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BufferedWriter 不刷新

[英]BufferedWriter does not flush

 原文  2012-08-05 15:25:40  2   4    java/ http/ sockets/ client-server/ printwriter

問題描述

我有以下問題....

            try 
            {
                clientInput = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                clientOutput = new BufferedWriter(new PrintWriter(clientSocket.getOutputStream()));

                while(true)
                { 
                    String clientRequest = "";
                    String tempStr = clientInput.readLine();

                    while(tempStr != null && !tempStr.equals("null"))
                    {
                        System.out.println(tempStr);
                        clientRequest += tempStr + " ";
                        tempStr = clientInput.readLine();
                    }

                    //Parse Request
                    ArrayList<String> tokenArray = parseRequest(clientRequest);

                    Calendar c = Calendar.getInstance();

                    switch(tokenArray.get(0))
                    {
                        case "GET": 
                        {
                            clientOutput.write("HTTP/1.1 200 OK\r\n");
                            clientOutput.write("Date: " + c.getDisplayName(0, Calendar.LONG, Locale.UK).toString() + "\r\n");
                            clientOutput.write("Server: Java HTTP Server v1.0\r\n");
                            clientOutput.flush();
                            break;
                            //Write File
                        }
                        default: 
                        {
                            clientOutput.write("500\r\n");
                            clientOutput.flush();
                        }
                    }
                } 
            }

每件事都完全正常，直到clientOutput.write("HTTP.......行，客戶端一直在等待......我試圖在每次連續寫入后刷新但什么也沒有。 ....但這是奇怪的部分 - 如果我在代碼進入 while 循環之前寫入並刷新，那么在case "GET":工作完美......即

代碼確實一直執行到

                            clientOutput.flush();
                            break;
                            //Write File

.

              try 
             {
                clientInput = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                clientOutput = new BufferedWriter(new PrintWriter(clientSocket.getOutputStream()));

                clientOutput.write("HTTP/1.1 200 OK\r\n");
                clientOutput.flush();

                while(true)
                { 
                    String clientRequest = "";
                    String tempStr = clientInput.readLine();

                    while(tempStr != null && !tempStr.equals("null"))
                    {
                        System.out.println(tempStr);
                        clientRequest += tempStr + " ";
                        tempStr = clientInput.readLine();
                    }

                    //Parse Request
                    ArrayList<String> tokenArray = parseRequest(clientRequest);

                    Calendar c = Calendar.getInstance();

                    switch(tokenArray.get(0))
                    {
                        case "GET": 
                        {
                            clientOutput.write("HTTP/1.1 200 OK\r\n");
                            clientOutput.write("Date: " + c.getDisplayName(0, Calendar.LONG, Locale.UK).toString() + "\r\n");
                            clientOutput.write("Server: Java HTTP Server v1.0\r\n");
                            clientOutput.flush();
                            break;
                            //Write File
                        }

這是客戶端的代碼

        Socket s = new Socket("localhost", 1337);

        BufferedReader fromServer = new BufferedReader(new InputStreamReader(s.getInputStream()));
        BufferedWriter toServer = new BufferedWriter(new PrintWriter(s.getOutputStream()));

        toServer.write("GET index.html HTTP/1.1\r\n");
        toServer.write("HOST: 127.0.0.1\r\n");
        toServer.write("Connection: close\r\n");
        toServer.write("\r\n");
        toServer.write("null\r\n");
        toServer.flush();   

        while(true)
        {
            String ss = fromServer.readLine();
            if(ss != null && !ss.equals("null"))
                System.out.println(ss);
        }

服務器等級：Strydom_A_201103578_P03

public class Strydom_A_201103578_P03
{
    Thread[] threadArray = new Thread[5];
    int ClientCount = 0;

    public Strydom_A_201103578_P03() throws ClientSizeExceededException 
    {
        ServerSocket httpServer = null;
    try 
    {
        httpServer = new ServerSocket(1337);
    } 
    catch (IOException ex) 
    {
        Logger.getLogger(Strydom_A_201103578_P03.class.getName()).log(Level.SEVERE, null, ex);
    }

    while(true)
    {
        try
        {
            //Wait for connection

            Socket clientSocket = httpServer.accept();

            if(ClientCount < 5)
            {
                threadArray[ClientCount] = new Thread(new clientHandler(clientSocket));
                threadArray[ClientCount].start();
                ClientCount++;
            }
            else
            {
                throw new ClientSizeExceededException();
            }

        }
        catch(IOException ex)
        {

        }
        finally
        {

        }
    }
}

class clientHandler implements Runnable
{
    Socket clientSocket;
    public clientHandler(Socket clientSocket) 
    {
        this.clientSocket = clientSocket;
    }

    @Override
    public void run() 
    {
        BufferedReader clientInput = null;
        BufferedWriter clientOutput = null;

            try 
            {
                clientInput = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                clientOutput = new BufferedWriter(new PrintWriter(clientSocket.getOutputStream()));

                clientOutput.write(" ");
                clientOutput.flush();

                while(true)
                { 
                    String clientRequest = "";
                    String tempStr = clientInput.readLine();

                    while(tempStr != null && !tempStr.equals("null"))
                    {
                        System.out.println(tempStr);
                        clientRequest += tempStr + " ";
                        tempStr = clientInput.readLine();
                    }

                    //Parse Request
                    ArrayList<String> tokenArray = parseRequest(clientRequest);

                    Calendar c = Calendar.getInstance();

                    switch(tokenArray.get(0))
                    {
                        case "GET": 
                        {
                            clientOutput.write("HTTP/1.1 200 OK\r\n");
                            clientOutput.write("Date: " + c.getDisplayName(0, Calendar.LONG, Locale.UK).toString() + "\r\n");
                            clientOutput.write("Server: Java HTTP Server v1.0\r\n");
                            clientOutput.flush();
                            break;
                            //Write File
                        }
                        default: 
                        {
                            clientOutput.write("500\r\n");
                            clientOutput.flush();
                        }
                    }
                } 
            }
            catch (IOException ex) 
            {
                Logger.getLogger(Strydom_A_201103578_P03.class.getName()).log(Level.SEVERE, null, ex);
            } 
            finally 
            {
                try 
                {
                    clientInput.close();
                    clientOutput.close();
                } 
                catch (IOException ex) 
                {
                    Logger.getLogger(Strydom_A_201103578_P03.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
    }

    private ArrayList<String> parseRequest(String tempStr) 
    {
        StringTokenizer httpTokens = new StringTokenizer(tempStr, " ");
        ArrayList<String> tokens = new ArrayList<>();

        while(httpTokens.hasMoreTokens())
            tokens.add(httpTokens.nextToken());

        return tokens;
    }
}


public static void main(String[] args) throws ClientSizeExceededException 
{
    new Strydom_A_201103578_P03();
}

}

public class TestClient 
{

public TestClient() 
{
    try 
    {
        Socket s = new Socket("localhost", 1337);

        BufferedReader fromServer = new BufferedReader(new InputStreamReader(s.getInputStream()));
        BufferedWriter toServer = new BufferedWriter(new PrintWriter(s.getOutputStream()));

        toServer.write("GET index.html HTTP/1.1\r\n");
        toServer.write("HOST: 127.0.0.1\r\n");
        toServer.write("Connection: close\r\n");
        toServer.write("\r\n");
        toServer.write("null\r\n");
        toServer.flush();   

        while(true)
        {
            String ss = fromServer.readLine();
            if(ss != null && !ss.equals("null"))
                System.out.println(ss);
        }

    } 
    catch (UnknownHostException ex) 
    {
        Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
    } 
    catch (IOException ex) 
    {
        Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
    }

}



public static void main(String[] args) 
{
    new TestClient();
}

}

客戶端類：TestClient

創建一個項目（或 2）並運行文件

4 個解決方案

解決方案1
 2 已采納  2012-08-05 22:50:15

這里的問題是PrintWriter 。 它吞下了異常。 將其更改為OutputStreamWriter 。 然后你會看到任何被吞噬的異常。 通常，您應該避免通過網絡使用PrintWriters和PrintOutputStreams 。 他們吞下了您需要了解的異常。

解決方案2
 0  2012-08-05 15:34:49

您需要更改內部 while 循環以查找客戶端請求的結尾：

while(tempStr != null && !tempStr.equals("null"))

到：

while(tempStr != null && !tempStr.equals("null") && !tempStr.equals(""))

客戶端在發送請求后不會斷開連接（導致空）。 它會給你一個空行來表示它的請求結束。

立即返回響應標頭的原因是有效的？ 也許客戶端只是讀取 200 並（最終）斷開連接？ 因此，當您閱讀客戶的請求時，它會結束並且您最終會得到一個空值。

編輯：

所以運行你的代碼，它對我來說很好用。 客戶端和服務器都在發送和接收請求和響應。 但是，服務器永遠不會斷開連接（客戶端包含一個Connection: close標頭）並且客戶端會繼續阻塞readLine() 。 毫不奇怪，當我在服務器端設置連接后立即包含write()和flush()時，除了在客戶端看到兩次HTTP/1.1 200 OK之外沒有任何變化。 也許您需要做的就是在try/catch{}結束時在finally{}塊中關閉clientSocket ？

解決方案3
 0  2012-08-05 18:12:26

所以為了讓我現在結束的痛苦變得更糟——這就是我最終所做的……

我將服務器和客戶端讀取器從BufferedReader/Writer更改為DataInputstream/OutputStream .... 現在它運行良好 - ！ 謝謝大家

艾登

解決方案4
 0  2016-02-09 16:57:25

我有以下問題......

            try 
            {
                clientInput = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                clientOutput = new BufferedWriter(new PrintWriter(clientSocket.getOutputStream()));

                while(true)
                { 
                    String clientRequest = "";
                    String tempStr = clientInput.readLine();

                    while(tempStr != null && !tempStr.equals("null"))
                    {
                        System.out.println(tempStr);
                        clientRequest += tempStr + " ";
                        tempStr = clientInput.readLine();
                    }

                    //Parse Request
                    ArrayList<String> tokenArray = parseRequest(clientRequest);

                    Calendar c = Calendar.getInstance();

                    switch(tokenArray.get(0))
                    {
                        case "GET": 
                        {
                            clientOutput.write("HTTP/1.1 200 OK\r\n");
                            clientOutput.write("Date: " + c.getDisplayName(0, Calendar.LONG, Locale.UK).toString() + "\r\n");
                            clientOutput.write("Server: Java HTTP Server v1.0\r\n");
                            clientOutput.flush();
                            break;
                            //Write File
                        }
                        default: 
                        {
                            clientOutput.write("500\r\n");
                            clientOutput.flush();
                        }
                    }
                } 
            }

一切正常，直到clientOutput.write("HTTP.......行，客戶端一直在等待和等待......我試圖在每次連續寫入后刷新，但沒有。 .... 但這是奇怪的部分 - 如果我在代碼進入 while 循環之前寫入並刷新，則case "GET":的寫入工作完美......即

代碼確實一直執行到

                            clientOutput.flush();
                            break;
                            //Write File

.

              try 
             {
                clientInput = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                clientOutput = new BufferedWriter(new PrintWriter(clientSocket.getOutputStream()));

                clientOutput.write("HTTP/1.1 200 OK\r\n");
                clientOutput.flush();

                while(true)
                { 
                    String clientRequest = "";
                    String tempStr = clientInput.readLine();

                    while(tempStr != null && !tempStr.equals("null"))
                    {
                        System.out.println(tempStr);
                        clientRequest += tempStr + " ";
                        tempStr = clientInput.readLine();
                    }

                    //Parse Request
                    ArrayList<String> tokenArray = parseRequest(clientRequest);

                    Calendar c = Calendar.getInstance();

                    switch(tokenArray.get(0))
                    {
                        case "GET": 
                        {
                            clientOutput.write("HTTP/1.1 200 OK\r\n");
                            clientOutput.write("Date: " + c.getDisplayName(0, Calendar.LONG, Locale.UK).toString() + "\r\n");
                            clientOutput.write("Server: Java HTTP Server v1.0\r\n");
                            clientOutput.flush();
                            break;
                            //Write File
                        }

這是客戶端的代碼

        Socket s = new Socket("localhost", 1337);

        BufferedReader fromServer = new BufferedReader(new InputStreamReader(s.getInputStream()));
        BufferedWriter toServer = new BufferedWriter(new PrintWriter(s.getOutputStream()));

        toServer.write("GET index.html HTTP/1.1\r\n");
        toServer.write("HOST: 127.0.0.1\r\n");
        toServer.write("Connection: close\r\n");
        toServer.write("\r\n");
        toServer.write("null\r\n");
        toServer.flush();   

        while(true)
        {
            String ss = fromServer.readLine();
            if(ss != null && !ss.equals("null"))
                System.out.println(ss);
        }

服務器類別：Strydom_A_201103578_P03

public class Strydom_A_201103578_P03
{
    Thread[] threadArray = new Thread[5];
    int ClientCount = 0;

    public Strydom_A_201103578_P03() throws ClientSizeExceededException 
    {
        ServerSocket httpServer = null;
    try 
    {
        httpServer = new ServerSocket(1337);
    } 
    catch (IOException ex) 
    {
        Logger.getLogger(Strydom_A_201103578_P03.class.getName()).log(Level.SEVERE, null, ex);
    }

    while(true)
    {
        try
        {
            //Wait for connection

            Socket clientSocket = httpServer.accept();

            if(ClientCount < 5)
            {
                threadArray[ClientCount] = new Thread(new clientHandler(clientSocket));
                threadArray[ClientCount].start();
                ClientCount++;
            }
            else
            {
                throw new ClientSizeExceededException();
            }

        }
        catch(IOException ex)
        {

        }
        finally
        {

        }
    }
}

class clientHandler implements Runnable
{
    Socket clientSocket;
    public clientHandler(Socket clientSocket) 
    {
        this.clientSocket = clientSocket;
    }

    @Override
    public void run() 
    {
        BufferedReader clientInput = null;
        BufferedWriter clientOutput = null;

            try 
            {
                clientInput = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                clientOutput = new BufferedWriter(new PrintWriter(clientSocket.getOutputStream()));

                clientOutput.write(" ");
                clientOutput.flush();

                while(true)
                { 
                    String clientRequest = "";
                    String tempStr = clientInput.readLine();

                    while(tempStr != null && !tempStr.equals("null"))
                    {
                        System.out.println(tempStr);
                        clientRequest += tempStr + " ";
                        tempStr = clientInput.readLine();
                    }

                    //Parse Request
                    ArrayList<String> tokenArray = parseRequest(clientRequest);

                    Calendar c = Calendar.getInstance();

                    switch(tokenArray.get(0))
                    {
                        case "GET": 
                        {
                            clientOutput.write("HTTP/1.1 200 OK\r\n");
                            clientOutput.write("Date: " + c.getDisplayName(0, Calendar.LONG, Locale.UK).toString() + "\r\n");
                            clientOutput.write("Server: Java HTTP Server v1.0\r\n");
                            clientOutput.flush();
                            break;
                            //Write File
                        }
                        default: 
                        {
                            clientOutput.write("500\r\n");
                            clientOutput.flush();
                        }
                    }
                } 
            }
            catch (IOException ex) 
            {
                Logger.getLogger(Strydom_A_201103578_P03.class.getName()).log(Level.SEVERE, null, ex);
            } 
            finally 
            {
                try 
                {
                    clientInput.close();
                    clientOutput.close();
                } 
                catch (IOException ex) 
                {
                    Logger.getLogger(Strydom_A_201103578_P03.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
    }

    private ArrayList<String> parseRequest(String tempStr) 
    {
        StringTokenizer httpTokens = new StringTokenizer(tempStr, " ");
        ArrayList<String> tokens = new ArrayList<>();

        while(httpTokens.hasMoreTokens())
            tokens.add(httpTokens.nextToken());

        return tokens;
    }
}


public static void main(String[] args) throws ClientSizeExceededException 
{
    new Strydom_A_201103578_P03();
}

}

public class TestClient 
{

public TestClient() 
{
    try 
    {
        Socket s = new Socket("localhost", 1337);

        BufferedReader fromServer = new BufferedReader(new InputStreamReader(s.getInputStream()));
        BufferedWriter toServer = new BufferedWriter(new PrintWriter(s.getOutputStream()));

        toServer.write("GET index.html HTTP/1.1\r\n");
        toServer.write("HOST: 127.0.0.1\r\n");
        toServer.write("Connection: close\r\n");
        toServer.write("\r\n");
        toServer.write("null\r\n");
        toServer.flush();   

        while(true)
        {
            String ss = fromServer.readLine();
            if(ss != null && !ss.equals("null"))
                System.out.println(ss);
        }

    } 
    catch (UnknownHostException ex) 
    {
        Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
    } 
    catch (IOException ex) 
    {
        Logger.getLogger(TestClient.class.getName()).log(Level.SEVERE, null, ex);
    }

}



public static void main(String[] args) 
{
    new TestClient();
}

}

客戶端類：TestClient

創建一個項目（或 2）並運行文件

解決方案5
 -1  2012-08-05 15:53:10

只要這樣做，它就會起作用…………

在PrintWriter中添加true作為第二個參數

clientOutput = new BufferedWriter(new PrintWriter(clientSocket.getOutputStream(), true));

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