called Document Wrapped by the JAX-WS speci cation.21 It is speci ed by using a javax.

jws.SOAPBinding annotation with the following properties: a style of DOCUMENT, a use of LITERAL, and a parameterStyle of WRAPPED. WSDL style is a confusing topic that is critical for interoperability of Web Services across multiple platforms (e.

g., Java and .Net).

This topic is described in depth in 4, Section 4.3. Based on the style of WSDL being employed, JAX-WS de nes two beans for each method: a request bean and a response bean.

These beans are essentially wrappers for the request parameters and response value. When serialized by JAXB, the request bean and response bean produce the correct SOAP request message body and SOAP response message body, respectively..

2.3.16 XML Catalogs JAX-WS provides support for XML Catalogs including the OASIS XML Catalogs 1.1 speci cations. This is a great feature because, as discussed in 4, it s helpful for WSDL documents to import external schemas so that you don t have to keep duplicating the same schema information in each WSDL document whenever you use standard types.

The challenge to importing schemas is being able to nd them at runtime. Should you deploy the schemas on some local HTTP server You could, but if that URL ends up as http://localhost/myschema.xsd, it s not going to resolve properly on another machine.

An XML Catalog lets you map external references to imported schemas to local instances of such schemas. If you do your packaging properly (e.g.

, adding schemas to the application jar les), these local instances should be. 19. It also supports docume barcode code39 for Java nt/literal/bare, which is not WS-I-compliant. 20.

See Section 3.6.2.

3 of [JSR 224]. 21. See Section 3.

6.2.1 of [JSR 224].

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