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。
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",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",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",className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHi") @WebMethod @ResponseWrapper(localName = "sayHiResponse",className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiResponse") public java.lang.String sayHi( @WebParam(name = "text",targetNamespace = "") java.lang.String text ); @RequestWrapper(localName = "sayHiToUser",className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUser") @ResponseWrapper(localName = "sayHiToUserResponse",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",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,targetNamespace = "") AsyncHandler<com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUserResponse> asyncHandler ); @WebResult(name = "return",targetNamespace = "") @RequestWrapper(localName = "sayHiToUser",className = "com.neareast.test.cxf.asyClient.WSDL2Java.SayHiToUser") @WebMethod @ResponseWrapper(localName = "sayHiToUserResponse",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",className = "com.neareast.test.cxf.asyClient.WSDL2Java.GetUsers") @ResponseWrapper(localName = "getUsersResponse",className = "com.neareast.test.cxf.asyClient.WSDL2Java.GetUsersResponse") @WebMethod(operationName = "getUsers") public Response<com.neareast.test.cxf.asyClient.WSDL2Java.GetUsersResponse> getUsersAsync(); @RequestWrapper(localName = "getUsers",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",className = "com.neareast.test.cxf.asyClient.WSDL2Java.GetUsers") @WebMethod @ResponseWrapper(localName = "getUsersResponse",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:
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(); }
-
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; @Override public 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。
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