applet和servlet通信的菜鸟问题（一定给分！）

fallingkent 2002-03-15 10:39:38

在一个project里编了一个applet和一个servlet，把他们放到服务器端了。在applet中应该怎样调用那个servlet呢？看一个例子说这样：

URL theURL = new URL("http://servername/myservlet");
theURL.openStream();

可是不成啊，那个myservlet的名字用.class或者不用都不行。
应该如何通信？

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fallingkent 2002-03-16

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服务器不是我配置的，我也不知道。

看来这是一个错误的选择，不如在服务器上直接放一个application算了

magus_yang 2002-03-16

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你用jswdk还是tomcat?

fallingkent 2002-03-15

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你这里也是通过
url=new URL("http://localhost/PostServer");
con=url.openConnection();
来操作的，可是我把它放在服务器上就
Exception : java.io.FileNotFoundException: File not found
要怎么设置它的名字吗？

peacock_king 2002-03-15

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去www.cn-java.com看看，讲得很清楚。

magus_yang 2002-03-15

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rmi看了，不过一直没时间实践一下

socket用vc和vb写多了，java应该不会有很大差别。这就是没有实践的理由，呵呵

corba没看过，你要另请高明了，呵呵

magus_yang 2002-03-15

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下面是我写的post的例子，三部分applet,servlet和嵌有applet的网页
//PostClient.java
import java.net.*;
import java.io.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;

class PostClientPanel extends JPanel implements ActionListener
{
public PostClientPanel()
{
strOutput=new String("输出初始化!");
vctFromServ.clear();
vctFromServ.add("输入初始化!");

cmdStep1=new JButton("第一步");
cmdStep2=new JButton("第二步");

add(cmdStep1);
add(cmdStep2);

cmdStep1.addActionListener(this);
cmdStep2.addActionListener(this);

}

public void actionPerformed(ActionEvent evt)
{
Object source=evt.getSource();
if(source==cmdStep1)
{
strOutput="第一步";
try
{
//向server发送消息
System.out.println("Before Step1 connection!");
url=new URL("http://localhost/PostServer");
con=url.openConnection();
con.setUseCaches(false);
con.setDoOutput(true);
con.setDoInput(true);
ByteArrayOutputStream byteout=new ByteArrayOutputStream();
DataOutputStream out=new DataOutputStream(byteout);
out.writeUTF("第一步");
out.flush();
byte buf[]=byteout.toByteArray();
con.setRequestProperty("Content-type","application/octet-stream");
con.setRequestProperty("Content-length",""+buf.length);
DataOutputStream dataout=new DataOutputStream(con.getOutputStream());
dataout.write(buf);
dataout.flush();
dataout.close();
byteout.close();
out.close();

}
catch(IOException e)
{
System.out.println("OUTPUT ERROR:"+e);
}
try
{
//从server接收消息
DataInputStream in=new DataInputStream(con.getInputStream());
vctFromServ.clear();
String strInput;
while((strInput=in.readUTF())!=null)
{
vctFromServ.add(strInput);
}
in.close();
}
catch(IOException e)
{
System.out.println("INPUT Error " + e);
}
}
else
{
strOutput="第二步";
try
{

System.out.println("Before Step2 connection!");
url=new URL("http://localhost/PostServer");
con=url.openConnection();
con.setUseCaches(false);
con.setDoOutput(true);
con.setDoInput(true);
ByteArrayOutputStream byteout=new ByteArrayOutputStream();
DataOutputStream out=new DataOutputStream(byteout);
out.writeUTF("第二步");
out.flush();
byte buf[]=byteout.toByteArray();
con.setRequestProperty("Content-type","application/octet-stream");
con.setRequestProperty("Content-length",""+buf.length);
DataOutputStream dataout=new DataOutputStream(con.getOutputStream());
dataout.write(buf);
dataout.flush();
dataout.close();

DataInputStream in=new DataInputStream(con.getInputStream());
vctFromServ.clear();
String strInput;
while((strInput=in.readUTF())!=null)
{
vctFromServ.add(strInput);
}
}
catch(IOException e)
{
System.out.println("Error " + e);
}
}
repaint();
}

public void paintComponent(Graphics g)
{
super.paintComponent(g);
g.drawString(strOutput,200,200);
int tmpX=200;
int tmpY=250;
for(int i=0;i<vctFromServ.size();i++)
{
g.drawString((String)vctFromServ.elementAt(i),tmpX,tmpY);
tmpY+=50;
}
}

private String strOutput;
private Vector vctFromServ=new Vector();
private JButton cmdStep1;
private JButton cmdStep2;
private URL url;
private URLConnection con;
}

public class PostClient extends JApplet

{ public void init()
{ Container contentPane = getContentPane();
contentPane.add(new PostClientPanel());

}

}

//PostServer.java
import java.io.*;
import java.net.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class PostServer extends HttpServlet
{
public void service(HttpServletRequest req,HttpServletResponse resp)
{
try
{
//接收从客户端发来的数据
in=new DataInputStream(req.getInputStream());
strChoice=in.readUTF().trim();
System.out.println("strChoice="+strChoice);

//向客户端发送数据
resp.setContentType("application/octet-stream");
byteout=new ByteArrayOutputStream();
out=new DataOutputStream(byteout);
if(strChoice.equals("第一步"))
{
out.writeUTF("第一步回复1!");
out.writeUTF("第一步回复2!");
}
else if(strChoice.equals("第二步"))
{
out.writeUTF("第二步回复1!");
out.writeUTF("第二步回复2!");
out.writeUTF("第二步回复3!");
out.writeUTF("第二步回复4!");
}
out.flush();

buf=byteout.toByteArray();
resp.setContentLength(buf.length);
servletout=resp.getOutputStream();
servletout.write(buf);

}
catch(IOException ex)
{
System.out.println("out3 ERROR:"+ex);
}

}

public void destroy()
{
try
{
in.close();
servletout.close();
byteout.close();
out.close();
}
catch(Exception e)
{
System.out.println(e);
}
}

private DataInputStream in;
private String strChoice;
private byte[] buf;
private ServletOutputStream servletout;
private ByteArrayOutputStream byteout;
private DataOutputStream out;

}

//PostClient.html
<html>
<title>xyAxisApplet</title>
<body>



<p>Applet和Servlet通讯测试:Post方法</p>
<OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93"
WIDTH = 400 HEIGHT = 400 codebase="http://java.sun.com/products/plugin/1.3/jinstall-13-win32.cab#Version=1,3,0,0">
<PARAM NAME = CODE VALUE = "PostClient" >

<PARAM NAME="type" VALUE="application/x-java-applet;version=1.3">
<PARAM NAME="scriptable" VALUE="false">

<COMMENT>
<EMBED type="application/x-java-applet;version=1.3" CODE = "PostClient" WIDTH = 400 HEIGHT = 400 scriptable=false pluginspage="http://java.sun.com/products/plugin/1.3/plugin-install.html"><NOEMBED></COMMENT>

</NOEMBED></EMBED>
</OBJECT>



</body>
</html>

magus_yang 2002-03-15