[转]Hessian——轻量级远程调用方案

Hessian是caucho公司开发的一种基于二进制RPC协议(Remote Procedure Call protocol)的轻量级远程调用框架。具有多种语言的实现,但用的最多的当然是Java实现 :)

Creating a Hessian service using Java has four steps:

1、Create an Java interface as the public API
2、Create a client using HessianProxyFactory
3、Create the Service implementation class
4、Configure the service in your servlet engine.

下面,我们来实现1个例子:

首先下载hessian-4.0.37.jar,服务端和客户端都要用的。

然后编写程序。

server端:

package com.lin.hessian.service;
public interface Basic {
    public String sayHello();
}
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package com.lin.hessian.service;
public class BasicService implements Basic{
    private String message = "balalala!";
    @Override
    public String sayHello() {
        return message;
    }
}
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package com.lin.hessian.service;
import com.caucho.hessian.server.HessianServlet;
public class LinyService extends HessianServlet implements Basic{
    private String message = "wowwowowowowow";
    @Override
    public String sayHello() {
        return message;
    }
}
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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>HessianWeb</display-name>
  <servlet>     
        <servlet-name>hello</servlet-name>     
        <servlet-class>com.caucho.hessian.server.HessianServlet</servlet-class>     
        <init-param>     
            <param-name>home-class</param-name>     
            <param-value>com.lin.hessian.service.BasicService</param-value>     
        </init-param>     
        <init-param>     
            <param-name>home-api</param-name>
            <param-value>com.lin.hessian.service.Basic</param-value>     
        </init-param>     
    </servlet>
    
    <servlet-mapping>     
        <servlet-name>hello</servlet-name>     
        <url-pattern>/hello</url-pattern>     
    </servlet-mapping>

    <servlet>     
        <servlet-name>liny</servlet-name>     
        <servlet-class>com.lin.hessian.service.LinyService</servlet-class>         
    </servlet>
    
    <servlet-mapping>     
        <servlet-name>liny</servlet-name>
        <url-pattern>/liny</url-pattern>     
    </servlet-mapping>
</web-app>
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在服务端其实定义了两个service: BasicService和LinyService,不同之处在于是否继承HessianServlet,BasicService是一个pojo,而LinyService是一个servlet。

在web.xml里,BasicService是通过home-class和home-api两个参数传递给HessianServlet,然后将HessianServlet配置到web.xml的<servlet>里来实现服务配置到容器的。

而LinyService是直接将自己(它自己就是个Servlet)配置到web.xml的<servlet>来实现配置到容器。如果我们在一个应用中要实现多个hessian服务,应该采用这种方式。

下面来看看客户端:

package com.liny.hessian.service;
public interface Basic {
    public String sayHello();
}
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package com.lin.hessian.client;
import java.net.MalformedURLException;
import com.caucho.hessian.client.HessianProxyFactory;
import com.liny.hessian.service.Basic;
public class HessianClient {
    public static void main(String[] args) throws MalformedURLException{
     //String url = "http://localhost:8080/HessianWeb/hello"; String url = "http://localhost:8080/HessianWeb/liny"; HessianProxyFactory factory = new HessianProxyFactory(); Basic basic = (Basic)factory.create(Basic.class, url); System.out.println(basic.sayHello()); } }
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客户端要定义一个同服务端一模一样的接口Basic,然后通过HessianProxyFactory获得代理,并调用远程服务的方法。

注意:这里笔者故意将客户端与服务端的Basic接口的包路径定义成不一样(一个是com.liny.hessian.service,一个是com.lin.hessian.service),经过验证这样是可以的,但是推荐最好两者一模一样。

转载链接:http://www.cnblogs.com/lyhero11/p/5277583.html

原文地址:https://www.cnblogs.com/luohengstudy/p/7681393.html