一、什么是RPC
RPC全称Remote Procedure Call，中文名叫远程过程调用。RPC是一种远程调用技术，用于不同系统之间的远程相互调用。其在分布式系统中应用十分广泛。
二、什么是Hessian
Hessian是一个轻量级的RPC框架。 相比WebService，Hessian更简单、快捷。采用的是二进制RPC协议，因为采用的是二进制协议，所以它很适合于发送二进制数据。
三、Hessian的使用
1、引入jar包
<dependency>
<groupId>com.caucho</groupId>
<artifactId>hessian</artifactId>
<version>4.0.38</version>
</dependency>
2.编写业务代码（和普通的业务代码一样）
public interface UserService {
String getUserInfoById (Integer id);
}
@Component("uservice")
public class UserServiceImpl implements UserService {
@Autowired
private UserMapper userMapper;
public String getUserInfoById(Integer id) {
User user = userMapper.selectByPrimaryKey(id);
return user.toString();
}
}
3.创建并加载hessian-servlet.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
<!-- 使用Spring的HessianServie做代理 -->
<bean name="/userServiceImpl" class="org.springframework.remoting.caucho.HessianServiceExporter">
<!-- service引用具体的实现实体Bean-->
<property name="service" ref="uservice" />
<property name="serviceInterface" value="com.myproject.hessian.UserService" />
</bean> </beans>
public class HessianServiceProxyExporter extends HessianServiceExporter {
private static final Base64 base64 = new Base64();
@Override
public void handleRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String authorization = request.getHeader("Authorization");
if(authorization != null && authorization.length() > 0){
String userAndPwd = new String(base64.decode(authorization.split(" ")[1]));
String user = userAndPwd.split(":")[0];
String password = userAndPwd.split(":")[1];
if("user".equalsIgnoreCase(user) && "123456".equalsIgnoreCase(password)) {
super.handleRequest(request, response);
} else {
System.out.println("您无权调用");
}
}
}
}
<beans>
<!-- 自己定义代理类来继承org.springframework.remoting.caucho.HessianServiceExporter类，然后进行权限等一系列操作-->
<bean name="/userServiceImpl" class="com.myproject.hessian.exporter.HessianServiceProxyExporter">
<!-- service引用具体的实现实体Bean-->
<property name="service" ref="uservice" />
<property name="serviceInterface" value="com.myproject.hessian.UserService" />
</bean> </beans>
<!-- web.xml中进行拦截，并加载配置文件hessian -->
<servlet>
<servlet-name>hessian</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:hessian-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>hessian</servlet-name>
<url-pattern>/hessian/*</url-pattern>
</servlet-mapping>
5.客户端编写
①普通方式调用。同样需要引入hessian的jar包
//先将服务端的服务接口搬过来，包名和类名方法名最好是要一模一样
public interface UserService { String getUserInfoById (Integer id);
} public class Test { public static void main(String[] args) throws MalformedURLException {
String url = "http://localhost:8080/zmyproject/hessian/userServiceImpl";
HessianProxyFactory factory = new HessianProxyFactory();
factory.setUser("user");
factory.setPassword("123456")；
UserService userService = (UserService)factory.create(UserService.class, url);
System.out.println(userService.getUserInfoById(2));
}
}
②spring框架调用
Ⅰ、先引入jar包，注意jar包的版本我使用的hession-3.1.5.jar，启动会找不到一个factory类，所以用了4.0.38版本的。
Ⅱ、配置hession-client.xml，并加载该文件
<?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:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:task="http://www.springframework.org/schema/task"
xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
http://www.springframework.org/schema/task
http://www.springframework.org/schema/task/spring-task-3.1.xsd"> <!--客户端Hessian代理工厂Bean-->
<bean id="userService" class="org.springframework.remoting.caucho.HessianProxyFactoryBean">
<!--这是因为接口中出现方法重载，在调用时，服务器端会跑出异常 。在整合spring中，在客户端的配置里面加上如下代码可以解决：-->
<property name="overloadEnabled" value="true" />
<!--请求代理Servlet路径：-->
<property name="serviceUrl" value="http://localhost:8080/zmyproject/hessian/userServiceImpl" />
<!--接口定义：-->
<property name="serviceInterface" value="com.myproject.hessian.UserService" />
<property name="username" value="user" />
<property name="password" value="123456" />
</bean> </beans>
<!-- web.xml中配置 -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:hession-servlet.xml</param-value>
</context-param>
//和hessian服务端一样的接口
public interface UserService { String getUserInfoById (Integer id);
} @Controller//将该类标注为处理器，并且加入spring容器中
@RequestMapping("/hessian")
public class HessianController{ @Autowired
private UserService userService; @RequestMapping(value="/getInfo",method=RequestMethod.GET)
@ResponseBody
public String getInfo(HttpServletRequest request,HttpServletResponse response){
String userInfo = userService.getUserInfoById(1);
return userInfo;
} }