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| <title>Apache Axis2 User's Guide- Introduction to Services</title> | |
| </head> | |
| <body> | |
| <a name="introservices" id="introservices"></a> | |
| <h1>Apache Axis2 User's Guide - Introduction to Services</h1> | |
| <p>The term "Web services" can apply to a number of different ways | |
| of sending information back and forth. However, this guide focuses | |
| on the sending and receiving of SOAP messages. SOAP messages are | |
| XML documents that consist of an "envelope" containing a "payload" | |
| (see Code Listing 4).</p> | |
| <h2>Content</h2> | |
| <ul> | |
| <li><a href="userguide.html#intro">Introducing Axis2</a><br /> | |
| <ul> | |
| <li><a href="userguide.html#whatis">What is Axis2?</a></li> | |
| <li><a href="userguide.html#underhood">What's under the | |
| hood?</a></li> | |
| <li><a href="userguide.html#handlessoap">How Axis2 handles SOAP | |
| messages</a></li> | |
| <li><a href="userguide.html#distributions">Axis2 | |
| distributions</a></li> | |
| <li><a href="userguide.html#sbd">The Axis2 Standard Binary | |
| Distribution</a></li> | |
| <li><a href="userguide.html#hierarchy">Axis2.war Directory | |
| Hierarchy</a></li> | |
| <li><a href="userguide.html#docs">Axis2 Documents | |
| Distribution</a></li> | |
| <li><a href="userguide.html#clients">Axis2 and clients</a></li> | |
| </ul> | |
| </li> | |
| <li><a href= | |
| "userguide-installingtesting.html#installingtesting">Installing and | |
| testing client code</a></li> | |
| <li><a href= | |
| "userguide-introtoservices.html#introservices"><strong>Introduction | |
| to Services</strong></a><br /> | |
| <ul> | |
| <li><a href= | |
| "userguide-introtoservices.html#messageexchange"><strong>Message | |
| Exchange Patterns</strong></a></li> | |
| </ul> | |
| </li> | |
| <li><a href="userguide-creatingclients.html#createclients">Creating | |
| Clients</a><br /> | |
| <ul> | |
| <li><a href= | |
| "userguide-creatingclients.html#choosingclient">Choosing a Client | |
| Generation Method</a></li> | |
| <li><a href="userguide-creatingclients.html#generating">Generating | |
| Clients</a></li> | |
| <li><a href="userguide-creatingclients.html#adb">Axis Data Binding | |
| (ADB)</a></li> | |
| </ul> | |
| </li> | |
| <li><a href= | |
| "userguide-buildingservices.html#buildservices">Building | |
| Services</a><br /> | |
| <ul> | |
| <li><a href= | |
| "userguide-buildingservices.html#getcomfortable">Getting | |
| Comfortable with the Available Options</a></li> | |
| <li><a href= | |
| "userguide-buildingservices.html#createscratch">Creating a service | |
| from scratch</a></li> | |
| <li><a href="userguide-buildingservices.html#deploypojo">Deploying | |
| Plain Old Java Objects</a></li> | |
| <li><a href="userguide-buildingservices.html#deployrun">Deploying | |
| and running an Axis2 service created from WSDL</a></li> | |
| </ul> | |
| </li> | |
| <li><a href="userguide-samples.html">Samples</a></li> | |
| <li><a href="userguide-forfurtherstudy.html">For Further | |
| Study</a></li> | |
| </ul> | |
| <h3>Code Listing 4: Example SOAP Message</h3> | |
| <pre> | |
| <?xml version='1.0' ?> | |
| <env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope" | |
| xmlns:wsa="http://www.w3.org/2005/03/addressing"> | |
| <env:Header> | |
| <wsa:MessageID> | |
| http://ws.apache.org/9C21DE32-DB42-1228-C42E-66CB101421AD | |
| </wsa:MessageID> | |
| <wsa:ReplyTo> | |
| <wsa:Address>http://example.com/projects/clientApp</wsa:Address> | |
| </wsa:ReplyTo> | |
| <wsa:To>http://example.com/axis2/publishingService</wsa:To> | |
| <wsa:Action>http://example.com/axis2/addDocument</wsa:Action> | |
| </env:Header> | |
| <env:Body> | |
| <addDocument> | |
| <docTitle>What I Did On My Summer Vacation</doctitle> | |
| <docSubtitle>Children's Essays from Accross the World</docSubtitle> | |
| <docLocation>contentRepos/summerVac.doc</docLocation> | |
| </addDocument> | |
| </env:Body> | |
| </env:Envelope> | |
| </pre> | |
| <p>This XML document consists of the outer element or the SOAP | |
| Envelope, and its contents. The SOAP Envelope is in the SOAP | |
| namespace, http://www.w3.org/2003/05/soap-envelope, prefixed as | |
| env: and contains up to two children. This envelope is a standard | |
| format that pertains to every single SOAP message sent and received | |
| by any SOAP Web service.</p> | |
| <p>The contents of the Envelope consists of two parts; the first | |
| being the SOAP headers-the contents of the env:Header element. | |
| These headers, such as the WS-Addressing elements shown here, | |
| provide additional information about the message and how it should | |
| be handled. A SOAP message may carry headers relating to several | |
| aspects of the message, or it may carry no headers at all. These | |
| headers are typically processed by the message handlers.</p> | |
| <p>The second and arguably the most important part of the message | |
| is the payload, which consists of the contents of the env:Body | |
| element. This is the actual message intended for the receiver, and | |
| it is the information that the main application will ultimately | |
| process.</p> | |
| <a name="messageexchange" id="messageexchange"></a> | |
| <h2>Message Exchange Patterns</h2> | |
| <p>Although all SOAP messages carry the same structure, the ways in | |
| which they are used can be combined into a number of different | |
| "message exchange patterns", or MEPs. The two major message | |
| exchange patterns are:</p> | |
| <ul> | |
| <li>In-Out: in this MEP, the client sends a SOAP message to the | |
| server, which processes the message and sends a response back. This | |
| is probably the most commonly used MEP, and is useful for tasks | |
| such as searching for information or submitting information in | |
| situations in where acknowledgment is important.</li> | |
| <li>In-Only: In this MEP, the client sends a message to the server | |
| without expecting a response. You may use this MEP for activities | |
| such as pinging a server to wake it up, reporting logging | |
| information for which you do not need an acknowledgment and so | |
| on.</li> | |
| </ul> | |
| <p>Within these two MEPs, you also have several variables to | |
| consider:</p> | |
| <ul> | |
| <li>Blocking versus non-blocking: When the client sends a message, | |
| the application may wait to receive a response before moving on, or | |
| it may simply send a message and move on by specifying a callback | |
| action to be completed when the response is received.</li> | |
| <li>Number of parameters: Ultimately, a message sent from a client | |
| to server is intended to execute a particular action. That action | |
| may not require any parameters, or it may require one or more | |
| parameters. These parameters must be encoded as part of the payload | |
| of the message.</li> | |
| </ul> | |
| <p>Taking all these options into consideration, you can create | |
| virtually any MEP. For example, you can create an Out-Only system | |
| by reversing roles for the In-Only MEP. Apache Axis2 also includes | |
| support for less prominent MEPs, such as Robust-In-Only.</p> | |
| <p><strong>See Next Section</strong> - <a href= | |
| "userguide-creatingclients.html#createclients">Creating | |
| Clients</a></p> | |
| </body> | |
| </html> |