CXF入门教程
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CXF入门教程(5) -- webService异步调用模式
除了教程(3)中介绍的常见的同步调用模式,CXF还支持如下两种形式的异步调用模式:
- 轮询方法(Polling approach) - 这种情况下调用远程方法,我们可以调用一个特殊的方法;该方法没有输出参数,但是返回一个 javax.xml.ws.Response 实例。可以轮询该 Response 对象(继承自 javax.util.concurrency.Future 接口)来检查是否有应答消息到达。
- 回调方法(Callback approach) -这种情况下调用远程方法,我们调用另外一个特殊的方法:该方法使用一个回调对象(javax.xml.ws.AsyncHandler类型)的引用作为一个参数。只要有应答消息到达客户端,CXF运行时就会回调该 AsyncHandler 对象,并将应答消息的内容传给它。
下面是两种异步调用的方法的描述和示例代码。
异步调用示例使用的契约
下面展示的是异步调用示例中使用的WSDL契约,为保证教程的连续性,本文使用的是前面教程(1)中生成的HelloWorld服务的WSDL契约。
<?xml version="1.0" ?><wsdl:definitions name="HelloWorld"targetNamespace="http://service.server.cxf.test.neareast.com/"xmlns:ns1="http://schemas.xmlsoap.org/soap/http" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"xmlns:tns="http://service.server.cxf.test.neareast.com/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"xmlns:xsd="http://www.w3.org/2001/XMLSchema"><wsdl:types><xs:schema attributeFormDefault="unqualified"elementFormDefault="unqualified" targetNamespace="http://service.server.cxf.test.neareast.com/"xmlns:tns="http://service.server.cxf.test.neareast.com/" xmlns:xs="http://www.w3.org/2001/XMLSchema"><xs:element name="IntegerUserMap" type="tns:IntegerUserMap"></xs:element><xs:complexType name="User"><xs:sequence><xs:element minOccurs="0" name="name" type="xs:string"></xs:element></xs:sequence></xs:complexType><xs:complexType name="IntegerUserMap"><xs:sequence><xs:element maxOccurs="unbounded" minOccurs="0" name="entry"type="tns:IdentifiedUser"></xs:element></xs:sequence></xs:complexType><xs:complexType name="IdentifiedUser"><xs:sequence><xs:element name="id" type="xs:int"></xs:element><xs:element minOccurs="0" name="user" type="tns:User"></xs:element></xs:sequence></xs:complexType><xs:element name="sayHi" type="tns:sayHi"></xs:element><xs:complexType name="sayHi"><xs:sequence><xs:element minOccurs="0" name="text" type="xs:string"></xs:element></xs:sequence></xs:complexType><xs:element name="sayHiResponse" type="tns:sayHiResponse"></xs:element><xs:complexType name="sayHiResponse"><xs:sequence><xs:element minOccurs="0" name="return" type="xs:string"></xs:element></xs:sequence></xs:complexType><xs:element name="sayHiToUser" type="tns:sayHiToUser"></xs:element><xs:complexType name="sayHiToUser"><xs:sequence><xs:element minOccurs="0" name="arg0" type="tns:User"></xs:element></xs:sequence></xs:complexType><xs:element name="sayHiToUserResponse" type="tns:sayHiToUserResponse"></xs:element><xs:complexType name="sayHiToUserResponse"><xs:sequence><xs:element minOccurs="0" name="return" type="xs:string"></xs:element></xs:sequence></xs:complexType><xs:element name="getUsers" type="tns:getUsers"></xs:element><xs:complexType name="getUsers"><xs:sequence></xs:sequence></xs:complexType><xs:element name="getUsersResponse" type="tns:getUsersResponse"></xs:element><xs:complexType name="getUsersResponse"><xs:sequence><xs:element minOccurs="0" name="return" type="tns:IntegerUserMap"></xs:element></xs:sequence></xs:complexType></xs:schema></wsdl:types><wsdl:message name="getUsers"><wsdl:part element="tns:getUsers" name="parameters"></wsdl:part></wsdl:message><wsdl:message name="sayHi"><wsdl:part element="tns:sayHi" name="parameters"></wsdl:part></wsdl:message><wsdl:message name="sayHiToUser"><wsdl:part element="tns:sayHiToUser" name="parameters"></wsdl:part></wsdl:message><wsdl:message name="sayHiToUserResponse"><wsdl:part element="tns:sayHiToUserResponse" name="parameters"></wsdl:part></wsdl:message><wsdl:message name="sayHiResponse"><wsdl:part element="tns:sayHiResponse" name="parameters"></wsdl:part></wsdl:message><wsdl:message name="getUsersResponse"><wsdl:part element="tns:getUsersResponse" name="parameters"></wsdl:part></wsdl:message><wsdl:portType name="iHelloWorld"><wsdl:operation name="sayHi"><wsdl:input message="tns:sayHi" name="sayHi"></wsdl:input><wsdl:output message="tns:sayHiResponse" name="sayHiResponse"></wsdl:output></wsdl:operation><wsdl:operation name="sayHiToUser"><wsdl:input message="tns:sayHiToUser" name="sayHiToUser"></wsdl:input><wsdl:output message="tns:sayHiToUserResponse" name="sayHiToUserResponse"></wsdl:output></wsdl:operation><wsdl:operation name="getUsers"><wsdl:input message="tns:getUsers" name="getUsers"></wsdl:input><wsdl:output message="tns:getUsersResponse" name="getUsersResponse"></wsdl:output></wsdl:operation></wsdl:portType><wsdl:binding name="HelloWorldSoapBinding" type="tns:iHelloWorld"><soap:binding style="document"transport="http://schemas.xmlsoap.org/soap/http"></soap:binding><wsdl:operation name="sayHi"><soap:operation soapAction="" style="document"></soap:operation><wsdl:input name="sayHi"><soap:body use="literal"></soap:body></wsdl:input><wsdl:output name="sayHiResponse"><soap:body use="literal"></soap:body></wsdl:output></wsdl:operation><wsdl:operation name="sayHiToUser"><soap:operation soapAction="" style="document"></soap:operation><wsdl:input name="sayHiToUser"><soap:body use="literal"></soap:body></wsdl:input><wsdl:output name="sayHiToUserResponse"><soap:body use="literal"></soap:body></wsdl:output></wsdl:operation><wsdl:operation name="getUsers"><soap:operation soapAction="" style="document"></soap:operation><wsdl:input name="getUsers"><soap:body use="literal"></soap:body></wsdl:input><wsdl:output name="getUsersResponse"><soap:body use="literal"></soap:body></wsdl:output></wsdl:operation></wsdl:binding><wsdl:service name="HelloWorld"><wsdl:port binding="tns:HelloWorldSoapBinding" name="HelloWorldImplPort"><soap:address location="http://localhost:9000/helloWorld"></soap:address></wsdl:port></wsdl:service></wsdl:definitions>
生成异步 stub 代码
异步调用需要额外的stub代码(例如,服务端点接口中定义的专用的异步方法)。然而,这些特殊的stub代码不是默认生成的。要想打开异步特性,并生成必不可少的stub代码,我们必须使用WSDL 2.0规范的自定义映射特性。
自定义使我们能够改变 wsdl2java 工具生成stub代码的方式。特别地,它允许我们修改WSDL到Java的映射,并打开某些特性。在这里,自定义的作用是打开异步调用特性。自定义是用一个绑定声明规定的,该声明是我们用一个 jaxws:bindings 标签(jaxws 前缀绑定到 http://java.sun.com/xml/ns/jaxws 命名空间)定义的。指定一个绑定声明有两种可选的方式:
- 外部绑定声明 - jaxws:bindings 元素被定义在WSDL契约之外的一个单独的文件。生成stub代码的时候,我们需要对wsdl2java 工具指定绑定声明文件的位置。
- 嵌入式绑定声明 - 我们也可以直接把jaxws:bindings 元素嵌入到 WSDL 契约中,把它当做WSDL的扩展。在这种情况下,jaxws:bindings 的设置仅对直接的父元素起作用。
本文只考虑第一种方法,即外部绑定声明。一个打开了异步调用开关的绑定声明文件的模版如下所示:
<bindings xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" wsdlLocation="http://localhost:9000/helloWorld?wsdl" xmlns="http://java.sun.com/xml/ns/jaxws"> <bindings node="wsdl:definitions"> <enableAsyncMapping>true</enableAsyncMapping> </bindings></bindings>
其中的wsdlLocation指定了该绑定声明影响的WSDL文件的位置,可以是本地文件或一个URL。node节点是一个XPath 值,指定该绑定声明影响所影响的WSDL契约中的节点。 此处把node设为“wsdl:definitions”,表示我们希望对整个WSDL契约起作用。{jaxws:enableAsyncMapping}} 元素设置为true,用来使能异步调用特性。
如果我们只想对一个端口“iHelloWorld”生成异步方法,我们可以在前面的绑定声明中指定<bindings node="wsdl:definitions/wsdl:portType[@name='iHelloWorld']"> 。
接下来我们就可以使用wsdl2java命令来生成相应的带异步支持的stub代码了。为简单起见,假设绑定声明文件存储在本地文件async_binding.xml中,我们可以使用类似下面的命令:
wsdl2java -b async_binding.xml hello_world.wsdl
其中-b 选项用来指定绑定声明文件。通过这种方法生成stub代码之后,HelloWorld的服务端点接口定义如下:
import java.util.concurrent.Future;import javax.jws.WebMethod;import javax.jws.WebParam;import javax.jws.WebResult;import javax.jws.WebService;import javax.xml.bind.annotation.XmlSeeAlso;import javax.xml.ws.AsyncHandler;import javax.xml.ws.RequestWrapper;import javax.xml.ws.Response;import javax.xml.ws.ResponseWrapper;@WebService(targetNamespace = "http://service.server.cxf.test.neareast.com/", name = "iHelloWorld")@XmlSeeAlso({ObjectFactory.class})public interface IHelloWorld { @RequestWrapper(localName = "sayHi", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHi") @ResponseWrapper(localName = "sayHiResponse", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiResponse") @WebMethod(operationName = "sayHi") public Response<com.neareast.test.cxf.asyClient.WSDL2Java.SayHiResponse> sayHiAsync( @WebParam(name = "text", targetNamespace = "") java.lang.String text ); @RequestWrapper(localName = "sayHi", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHi") @ResponseWrapper(localName = "sayHiResponse", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiResponse") @WebMethod(operationName = "sayHi") public Future<?> sayHiAsync( @WebParam(name = "text", targetNamespace = "") java.lang.String text, @WebParam(name = "asyncHandler", targetNamespace = "") AsyncHandler<com.neareast.test.cxf.asyClient.WSDL2Java.SayHiResponse> asyncHandler ); @WebResult(name = "return", targetNamespace = "") @RequestWrapper(localName = "sayHi", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHi") @WebMethod @ResponseWrapper(localName = "sayHiResponse", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiResponse") public java.lang.String sayHi( @WebParam(name = "text", targetNamespace = "") java.lang.String text ); @RequestWrapper(localName = "sayHiToUser", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUser") @ResponseWrapper(localName = "sayHiToUserResponse", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUserResponse") @WebMethod(operationName = "sayHiToUser") public Response<com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUserResponse> sayHiToUserAsync( @WebParam(name = "arg0", targetNamespace = "") com.neareast.test.cxf.asyClient.WSDL2Java.User arg0 ); @RequestWrapper(localName = "sayHiToUser", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUser") @ResponseWrapper(localName = "sayHiToUserResponse", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUserResponse") @WebMethod(operationName = "sayHiToUser") public Future<?> sayHiToUserAsync( @WebParam(name = "arg0", targetNamespace = "") com.neareast.test.cxf.asyClient.WSDL2Java.User arg0, @WebParam(name = "asyncHandler", targetNamespace = "") AsyncHandler<com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUserResponse> asyncHandler ); @WebResult(name = "return", targetNamespace = "") @RequestWrapper(localName = "sayHiToUser", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUser") @WebMethod @ResponseWrapper(localName = "sayHiToUserResponse", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUserResponse") public java.lang.String sayHiToUser( @WebParam(name = "arg0", targetNamespace = "") com.neareast.test.cxf.asyClient.WSDL2Java.User arg0 ); @RequestWrapper(localName = "getUsers", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.GetUsers") @ResponseWrapper(localName = "getUsersResponse", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.GetUsersResponse") @WebMethod(operationName = "getUsers") public Response<com.neareast.test.cxf.asyClient.WSDL2Java.GetUsersResponse> getUsersAsync(); @RequestWrapper(localName = "getUsers", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.GetUsers") @ResponseWrapper(localName = "getUsersResponse", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.GetUsersResponse") @WebMethod(operationName = "getUsers") public Future<?> getUsersAsync( @WebParam(name = "asyncHandler", targetNamespace = "") AsyncHandler<com.neareast.test.cxf.asyClient.WSDL2Java.GetUsersResponse> asyncHandler ); @WebResult(name = "return", targetNamespace = "") @RequestWrapper(localName = "getUsers", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.GetUsers") @WebMethod @ResponseWrapper(localName = "getUsersResponse", targetNamespace = "http://service.server.cxf.test.neareast.com/", className = "com.neareast.test.cxf.asyClient.WSDL2Java.GetUsersResponse") public com.neareast.test.cxf.asyClient.WSDL2Java.IntegerUserMap getUsers();}
除了原来的同步方法(如sayHi方法),sayHi操作的两个异步调用方法也被同时生成了:
- 返回值类型为Future<?>,有一个类型为javax.xml.ws.AsyncHandler的额外参数的sayHiAsync()方法 —— 该方法可用于异步调用的回调方式。
- 返回值类型为Response<GreetMeSometimeResponse>的sayHiAsync()方法 —— 该方法可用于异步调用的轮询方式。
回调方式和轮询方式的细节将在下面的章节讨论。为体现异步调用的特点,笔者修改了教程(1)中Helloworld服务的部分实现,在sayHiToUser()方法中加入了3秒钟的休眠,并增强了代码的鲁棒性,改动如下:
public String sayHiToUser(User user) {String retVal = null;if(null == user){retVal = "Error: user object null !";}else{try{System.out.println("sleep for 3 seconds before return");Thread.sleep(3000);}catch(InterruptedException e){e.printStackTrace();}System.out.println("sayHiToUser called by: " + user.getName());users.put(users.size() + 1, user);retVal = "Hello " + user.getName();}return retVal;}
实现一个轮询方式的异步调用客户端
下面的代码演示了异步发送操作调用的轮询方式的实现。客户端是通过特殊的Java方法 _OperationName_Async(本例为sayHiAsync()方法)来调用这个操作的,该方法返回一个javax.xml.ws.Response<T> 对象,其中“T”是这个操作的响应消息的类型(本例中为SayHiResponse类型)。我们可以稍后通过轮询Response<T> 对象来检查该操作的响应消息是否已经到达。
package com.neareast.test.cxf.asyClient.consumer;import java.util.concurrent.ExecutionException;import javax.xml.ws.Response;import com.neareast.test.cxf.asyClient.WSDL2Java.HelloWorld;import com.neareast.test.cxf.asyClient.WSDL2Java.IHelloWorld;import com.neareast.test.cxf.asyClient.WSDL2Java.SayHiResponse;public class BasicClientPolling {public static void main(String[] args) throws InterruptedException{HelloWorld server = new HelloWorld();IHelloWorld hello = server.getHelloWorldImplPort();Response<SayHiResponse> sayHiResponseResp = hello.sayHiAsync(System.getProperty("user.name"));while (!sayHiResponseResp.isDone()) {Thread.sleep(100);}try {SayHiResponse reply = sayHiResponseResp.get();System.out.println( reply.getReturn() );} catch (ExecutionException e) {e.printStackTrace();}}}
sayHiAsync()方法调用了sayHi操作,将输入参数传送到远程的服务,并返回javax.xml.ws.Response<SayHiResponse> 对象的一个引用。Response 类实现了标准的 java.util.concurrency.Future<T> 接口,该类设计用来轮询一个并发线程执行的任务的产出结果。本质上来说,使用Response对象来轮询有两种基本方法:
- Non-blocking polling(非阻塞轮询) - 尝试获得结果之前,调用非阻塞方法Response<T>.isDone()来检查响应消息是否到达,例如:
<pre name="code" class="java">User u = new User();//非阻塞式轮询u.setName(System.getProperty("user.name"));Response<SayHiToUserResponse> sayHiToUserResponseResp = hello.sayHiToUserAsync(u);while (!sayHiToUserResponseResp.isDone()) {Thread.sleep(100);}try {//如果没有前面isDone的检测,此处就退化为阻塞式轮询SayHiToUserResponse reply = sayHiToUserResponseResp.get();System.out.println( reply.getReturn() );} catch (ExecutionException e) {e.printStackTrace();}</pre><br><pre></pre><pre></pre><pre></pre><pre></pre><pre></pre><pre></pre><pre></pre>
- Blocking polling(阻塞轮询) - 立即调用Response<T>.get(),阻塞至响应到达(可以指定一个超时时长作为可选项)。例如,轮询一个响应,超时时长为60s:
//阻塞式轮询u.setName("NearEast");sayHiToUserResponseResp = hello.sayHiToUserAsync(u);try {SayHiToUserResponse reply = sayHiToUserResponseResp.get(5L,java.util.concurrent.TimeUnit.SECONDS);System.out.println( reply.getReturn() );} catch (ExecutionException e) {e.printStackTrace();} catch (TimeoutException e) {e.printStackTrace();}
实现一个回调方式的异步调用客户端
发起异步操作调用的另一个可选方法是实现javax.xml.ws.AsyncHandler接口,派生出一个回调类。回调类必须实现 handleResponse() 方法,CXF运行时调用这个类将响应的到达通知给客户端。下面的代码给出了我们需要实现的 AsyncHandler 接口的轮廓。
package javax.xml.ws;public interface AsyncHandler<T>{ void handleResponse(Response<T> res);}
本例使用一个测试用的回调类 SayHiToUserAsyHandler,代码如下:
package com.neareast.test.cxf.asyClient.consumer;import java.util.concurrent.ExecutionException;import javax.xml.ws.AsyncHandler;import javax.xml.ws.Response;import com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUserResponse;public class SayHiToUserAsyHandler implements AsyncHandler<SayHiToUserResponse> {SayHiToUserResponse reply = null;@Overridepublic void handleResponse(Response<SayHiToUserResponse> res) {try {reply = res.get();System.out.println( reply.getReturn() );} catch (ExecutionException e) {e.printStackTrace();} catch (InterruptedException e) {e.printStackTrace();}}public String getResponseText(){return reply.getReturn();}}
上述 handleResponse() 的实现只是简单地获取响应数据,并把它存放到成员变量reply中。额外的getResponseText() 方法是为了方便地从响应中提炼出主要的输出参数。
下面的代码演示了发起异步操作调用的回调方法。客户端通过特定的Java方法 _OperationName_Async()来调用相应的操作,该方法使用一个额外的AsyncHandler<T>类型的参数,并返回一个 java.util.concurrency.Future<?> 对象。
package com.neareast.test.cxf.asyClient.consumer;import java.util.concurrent.Future;import com.neareast.test.cxf.asyClient.WSDL2Java.HelloWorld;import com.neareast.test.cxf.asyClient.WSDL2Java.IHelloWorld;import com.neareast.test.cxf.asyClient.WSDL2Java.User;public class BasicCallbackClient {public static void main(String[] args) throws InterruptedException{HelloWorld server = new HelloWorld();IHelloWorld hello = server.getHelloWorldImplPort();User u = new User();//非阻塞式轮询u.setName(System.getProperty("user.name"));SayHiToUserAsyHandler asyHandler = new SayHiToUserAsyHandler();Future<?> res = hello.sayHiToUserAsync(u, asyHandler);while (!res.isDone()) {Thread.sleep(100);}String reply = asyHandler.getResponseText();System.out.println( reply );}}
sayHiToUserAsync()方法返回的 Future<?> 对象只是用来检测一个响应是否已经到达的 —— 例如,通过调用response.isDone()来轮询。响应消息的值只在回调对象SayHiToUserAsyHandler 中可得。
本文配套的完整代码已经上传,包括用到的wsdl契约文件和绑定声明文件;本文涉及的异步调用客户端的代码放在com.neareast.test.cxf.asyClient包下,欢迎下载:http://download.csdn.net/detail/neareast/4421250。
本文参考自:http://cxf.apache.org/docs/developing-a-consumer.html
转载自NearEast
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