Servlet传送对象给Applet使用 (转)[@more@]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:XSchoolWorkingRoomexappletsrcjava.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("http://rookie:8080/workingroom/exapplet/PostToApplet?Action=UpdateObject";); 
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("http://rookie:8080/workingroom/exapplet/PostToApplet?Action=GetObject";); 
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

-Name: "+p.getName()+"
-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 
 



ping> 
 
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!