这个违例是因何而产生?如何消除？

Question

你可以看看你的程序是不是在关闭了socket链接后，又进行了socket通讯。

Answer 1

注意：关闭Socket的位置是否恰当、是否flush?

Answer 2

我把Applet和Servlet的程序贴上来，两位请看看有什么不妥的地方

Answer 3

Applet的代码，文件名是：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();
      out.close();
      byteout.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());      
   }   
}

Answer 4

Servlet的代码，文件名是：PostServer.java
/**
 * version 1.00 1999-08-27
 * author Cay Horstmann
 */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
DataInputStream in=new DataInputStream(req.getInputStream());
strChoice=in.readUTF().trim();
System.out.println("strChoice="+strChoice);
in.close();

//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);
servletout.close();
byteout.close();
out.close();

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

}

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

Answer 5

flytsu(卡休) & Mailbomb(网络咖啡)　拜托，代码已经贴上来了，能否看一下？谢谢

Answer 6

byteout.close();
out.close();变一下顺序，out.close()应该在前面

Answer 7

to xiangqian(天阁流云):
照作了但还是有相同违例被掷出

Answer 8

try to close "in" after you call servletout.write(buf). 

Answer 9

servlet有一个public void destroy(){}，在这里面关闭socket

Answer 10

to wwangl(???)能够在详细点吗？谢谢

Answer 11

试一下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
DataInputStream in=new DataInputStream(req.getInputStream());
strChoice=in.readUTF().trim();
System.out.println("strChoice="+strChoice);
in.close();//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{
    servletout.close();
    byteout.close();
    out.close();
  }catch(Exception e){System.out.println(e);}private String strChoice;
private byte[] buf;
private ServletOutputStream servletout;
private ByteArrayOutputStream byteout;
private DataOutputStream out;}

Answer 12

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

Answer 13

to wwangl(???)
谢谢用你的方法问题解决了，给分