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-namePostToApplet</servlet-name
<servlet-classexapplet.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
