小试Hessian实现webservice

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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

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

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

    String sayHello();

    MyCar getMyCar();

    List<String> myLoveFruit();

    Map<String, String> myBabays();

}

一个java bean文件MyCar.java:

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

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

    public List<String> myLoveFruit() {
        List<String> list = new ArrayList<String>();
        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：

<servlet>
		<servlet-name>HelloHessian</servlet-name>
		<servlet-class>
			com.caucho.hessian.server.HessianServlet
		</servlet-class>
		<init-param>
			<param-name>home-class</param-name>
			<param-value>michael.hessian.impl.HelloHessianImpl</param-value>
		</init-param>
		<init-param>
			<param-name>home-api</param-name>
			<param-value>michael.hessian.HelloHessian</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>HelloHessian</servlet-name>
		<url-pattern>/HessianService</url-pattern>
	</servlet-mapping>
	<servlet-mapping>

3.java客户端验证

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<String, String> 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：

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：

<servlet>
		<servlet-name>springhessian</servlet-name>
		<servlet-class>
			org.springframework.web.servlet.DispatcherServlet
		</servlet-class>
		<!-- 
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>/WEB-INF/springhessian-servlet.xml</param-value>
		</init-param>
		 -->
		<load-on-startup>1</load-on-startup>
	</servlet>

	<servlet-mapping>
		<servlet-name>springhessian</servlet-name>
		<url-pattern>/springhessian/*</url-pattern>
	</servlet-mapping>

在/WEB-INF/增加一个叫servlet-name-servlet.xml配置文件。该文件的命名有一定的规则，红色servlet-name需要和web.xml中的<servlet-name>springhessian</servlet-name>定义的名称相匹配，比如本例子应叫springhessian-servlet.xml,这样简单也不容易出错。
当然该文件也可以自己任意命名。如果是自定义的文件名称不符合上述默认的规则，需要在<servlet>中增加<init-param>相关属性，人为指定加载配置文件，否则会报错。
范例：springhessian-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
	<bean id="helloHessianImpl"
		class="michael.hessian.impl.HelloHessianImpl" />
	<!-- 使用HessianServiceExporter 将bean生成Hessian服务-->
	<bean name="/helloHessianService"
		class="org.springframework.remoting.caucho.HessianServiceExporter">
		<!-- 定义需要生成服务的实现类-->
		<property name="service" ref="helloHessianImpl" />
		<!-- Hessian 提供服务的接口-->
		<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：

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 version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<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：

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<String, String> 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：

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)

经查资料发现原来是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，一切运行正常，测试完全通过。

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评论

2 楼 sjsky 2011-08-08  

ruijin5566 写道

very good

1 楼 ruijin5566 2011-08-08  

very good