Servlet传送对象给Applet使用

一起学习

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







 

        PostToApplet

        exapplet.MyServlet

    



 

        

            PostToApplet

        

        

            /exapplet/PostToApplet

        

    





第六步,编写html文件

呼叫更新的html













Hello This is a Test!















提取对象的html













Hello This is a Test!

中间有错误的地方请指教,[e-mail] 下载本文示例代码


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