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Servlet传送对象给Applet使用 |
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作者:未知 来源:月光软件站 加入时间:2005-2-28 月光软件站 |
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.
<pre> 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("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\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 <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN" "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd";> <web-app> <servlet> <servlet-name>PostToApplet</servlet-name> <servlet-class>exapplet.MyServlet</servlet-class> </servlet>
<servlet-mapping> <servlet-name> PostToApplet </servlet-name> <url-pattern> /exapplet/PostToApplet </url-pattern> </servlet-mapping> </web-app>
第六步,编写html文件 呼叫更新的html <HTML> <HEAD> <TITLE> New Document For Using Applet Call Servlet Update Java Object</TITLE> </HEAD>
<BODY> Hello This is a Test!<br> <APPLET id="obj_applet" align=center code="exapplet.MyApplet" codeBase="." width=400 height=300 name="obj_applet" archive="BV7RFD3P.ZIP"></APPLET> <Input type=button value="CallAppletMethod" onclick="callApplet()"> <Script language=javascript> function callApplet() { obj_applet.invoke(); } </Script> </BODY> </HTML>
提取对象的html <HTML> <HEAD> <TITLE> New Document For Using Applet </TITLE> </HEAD>
<BODY> Hello This is a Test!<br> <APPLET id="obj_applet" align=center code="exapplet.MyAppletB" codeBase="." width=400 height=300 name="obj_applet" archive="BV7RFD3P.ZIP"></APPLET> <Input type=button value="CallAppletMethod" onclick="callApplet()"> <Script language=javascript> function callApplet() { obj_applet.invoke(); } </Script> </BODY> </HTML> </pre>

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