因为公司的项目远程调用采用的是hessian，故抽时间了解了下hessian，自己也写了一个应用实例，以便加深对hessian的理解。
Hessian是一个轻量级的remoting onhttp工具，使用简单的方法提供了RMI的功能。 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。
在进行基于Hessian的项目开发时，应当注意以下几点：
JAVA服务器端必须具备以下几点：
·包含Hessian的jar包
·设计一个接口，用来给客户端调用
·实现该接口的功能
·配置web.xml，配好相应的servlet
·对象必须实现Serializable 接口
·对于复杂对象可以使用Map的方法传递
客户端必须具备以下几点：
·java客户端包含Hessian.jar的包。
·具有和服务器端结构一样的接口。包括命名空间都最好一样
·利用HessianProxyFactory调用远程接口。
以下是一个关于hessian应用的示例程序。
示例背景：
由于本人所在公司正在编码直播室方面的项目，故以下源码中用LiveRoom.java类为直播室的类。User.java类为用户类。直播室和用户之间为一对多的关系。即一个直播室里面有多个用户。本示例将实现对直播室的增删改查功能
我们先写服务端
服务端，即提供服务的一端（废话，呵呵），需要定义接口，并提供接口实现。
首先，定义两个类LiveRoom和User,并且两个类都要实现Serializable 接口
package org.study.hessian.domain;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
public class LiveRoom implements Serializable,Comparable<LiveRoom>{
private static final long serialVersionUID = -3219121209937741843L;
private int roomId;
private String roomName;
public List<User> users = new ArrayList<User>();
public LiveRoom(int roomId, String roomName) {
super();
this.roomId = roomId;
this.roomName = roomName;
}
public LiveRoom() {
super();
}
public int getRoomId() {
return roomId;
}
public void setRoomId(int roomId) {
this.roomId = roomId;
}
public String getRoomName() {
return roomName;
}
public void setRoomName(String roomName) {
this.roomName = roomName;
}
public int compareTo(LiveRoom o) {
if(this.getRoomId() > o.getRoomId()){
return 1;
}
else if(this.getRoomId() < o.getRoomId()){
return -1;
}
else
{
return 0;
}
}
}
package org.study.hessian.domain;
import java.io.Serializable;
import java.util.Date;
public class User implements Serializable{
private int userId;
private String userName;
private Date birth;
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public Date getBirth() {
return birth;
}
public void setBirth(Date birth) {
this.birth = birth;
}
}
然后定义接口
package org.study.hessian.service;
import java.util.List;
import org.study.hessian.domain.LiveRoom;
public interface LiveRoomService {
public abstract void addRoom(LiveRoom room);
public abstract void delRoom(int roomId);
public abstract void updateRoom(LiveRoom room);
public abstract LiveRoom getRoomById(int roomId);
public abstract List<LiveRoom> getAllRoom();
}
接口的实现
package org.study.hessian.service.impl;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.study.hessian.domain.LiveRoom;
import org.study.hessian.service.LiveRoomService;
public class LiveRoomServiceImpl implements LiveRoomService {
public Map<Integer, LiveRoom> roomMap = new HashMap<Integer, LiveRoom>();
public void addRoom(LiveRoom room) {
roomMap.put(room.getRoomId(), room);
}
public void delRoom(int roomId) {
roomMap.remove(roomId);
}
public List<LiveRoom> getAllRoom() {
List<LiveRoom> list = new ArrayList<LiveRoom>();
Collection<LiveRoom> coll = roomMap.values();
Iterator<LiveRoom> it = coll.iterator();
while(it.hasNext()){
LiveRoom room = it.next();
list.add(room);
}
Collections.sort(list);
return list;
}
public LiveRoom getRoomById(int roomId) {
return roomMap.get(roomId);
}
public void updateRoom(LiveRoom room) {
roomMap.remove(room.getRoomId());
roomMap.put(room.getRoomId(), room);
}
}
配置web.xml，配好相应的servlet
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>liveRoom</servlet-name>
<servlet-class>
com.caucho.hessian.server.HessianServlet
</servlet-class>
<init-param>
<!-- home-class也可以写为service-class -->
<param-name>home-class</param-name>
<!-- 服务器对接口的现实，供客户端调用 -->
<param-value>
org.study.hessian.service.impl.LiveRoomServiceImpl
</param-value>
</init-param>
<init-param>
<!--home-api也可以写为api-class -->
<param-name>home-api</param-name>
<!-- 客户端接口 -->
<param-value>org.study.hessian.service.LiveRoomService</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>liveRoom</servlet-name>
<url-pattern>/liveRoom</url-pattern>
</servlet-mapping>
</web-app>
至此，服务端的代码就写完了。
接着，我们写客户端
注：客户端需要服务端定义的两个类和定义的接口（不需要接口的实现）
客户端的调用代码如下：
package org.study.hessian;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import org.study.hessian.api.LiveRoomService;
import org.study.hessian.domain.LiveRoom;
import org.study.hessian.domain.User;
import org.study.hessian.utils.PropertyFileUtil;
import com.caucho.hessian.client.HessianProxyFactory;
public class Test {
public static void main(String[] args) throws MalformedURLException,
ClassNotFoundException {
// 远程调用地址
String url="http://localhost:8080/HessianServer/liveRoom";
System.out.println(url);
HessianProxyFactory factory = new HessianProxyFactory();
LiveRoomService liveRoomService = (LiveRoomService) factory.create(
LiveRoomService.class, url);
for (int i = 1; i < 10; i++) {
LiveRoom room = new LiveRoom();
room.setRoomId(i);
room.setRoomName("liveRoom" + i);
List<User> list = new ArrayList<User>();
for (int j = 1; j < 5; j++) {
User user = new User();
user.setUserId(j);
user.setUserName("xiongyuewen" + j);
user.setBirth(new Date());
list.add(user);
}
room.users = list;
liveRoomService.addRoom(room);
}
liveRoomService.delRoom(3);
LiveRoom room = new LiveRoom();
room.setRoomId(4);
room.setRoomName("wanglili");
room.users = null;
liveRoomService.updateRoom(room);
List<LiveRoom> listRooms = liveRoomService.getAllRoom();
if (listRooms == null) {
throw new RuntimeException("listRooms is null");
}
for (LiveRoom lr : listRooms) {
System.out.println(lr.getRoomName());
List<User> users = lr.users;
if (users == null) {
continue;
}
for (User user : users) {
System.out.println(user.getUserName() + " " + user.getBirth());
}
}
}
}