Hessian实现Webservice

Hessian是一个轻量级的remoting on http工具,采用的是Binary RPC协议，所以它很适合于发送二进制数据,同时又具有防火墙穿透能力。Hessian一般是通过Web应用来提供服务，因此非常类似于平时我们用的WebService。只是它不使用SOAP协议,但相比webservice而言更简单、快捷。

Hessian官网：http://hessian.caucho.com/

Hessian可通过Servlet提供远程服务，需要将匹配某个模式的请求映射到Hessian服务。也可Spring框架整合，通过它的DispatcherServlet可以完成该功能，DispatcherServlet可将匹配模式的请求转发到Hessian服务。Hessian的server端提供一个servlet基类, 用来处理发送的请求，而Hessian的这个远程过程调用，完全使用动态代理来实现的,，建议采用面向接口编程，Hessian服务通过接口暴露。

Hessian处理过程示意图：

客户端——>序列化写到输出流——>远程方法(服务器端)——>序列化写到输出流 ——>客户端读取输入流——>输出结果

下面详细介绍最常用的两种方式实现Hessian提供webservice：

纯Hessian实现

配合Spring框架实现

在开始之前当然需要到官网上下载相关的lib包，放入项目的/WEB-INF/lib/下

【一】、纯Hessian实现步骤：

1.基本代码

首先编写一个服务的接口类：HelloHessian.java

Java代码

package michael.hessian;
import java.util.List;
import java.util.Map;

/**
* @author michael
*
*/
public interface HelloHessian {

String sayHello();

MyCar getMyCar();

List myLoveFruit();

Map myBabays();

}

一个java bean文件MyCar.java:

Java代码

package michael.hessian;

import java.io.Serializable;

/**
* @author michael
*
*/
public class MyCar implements Serializable {

/**
*
*/
private static final long serialVersionUID = 4736905401908455439L;

private String carName;

private String carModel;

/**
* @return the carName
*/
public String getCarName() {
return carName;
}

/**
* @return the carModel
*/
public String getCarModel() {
return carModel;
}

/**
* @param pCarName the carName to set
*/
public void setCarName(String pCarName) {
carName = pCarName;
}

/**
* @param pCarModel the carModel to set
*/
public void setCarModel(String pCarModel) {
carModel = pCarModel;
}

/**
* @see java.lang.Object#toString()
* @return
*/
@Override
public String toString() {
return "my car name:[" + this.carName + "] model:[" + this.carModel
+ "].";
}

}

服务端接口的实现类：HelloHessianImpl.java

Java代码

package michael.hessian.impl;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import michael.hessian.HelloHessian;
import michael.hessian.MyCar;

/**
* @author michael
*
*/
public class HelloHessianImpl extends HessianServlet implements HelloHessian {

public MyCar getMyCar() {
MyCar car = new MyCar();
car.setCarName("阿斯顿·马丁");
car.setCarModel("One-77");
return car;
}

public Map myBabays() {
Map map = new HashMap();
map.put("son", "孙吴空");
map.put("daughter", "孙小美");
return map;
}

public List myLoveFruit() {
List list = new ArrayList();
list.add("apple");
list.add("kiwi");
list.add("orange");
return list;
}

public String sayHello() {
return "welcom to Hessian";
}

}

2.配置文件web.xml修改

在web.xml配置文件里增加如下信息：

Xml代码

<servlet>
<servlet-name>HelloHessianservlet-name>
<servlet-class>
com.caucho.hessian.server.HessianServlet
servlet-class>
<init-param>
<param-name>home-classparam-name>
<param-value>michael.hessian.impl.HelloHessianImplparam-value>
init-param>
<init-param>
<param-name>home-apiparam-name>
<param-value>michael.hessian.HelloHessianparam-value>
init-param>
<load-on-startup>1load-on-startup>
servlet>
<servlet-mapping>
<servlet-name>HelloHessianservlet-name>
<url-pattern>/HessianServiceurl-pattern>
servlet-mapping>
<servlet-mapping>

3.java客户端验证

Java代码

package michael.hessian.client;

import java.net.MalformedURLException;
import java.util.Map;

import michael.hessian.HelloHessian;
import michael.hessian.MyCar;

import com.caucho.hessian.client.HessianProxyFactory;

/**
* @author michael
*
*/
public class HessianClientTest {

/**
* @param args
*/
public static void main(String[] args) {
String url = "http://localhost:8082/J2EE_sjsky/HessianService";
HessianProxyFactory factory = new HessianProxyFactory();
try {
HelloHessian hello = (HelloHessian) factory.create(
HelloHessian.class, url);
System.out.println(hello.sayHello());

MyCar car = hello.getMyCar();
System.out.println(car.toString());

for (Map.Entry entry : hello.myBabays().entrySet()) {
System.out.println(entry.getKey() + "   " + entry.getValue());
}

for (String str : hello.myLoveFruit()) {
System.out.println(str);
}

} catch (MalformedURLException e) {
e.printStackTrace();
}

}

}

运行结果如下：

Java代码

welcom to Hessian
my car name:[阿斯顿·马丁] model:[One-77].
daughter   孙小美
son   孙吴空
apple
kiwi
orange

【二】、spring+hessian 实现服务端：

1.基本代码见上面的demo

2.修改配置文件

在web.xml，增加内容如下：

Xml代码

<servlet>
<servlet-name>springhessianservlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
servlet-class>

<bean name="/helloHessianService"
class="org.springframework.remoting.caucho.HessianServiceExporter">

<property name="service" ref="helloHessianImpl" />

<property name="serviceInterface"
value="michael.hessian.HelloHessian" />
bean>
beans>

3.java客户端验证

和上面的例子相似，只需要把访问的url替换成新的即可如下：

Java代码

String url=http://localhost:8082/J2EE_sjsky/springhessian/helloHessianService

运行结果和上面例子一样。

4.spring配置客户端

增加一个spring的bean配置文件hessian-client.xml

Xml代码

xml version="1.0" encoding="UTF-8"?>
>
<beans>
<bean id="helloHessianClient"
class="org.springframework.remoting.caucho.HessianProxyFactoryBean">
<property name="serviceUrl">
<value> http://localhost:8082/J2EE_sjsky/springhessian/helloHessianService value>
property>
<property name="serviceInterface"
value="michael.hessian.HelloHessian" />
bean>
beans>

测试代码HessianSpringClient.java：

Java代码

package michael.hessian.client;

import java.util.Map;

import michael.hessian.HelloHessian;
import michael.hessian.MyCar;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
* @author michael
*
*/
public class HessianSpringClient {

/**
* @param args
*/
public static void main(String[] args) {
try {
ApplicationContext context = new ClassPathXmlApplicationContext(
"hessian-client.xml");

HelloHessian hello = (HelloHessian) context
.getBean("helloHessianClient");

System.out.println(hello.sayHello());

MyCar car = hello.getMyCar();
System.out.println(car.toString());

for (Map.Entry entry : hello.myBabays().entrySet()) {
System.out.println(entry.getKey() + "   " + entry.getValue());
}

for (String str : hello.myLoveFruit()) {
System.out.println(str);
}
} catch (Exception e) {
e.printStackTrace();
}

}

}

运行结果和上面完全一致。

5.com.caucho.hessian.io.HessianProtocolException: expected string at 0x6d异常处理

我在spring+hessian整合测试过程中，客户端调用时，发生了异常，而服务端错误内容如下：

Java代码

2011-4-25 16:14:44 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet remoting threw exception
com.caucho.hessian.io.HessianProtocolException: expected string at 0x6d
at com.caucho.hessian.io.Hessian2Input.error(Hessian2Input.java:2882)
at com.caucho.hessian.io.Hessian2Input.expect(Hessian2Input.java:2830)
at com.caucho.hessian.io.Hessian2Input.readString(Hessian2Input.java:1362)
at com.caucho.hessian.io.Hessian2Input.readMethod(Hessian2Input.java:272)
at com.caucho.hessian.server.HessianSkeleton.invoke(HessianSkeleton.java:249)
at com.caucho.hessian.server.HessianSkeleton.invoke(HessianSkeleton.java:221)
at org.springframework.remoting.caucho.Hessian2SkeletonInvoker.invoke(Hessian2SkeletonInvoker.java:67)
at org.springframework.remoting.caucho.HessianServiceExporter.handleRequest(HessianServiceExporter.java:147)
at org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter.handle(HttpRequestHandlerAdapter.java:49)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:819)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:754)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:399)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:364)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)

经查资料发现原始是hessian和spring的版本不兼容引起的，重新下载hessian-3.1.6.jar导入项目，一起运行正常，测试完全通过。