Servlet传送对象给Applet使用

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 os = new ObjectOutputStream(new FileOutputStream(new File("test.obj")));oos.writeObject(p);oos.close();ObjectInputStream is = 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JavaObjectPerson p = new Person("Liaoyuan",26);ObjectOutputStream os = 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Appletres.setContentType("application/octet-stream");Person p;ObjectInputStream is = new ObjectInputStream(new FileInputStream(new File(fPath)));try {p　　= (Person)ois.readObject();} catch (ClassNotFoundException e) {p = new Person();}ois.close();ObjectOutputStream os = 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 htmlpublic 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 htmlpublic void invoke() {try {URL url = new URL("http://rookie:8080/workingroom/exapplet/PostToApplet?Action=GetObject");URLConnection urlcon = url.openConnection();urlcon.connect();ObjectInputStream is=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

PostToAppletexapplet.MyServletPostToApplet/exapplet/PostToApplet

第六步,编写html文件

呼叫更新的html

Hello This is a Test!function callApplet(){obj_applet.invoke();}

提取对象的html

Hello This is a Test!function callApplet(){obj_applet.invoke();}

我们可以沿途用镜头记录彼此的笑脸，和属于我们的风景。