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| <h1>RESTful Web Services Support</h1> |
| |
| <p>This document presents an introduction on REST and REST with HTTP POST & |
| GET.</p> |
| |
| <h2>Content</h2> |
| <ul> |
| <li><a href="#intro">Introduction</a></li> |
| <li><a href="#rest_with_post">Doing REST Web Services with HTTP POST</a> |
| <ul> |
| <li><a href="#sample">Sample REST - HTTP POST Client</a></li> |
| </ul> |
| </li> |
| <li><a href="#rest_with_get">Access a REST Web Service via HTTP GET</a></li> |
| </ul> |
| |
| <a name="intro"></a> |
| <h2>Introduction</h2> |
| |
| <p>WSDL 2.0 HTTP Binding defines a way to implement REST (Representational State Transfer) with Web services. Axis2 implements most defined in HTTP binding specification. REST Web services are a reduced subset of the usual Web service stack.</p> |
| |
| <p>The Axis2 REST implementation assumes the following properties:</p> |
| <ol> |
| <li>REST Web services are Synchronous and Request Response in nature.</li> |
| <li>When REST Web services are accessed via GET, the service and the |
| operations are identified based on the URL. The parameters are assumed as |
| parameters of the Web service. In this case the GET based REST Web |
| services supports only simple types as arguments and it should adhere to <a href="http://www.w3.org/TR/2006/CR-wsdl20-adjuncts-20060327/#_operation_iri_style">IRI style</a>.</li> |
| <li>POST based Web services do not need a SOAP Envelope or a SOAP Body. |
| REST Web Services do not have Headers and the payload is sent |
| directly.</li> |
| </ol> |
| |
| <p>Axis2 can be configured as a REST Container and can be used to send and |
| receive RESTful Web service requests and responses. REST Web services can be |
| accessed using HTTP GET and POST.</p> |
| |
| <a name="rest_with_post"></a> |
| <h2>Doing REST Web Services with HTTP POST</h2> |
| |
| <p>Axis2 server, if REST is enabled, will act as both a REST endpoint and a SOAP endpoint. When a message is received, if the content type is text/xml and if the SOAPAction Header |
| is missing, then the message is treated as a RESTful Message, if not it is |
| treated as a usual SOAP Message.</p> |
| |
| <p>On sending a message, the fact that the message is RESTful or not, can |
| be decided from the client API.<br> |
| Set a property in the client api.<br> |
| </p> |
| <pre>... |
| Options options = new Options(); |
| options.setProperty(Constants.Configuration.ENABLE_REST, Constants.VALUE_TRUE); |
| ...</pre> |
| |
| <a name="sample"></a> |
| <h3>Sample REST - HTTP POST Client</h3> |
| |
| <p>There is an example named, userguide.clients.RESTClient.java which |
| demonstrates the usage of the above, using the "echo"operation of the</p> |
| <pre>userguide.example1.MyService </pre> |
| |
| <p>of the samples.The class source will be as follows:</p> |
| <source><pre>public class RESTClient { |
| |
| private static String toEpr = "http://localhost:8080/axis2/services/MyService"; |
| |
| public static void main(String[] args) throws AxisFault { |
| |
| Options options = new Options(); |
| options.setTo(new EndpointReference(toEpr)); |
| |
| options.setProperty(Constants.Configuration.ENABLE_REST, Constants.VALUE_TRUE); |
| |
| ServiceClient sender = new ServiceClient(); |
| sender.engageModule(new QName(Constants.MODULE_ADDRESSING)); |
| sender.setOptions(options); |
| OMElement result = sender.sendReceive(getPayload()); |
| |
| try { |
| XMLStreamWriter writer = XMLOutputFactory.newInstance() |
| .createXMLStreamWriter(System.out); |
| result.serialize(writer); |
| writer.flush(); |
| } catch (XMLStreamException e) { |
| e.printStackTrace(); |
| } catch (FactoryConfigurationError e) { |
| e.printStackTrace(); |
| } |
| } |
| private static OMElement getPayload() { |
| OMFactory fac = OMAbstractFactory.getOMFactory(); |
| OMNamespace omNs = fac.createOMNamespace( |
| "http://example1.org/example1", "example1"); |
| OMElement method = fac.createOMElement("echo", omNs); |
| OMElement value = fac.createOMElement("Text", omNs); |
| value.addChild(fac.createOMText(value, "Axis2 Echo String ")); |
| method.addChild(value); |
| |
| return method; |
| } |
| }</pre> |
| </source> |
| |
| <a name="rest_with_get"></a> |
| <h2>Access a REST Web Service via HTTP GET</h2> |
| |
| <p>Axis2 allows users to access Web services that have simple type parameters |
| via HTTP GET. For example, the following URL requests the Version Service via |
| HTTP GET. But the Web service arriving via GET assumes REST. Other parameters |
| are converted into XML and put into the SOAP Body.</p> |
| <source><pre>http://127.0.0.1:8080/axis2/rest/version/getVersion</pre> |
| </source> |
| <p>Result can be shown in the browser as follows:</p> |
| <img src="images/userguide/http-get-ws.jpg"/><br clear="all"/> |
| |
| <p>For example, the following request,</p> |
| <source><pre>http://127.0.0.1:8080/axis2/rest/version/getVersion</pre> |
| </source>will be converted to the following SOAP Message for processing by |
| Axis2.<source> |
| <pre> |
| <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"> |
| <soapenv:Body> |
| <axis2:getVersion xmlns:axis2="http://ws.apache.org/goGetWithREST" /> |
| </soapenv:Body> |
| </soapenv:Envelope> |
| </pre> |
| </source> |
| |
| <h2>Resources</h2> |
| |
| <p>How I Explained REST to My Wife, By Ryan Tomayko- <a |
| href="http://naeblis.cx/articles/2004/12/12/rest-to-my-wife">http://naeblis.cx/articles/2004/12/12/rest-to-my-wife</a></p> |
| |
| <p>Building Web Services the REST Way, By Roger L. Costello- <a |
| href="http://www.xfront.com/REST-Web-Services.html"> |
| http://www.xfront.com/REST-Web-Services.html</a></p> |
| |
| <p>Resource-oriented vs. activity-oriented Web services, By James Snell- <a |
| href="http://www-128.ibm.com/developerworks/webservices/library/ws-restvsoap/">http://www-128.ibm.com/developerworks/webservices/library/ws-restvsoap/</a></p> |
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