所属类别：JSP

文章作者：未知

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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Servletpackage 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Appletpackage 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Appletpackage 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\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htmlHello This is a Test!function callApplet(){ obj_applet.invoke();}提取对象的htmlHello This is a Test!function callApplet(){ obj_applet.invoke();}中间有错误的地方请指教,zlyperson@163.net关闭本页 首页 投资与合作 服务条款 隐私政策 收藏本站 设为首页 新用户注册 免责声明 使用帮助Copyright ©2005-2008 chinaitpower.com All rights reserved. www.chinaitpower.com 版权所有

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