3.motan之异步调用
一、什么是异步调用？
1.同步调用
方法间的调用，假设A方法调用B方法，A方法等待B方法执行完毕后才执行本身，这个同步调用，是具有阻塞式的调用，如果B方法非常耗时，那么整个方法的执行效率将会非常低；
2.异步调用
同样是方法间的调用，假设A方法调用B方法，不同的是A方法调用B方法后，B方法很快的返回给A方法个答复(这个答复不是执行完整个B方法的答复)，A方法收到答复后就执行本身，这个是异步调用，不管B方法是否耗时，整体的效率都提升。
二、motan的异步调用入门
1.首先，以入门案例为基础案例改造：http://www.cnblogs.com/Json1208/p/8784906.html
2.motan-api工程HelloWorldService添加注解@MotanAsync
package com.motan.service; import com.weibo.api.motan.transport.async.MotanAsync; @MotanAsync public interface HelloWorldService { String hello(String name); }
3.motan-api添加maven插件build-helper-maven-plugin，用来把自动生成类的目录设置为source path
<build> <plugins> <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>build-helper-maven-plugin</artifactId> <version>1.10</version> <executions> <execution> <phase>generate-sources</phase> <goals> <goal>add-source</goal> </goals> <configuration> <sources> <source>${project.build.directory}/generated-sources/annotations</source> </sources> </configuration> </execution> </executions> </plugin> </plugins> </build>
编译时，Motan自动生成异步service类，生成路径为target/generated-sources/annotations/，生成的类名为service名加上Async，例如service类名为HelloWorldService.java,则自动生成的类名为HelloWorldServiceAsync.java。
另外，需要将motan自动生产类文件的路径配置为项目source path，可以使用maven plugin或手动配置，以上使用maven plugin方式。
这样，我们就能在eclipse中的source folder 中生成HelloWorldServiceAsync.java。
4.motan-client.xml配置的motan:referer标签中配置interface为自动生成的以Async为后缀的对应service类
<motan:referer id="helloWorldReferer" interface="com.motan.service.HelloWorldServiceAsync" directUrl="localhost:8002"/>
5.测试，先启动server，再启动client
public class Server { @SuppressWarnings({ "unused", "resource" }) public static void main(String[] args) { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:motan-server.xml"); System.out.println("server start..."); } } log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. server start...
public class Client { @SuppressWarnings("resource") public static void main(String[] args) throws InterruptedException { ApplicationContext ctx = new ClassPathXmlApplicationContext(new String[]{"classpath:motan-client.xml"}); HelloWorldServiceAsync async = (HelloWorldServiceAsync) ctx.getBean("helloWorldReferer"); System.out.println(async.hello("motan")); } } log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. Hello motan!
最后再来看server的控制台，如果成功调用，会输出方法结果：
log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. server start... motan
三、motan异步调用详解
1.使用ResponseFuture接口来接收远程调用结果，ResponseFuture具备future和callback能力
①.将接口实现修改为：
package com.motan.service; public class HelloWorldServiceImpl implements HelloWorldService{ @Override public String hello(String name) { try { Thread.sleep(5000);
System.out.println(name); System.out.println("等待5s后返回"); } catch (InterruptedException e) { e.printStackTrace(); } return "Hello " + name + "!"; } }
②.修改客户端调用为：
package com.motan.client; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.motan.service.HelloWorldServiceAsync; import com.weibo.api.motan.rpc.ResponseFuture; public class Client { @SuppressWarnings("resource") public static void main(String[] args) throws InterruptedException { ApplicationContext ctx = new ClassPathXmlApplicationContext(new String[]{"classpath:motan-client.xml"}); HelloWorldServiceAsync async = (HelloWorldServiceAsync) ctx.getBean("helloWorldReferer"); ResponseFuture future = async.helloAsync("ResponseFuture"); System.out.println(future.getValue()); } }
注意：为了防止接口调用超时，消费端需要配置调用超时时间，在motan-client.xml中配置：
<motan:referer id="helloWorldReferer" interface="com.motan.service.HelloWorldServiceAsync" directUrl="localhost:8002" connectTimeout="8000" requestTimeout="8000"/>
③.启动服务端
log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. server start...
④.启动客户端
等待5s后服务端控制台打印：
log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. server start... ResponseFuture 等待5s后返回
客户端控制台打印：
log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. Hello ResponseFuture!
2.使用FutureListener监听，该监听器可以监听到接口是否成功调用，可以很灵活的判断如果成功调用在输出相关调用返回信息
虽然ResponseFuture带有isDone和isSuccess，但是经过测试，isDone和isSuccess并没办法在异步调用后用于判断，而是得配合FutureListener一起使用：
①.service实现不变，仍然是带有休眠的效果：
package com.motan.service; public class HelloWorldServiceImpl implements HelloWorldService{ @Override public String hello(String name) { try { Thread.sleep(5000); System.out.println(name); System.out.println("等待5s后返回"); } catch (InterruptedException e) { e.printStackTrace(); } return "Hello " + name + "!"; } }
②.使用FutureListener监听server端是否执行成功
package com.motan.client; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.motan.service.HelloWorldServiceAsync; import com.weibo.api.motan.rpc.Future; import com.weibo.api.motan.rpc.FutureListener; import com.weibo.api.motan.rpc.ResponseFuture; public class Client { @SuppressWarnings("resource") public static void main(String[] args) throws InterruptedException { ApplicationContext ctx = new ClassPathXmlApplicationContext(new String[]{"classpath:motan-client.xml"}); HelloWorldServiceAsync async = (HelloWorldServiceAsync) ctx.getBean("helloWorldReferer"); FutureListener listener = new FutureListener() { @Override public void operationComplete(Future future) throws Exception { System.out.println("async call " + (future.isSuccess() ? "sucess! value:" + future.getValue() : "fail! exception:" + future.getException().getMessage())); } }; ResponseFuture future1 = async.helloAsync("motan FutureListener..."); future1.addListener(listener); } }
③.测试
首先，执行server端启动程序：
package com.motan.server; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Server { @SuppressWarnings({ "unused", "resource" }) public static void main(String[] args) { ApplicationContext applicationContext = new ClassPathXmlApplicationContext("classpath:motan-server.xml"); System.out.println("server start..."); } } log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. server start...
接着，启动client端启动程序：
等待5s之后，server控制台输出：
log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. server start... motan FutureListener... 等待5s后返回
再来看client控制台输出：
log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. async call sucess! value:Hello motan FutureListener...!
注意：在server端休眠的时候，client端是阻塞着的，由于我们超时时间跟上方一致配置的是8s，所以并不会超时，导致client一致阻塞，我们试着把超时实际调为3s(比server休眠时间短)：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:motan="http://api.weibo.com/schema/motan" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://api.weibo.com/schema/motan http://api.weibo.com/schema/motan.xsd"> <!-- 具体referer配置。使用方通过beanid使用服务接口类 --> <motan:referer id="helloWorldReferer" interface="com.motan.service.HelloWorldServiceAsync" directUrl="localhost:8002" connectTimeout="3000" requestTimeout="3000"/> </beans>
重新启动server应用程序，server控制台输出：
log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. server start...
还未到休眠5s执行结束，client端就抛出一个异常：
log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. async call fail! exception:error_message: com.weibo.api.motan.rpc.DefaultResponseFuture task cancel: serverPort=localhost:8002 requestId=1597643022347010049
interface=com.motan.service.HelloWorldService method=hello(java.lang.String) cost=3042, status: 503, error_code: 10001,r=null
最后，server端才把休眠之后的消息打印：
log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment). log4j:WARN Please initialize the log4j system properly. server start... motan FutureListener... 等待5s后返回
说明：client使用监听器监听server是否执行完毕，若server实际执行业务的时间在client端配置的接口请求超时时间之内，那么client请求后会一致阻塞着，直到server实际业务执行完成返回；
若server实际执行业务的时间大于client端配置的接口请求超时时间，那么一旦到达超时时间，直接抛出异常。
