Question

它让我疯狂地试图解决这个问题。

我正在编写一个java服务器来处理android应用程序。它们传递文本字符串和xml。

目前简单的套接字通信看起来很好，但是当我尝试使用变压器而不是简单的println时，它会崩溃。

服务器代码如下

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.nio.charset.Charset;

import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;


public class javamultithreadedserver implements Runnable {
Socket csocket; 
static int listenport = 6021;
public static final String endOfCom = "endofcom";
String connectionname;

public javamultithreadedserver(Socket csocket, String connectionname) {
    this.csocket = csocket;
    this.connectionname = connectionname;
}

public static void main(String[] args) throws Exception {
    int listentoport = 0;
    //System.out.println(args.length);
    if (args.length == 1){
        listentoport = Integer.parseInt(args[0]);
    } else{
        listentoport = listenport;
    }
    ServerSocket ssock = new ServerSocket(listentoport);
    System.out.println("Listening at port " + listentoport);
    while (true) {
         Socket sock = ssock.accept();
         System.out.println("Connected. from: " + sock.getInetAddress().getHostAddress() + " " + sock.getInetAddress().getHostName() + " port: " + sock.getPort() + " " + sock.getInetAddress().getCanonicalHostName());
         new Thread(new javamultithreadedserver(sock, sock.getInetAddress().getHostAddress() + " " + sock.getInetAddress().getHostName() + " " + sock.getInetAddress().getCanonicalHostName())).start();
    }

}

@Override
public void run() {
      try {
          PrintWriter out = new PrintWriter(csocket.getOutputStream(), true);
          BufferedReader in = new BufferedReader(new InputStreamReader(csocket.getInputStream()));
          PrintStream pstream = new PrintStream (csocket.getOutputStream(), true);

          String inputLine, outputLine;

          System.out.println(connectionname + ": listening for query information.");
          while ((inputLine = in.readLine()) != null) {
              System.out.println(connectionname + ": " + inputLine);
              //out.write("received something");
              DBQuery q = new DBQuery(inputLine + DBQuery.regexsplit + "connectionname" + DBQuery.regexsplit + connectionname);
              DOMSource dmsource = q.returns();

              ***//StreamResult consoleResult = new StreamResult(System.out); //debug***
              StreamResult consoleResult = new StreamResult(pstream);
              TransformerFactory transformerFactory = TransformerFactory.newInstance();
              Transformer transformer = transformerFactory.newTransformer();
              Thread.sleep(100);
              ***transformer.transform(dmsource, consoleResult);***

              //out.println("println this is a testprogram"); // client receive ok

              pstream.flush();
              System.out.println(connectionname + ": reply sent.");

              if (inputLine == endOfCom){
                  System.out.println(connectionname + ": is satisfied and terminated communication.");
                  break;
              }
          }           
          pstream.close();
          csocket.close();
       }catch (IOException e) {
           System.out.println(e);
       }catch (Exception e) {
           System.out.println(e);
       }        
}
}

Android客户端代码如下：

public void run() {
if (barcode.length() > 0) {
    Socket socket = null;
    try {
        InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
        socket = new Socket(serverAddr, SERVERPORT);
        PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);

        socket.setSoTimeout(10000);
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

        out.write(barcode + ENDL);
        if(out.checkError()){
            showToUI("PrintWriter had error");
        } else {
            showToUI("Query sent");
        }
        int i = 0;
        while (true) {
            try{
                if (**(serverResponse = in.readLine()) != null**) {
                    if(serverResponse == endOfCom){
                        Log.i("communicated all data", "bye");
                        out.write(endOfCom + ENDL);
                        break;
                    } else{
                    }
                    Log.i("server says", serverResponse);
                }
                //Log.i("server says", (serverResponse == null? "null" :serverResponse ));
            }catch(SocketTimeoutException e){
                showToUI(barcode + ": Server did not respond in time");
                if (i++ > 2) {
                    break;
                }
            }
        }

    } catch (final UnknownHostException e1) {
        showToUI(e1.toString());
    } catch (final IOException e1) {
        showToUI(e1.toString());
    } finally{
        try {
            socket.close();
        } catch (IOException e) {
            showToUI(e.toString());
        }
    }
}else{
    runOnUiThread(new Runnable() {
        public void run() {
            Toast.makeText(getApplicationContext(), "Please enter something in barcode", Toast.LENGTH_SHORT).show();
        }
    });
}
}

我测试过返回的xml结果没问题，如果Stream Result设置为System.out而不是PrintStream pstream，那么一切都完美地打印到控制台。

无论是否有pstream.flush()，客户都未在(serverResponse = in.readLine()) != null收到回复。

同样，基于out socket的{{1}}套件的PrintWriter pstream成功地向客户提供了反馈。调用out.println("println this is a testprogram");后，客户端会在Log.i("server says", serverResponse);行接收日志确定。

有一点需要注意的是，回复通常很长，最多可达65536个字符甚至更多，我不知道是否有任何含义，我试图在android app上创建一个Buffered reader大于回复xml，它仍然无法正常工作。机器在本地网络上进行通信，java服务器程序在与Android模拟器不同的机器上运行。

感谢任何帮助，这已经持续了好几天。

Answer 1

在对等方关闭连接之前，

readLine()不会返回null。当它确实返回null时，你需要突破循环。并且不要将字符串s与==。

进行比较

变压器到插座不工作

1 个答案: