Web Services Invocation Framework: Difference between revisions

Revision as of 23:48, 10 December 2014

Revision as of 15:00, 24 December 2014

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| name = Apache WSIF

| logo =

| screenshot =

| caption =

| developer = [[Apache Software Foundation]]

| latest_release_version = 2.0

| latest_release_date = January 27, 2003

| operating_system = [[Cross-platform]]

| genre = [[Web Servicesservices]]

| license = [[Apache License]] 2.0

| website = {{URL|http://ws.apache.org/wsif}}

}}

The '''Web Services Invocation Framework''' (WSIF) supports a simple [[Java (programming language)|Java]] API for invoking [[Web Servicesservices]], no matter how or where the services are provided. The framework allows maximum flexibility for the invocation of any [[Web Services Description Language|WSDL]] (WSDL)-described service.

Using WSIF, WSDL can become the centerpiece of an integration framework for accessing software running on diverse platforms and using widely varying protocols. The only precondition is that youthe needsoftware needs to describebe your softwaredescribed using WSDL, and includeto have included in its description a binding that yourthe client's WSIF framework has a provider for. WSIF defines and comes packaged with providers for local Java, [[EJBEnterprise JavaBeans]] (EJB), [[Java Message Service|JMS]] (JMS), and [[Java EE Connector Architecture|JCA]] (JCA) protocols., Thatwhich means youthat a client can define an [[Enterprise JavaBeans]]EJB or a [[Java Message Service]]-accessible service directly as a WSDL binding and access it transparently using WSIF, using the same API youone would use for a SOAP service or even a local Java class.

== WSIF Structure ==

In WSDL, a binding defines how to map between the abstract ''PortType'' and a real service format and protocol. For example, the SOAP binding defines the encoding style, the ''SOAPAction'' header, the namespace of the body (the targetURI), and so forth.

WSDL allows there to be multiple implementations for a Web Serviceservice, and multiple Portsports that share the same PortType. In other words, WSDL allows the same interface to have bindings to for example, SOAP and IIOP.

WSIF provides an API to allow the same client code to access any available binding. As the client code can then be written to the PortType, it can be a deployment or configuration setting (or a code choice) which port and binding it uses.

WSIF uses ''providers'' to support these multiple WSDL bindings. A provider is a piece of code that supports a WSDL extension and allows invocation of the service through that particular implementation. WSIF providers use the J2SE JAR service provider specification, making them discoverable at [[Run time (program lifecycle phase)|runtime]].

Clients can then utilize any new implementations and can delegate the choice of port to the infrastructure and runtime, which allows the implementation to be chosen on the basis of quality of service characteristics or business policy.

== WSDL bindingsBindings for EJBs, JMS, and JCA... ==

WSIF defines additional binding extensions so that [[Enterprise JavaBean|EJBs]] (EJBs), local Java classes, software accessible over [[message queue]]s using the [[Java Message Service|JMS]] (JMS) API and software that can be invoked using the [[Java EE Connector Architecture|Java Connector architecture]] can also be described in WSDL. WSIF is packaged with providers that allow transparent invocation of such software given the corresponding WSDL description.

== Description of WSIF ==

WSIF defines additional binding extensions so that [[Enterprise JavaBean|EJBs]], local Java classes, software accessible over [[message queue]]s using the [[Java Message Service|JMS]] API and software that can be invoked using the [[Java EE Connector Architecture|Java Connector architecture]] can also be described in WSDL. WSIF is packaged with providers that allow transparent invocation of such software given the corresponding WSDL description.

== Description of WSIF ==

WSIF enables developers to interact with abstract representations of Web services through their WSDL descriptions instead of working directly with the Simple Object Access Protocol (SOAP) APIs, which is the usual programming model. With WSIF, developers can work with the same programming model regardless of how the Web service is implemented and accessed.

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Finally, WSIF is closely based upon WSDL, so it can invoke any service that can be described in WSDL.

WhatIf does all this enable? Imagine youra complicated Enterpriseenterprise software system consistingconsists of various pieces of software, developed over a period of tens of years - EJBs, legacy apps accessed using Java's connector architecture, SOAP services hosted on external servers, old code accessed through messaging middleware. You– needit is necessary to write software applications that use all these pieces to do useful things;, yet the differences in protocols, mobility of software, etc. comesget in the way.

TheIf the software youone useuses moves to a different server, so yourthe code breaks. The SOAP libraries youone useuses change - say for example, youwhen movedone moves from using Apache SOAP to Apache Axis -– so your code breaks sincebecause it uses a now deprecated SOAP API. Something that was previously accessible as an EJB is now available through messaging middleware via JMS - again, you need to fix the code that uses the software., Oror let'sif suppose youone havehas an EJB which is offered as a SOAP service to external clients. Using SOAP obviously results in a performance penalty as compared to accessing the EJB directly. Of course, SOAP is a great baseline protocol for platform and language independence, but shouldn't java clients be able to take advantage of the fact that the software they are accessing is really an EJB? So your java customers pay a performance penalty since you have to use SOAP for to accommodate you non-java clients.

WSIF fixes these problems by lettingallowing youWSDL useto WSDLbe used as a normalized description of disparate software, and allows youone to access this software in a manner that is independent of protocol or ___location. So whether it is SOAP, an EJB, JMS (or potentially .NET and other software frameworks), youthere haveis an API centered around WSDL which youis useused to access the functionality., Thiswhich lets youone write code that adapts to changes easily. The separation of the API from the actual protocol also means youthere haveis flexibility - you can switch protocols, ___location, etc. without having to even recompile your client code. So if your an externally available SOAP service becomes available as an EJB, youone can switch to using RMI/IIOP by just changing the service description (the WSDL), without having to make any modification in applications that use the service. You can exploit WSDL's extensibility, its capability to offer multiple bindings for the same service, deciding on a binding at runtime, etc.

== Differences between WSIF and Axis ==

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Axis is an implementation of SOAP. It includes on the server-side infrastructure for deploying web service implementations and then routing SOAP messages between clients and those implementations. It also implements the JAX-RPC specification for invoking SOAP services.

WSIF is similar to the client piece of Axis, in that it is used for invoking services. However, WSIF's API is WSDL-driven and protocol independent; it allows protocol-specific code ("providers") to be plugged in. For invoking SOAP services, WSIF is in fact packaged with an Axis provider, that uses Axis APIs (i.e. JAX-RPC) to do the invocation. So WSIF operates at a more abstract level than Axis.

== Differences between WSIF and JAX-RPC ==

JAX-RPC is an API for invoking XML-based RPC services -– essentially its current scope is limited to invocation of SOAP services. WSIF is an API for invoking WSDL-described services, whether they happen to be SOAP services or not (for example, WSIF defines WSDL bindings so that EJBs, enterprise software accessible using JMS or the Java Connector architecture as well as local Java classes can all be described as first-class WSDL services and then invoked using the same, protocol-independent [[WSIF]] API).

== See also ==

* [[Apache Web Services]]

* [[Apache XML]]

== References==

{{Reflist}}

== External links ==

* [http://ws.apache.org/wsif/ Web Services Invocation Framework documentation]

* [http://publib.boulder.ibm.com/infocenter/ws51help/index.jsp?topic=/com.ibm.websphere.nd.doc/info/ae/ae/cwsf_wsdl.html WSIF and WSDL]

* [http://www.s-cube-network.eu/km/terms/s/service-binding Service Binding]