Servlet传送对象给Applet使用

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前日,一位朋友与我谈论Servlet与Applet共享Java对象的问题,现发表出来与大家分享,文中瑕癖
之处甚多,望各位指教.
朋友谈论的需求是这样的:他想通过页面上一个Applet呼叫一个服务器Servlet,而从Servlet产生
一个Java对象再传给另外一个Applet,怎么样让Servlet实时地把对象传给Applet这是一个问题,有一个方
案是采用JMS(JavaMessageService),在我以后的文章中会有叙述的.这里我给大家展示一个简单的实现,那
就是让Applet主动访问Servlet,让Servlet返回Java对象.下面给出全部代码和配置,其中Applet部分涵盖
了Javascript与Applet的互相调用,对于该部分不感兴趣的朋友可以复略.

第一步,编写需要传递的对象类
/**
* Class Person just a demo for translate this class to client
* @author:  rookie
* @datetime: 2002-7-26
*/
package exapplet;
import java.io.*;

public class Person implements Serializable {//必须实现Serializable接口才能序列化
private String m_Name;
private int  m_Age;

public Person() {
this("",0);
}
public Person(String name,int age) {
this.m_Name = name;
this.m_Age = age;
}
public String getName() {
return m_Name;
}
public int getAge() {
return m_Age;
}

//Serializable接口中声明的方法
private void writeObject(java.io.ObjectOutputStream out)
throws IOException {
out.defaultWriteObject();
}

//Serializable接口中声明的方法
private void readObject(java.io.ObjectInputStream in)
throws IOException, ClassNotFoundException {
in.defaultReadObject();
}

public static void main(String[] args) {
try {
Person p = new Person("Liaoyuan",25);
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File("test.obj")));
oos.writeObject(p);
oos.close();
ObjectInputStream ois = new ObjectInputStream (new FileInputStream(new File("test.obj")));
Person q = (Person)ois.readObject();
ois.close();
System.out.println(q.getName());
System.out.println(q.getAge());
} catch(Exception exp) {
exp.printStackTrace();
}
}
}

第二步,实现Servlet
package exapplet;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class MyServlet extends HttpServlet
{
public void doGet(HttpServletRequest req,HttpServletResponse res)
throws ServletException,IOException
{
String fPath = "H://XSchool//WorkingRoom//exapplet//src//java.obj";

String act = req.getParameter("Action");
if ( act.equals("UpdateObject") ) {
//创建更新JavaObject
Person p = new Person("Liaoyuan",26);
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(new File(fPath)));
oos.writeObject(p);
oos.close();
DataOutputStream dos = new DataOutputStream(res.getOutputStream());
dos.writeBytes("Server Java Object Updated OK!");
dos.close();
} else if ( act.equals("GetObject") ) {
//传回对象给Applet
res.setContentType("application/octet-stream");
Person p;
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File(fPath)));
try {
p    = (Person)ois.readObject();
} catch (ClassNotFoundException e) {
p = new Person();
}
ois.close();

ObjectOutputStream oos = new ObjectOutputStream(res.getOutputStream());
oos.writeObject(p);
oos.close();
}
}
public String getServletInfo()
{
return "A simple Servlet!";
}
}

第三步,实现呼叫Servlet更新对象的Applet
package exapplet;
import java.awt.*;
import java.applet.*;
import java.io.*;
import java.net.*;
import netscape.javascript.*;

public class MyApplet extends java.applet.Applet
{
public void init()
{
}
public void paint(Graphics g)
{}

//This method will be call in html
public void invoke() {
try {
URL url = new URL("");
URLConnection urlcon = url.openConnection();
urlcon.connect();

DataInputStream dis=new DataInputStream(urlcon.getInputStream());
String txt = dis.readLine();
dis.close();

String[] info = new String[]{txt};
JSObject.getWindow(this).call("alert",info);
} catch (Exception e) {
}
}
}

第四步,实现提取对象的Applet
package exapplet;
import java.awt.*;
import java.applet.*;
import java.io.*;
import java.net.*;
import netscape.javascript.*;

public class MyAppletB extends java.applet.Applet
{
public void init()
{
}
public void paint(Graphics g)
{}

//This method will be call in html
public void invoke() {
try {
URL url = new URL("");
URLConnection urlcon = url.openConnection();
urlcon.connect();
ObjectInputStream ois=new ObjectInputStream(urlcon.getInputStream());
Person p = (Person)ois.readObject();
ois.close();
String[] info = new String[]{"Person Info/n/n-Name: " p.getName() "/n-Age : " p.getAge()};
JSObject.getWindow(this).call("alert",info);
} catch (Exception e) {
}
}
}

第五步,配制WebServer(我用的是Tomcat4.0)
拷贝编译后的MyServlet.class到相应目录下,
编辑对应的web.xml文件,确保下面的内容正确

http://java.sun.com/j2ee/dtds/web-app_2_2.dtd">

PostToApplet
exapplet.MyServlet

PostToApplet

/exapplet/PostToApplet

第六步,编写html文件
呼叫更新的html

New Document For Using Applet Call Servlet Update Java Object

Hello This is a Test!

function callApplet()
{
obj_applet.invoke();
}

提取对象的html

New Document For Using Applet

Hello This is a Test!

function callApplet()
{
obj_applet.invoke();
}

中间有错误的地方请指教,zlyperson@163.net