我怎麼能讀Java控制檯輸出到字符串緩衝區

17

好吧，這是一個有趣的問題。 Dosen似乎是一次解決所有PrintStream方法的優雅方式。（不幸的是沒有FilterPrintStream）

我雖然寫了一個醜陋的基於反射的解決方法（而不是在生產代碼中使用我想:)

class LoggedPrintStream extends PrintStream { 

    final StringBuilder buf; 
    final PrintStream underlying; 

    LoggedPrintStream(StringBuilder sb, OutputStream os, PrintStream ul) { 
     super(os); 
     this.buf = sb; 
     this.underlying = ul; 
    } 

    public static LoggedPrintStream create(PrintStream toLog) { 
     try { 
      final StringBuilder sb = new StringBuilder(); 
      Field f = FilterOutputStream.class.getDeclaredField("out"); 
      f.setAccessible(true); 
      OutputStream psout = (OutputStream) f.get(toLog); 
      return new LoggedPrintStream(sb, new FilterOutputStream(psout) { 
       public void write(int b) throws IOException { 
        super.write(b); 
        sb.append((char) b); 
       } 
      }, toLog); 
     } catch (NoSuchFieldException shouldNotHappen) { 
     } catch (IllegalArgumentException shouldNotHappen) { 
     } catch (IllegalAccessException shouldNotHappen) { 
     } 
     return null; 
    } 
}

...可以像使用這樣的：

public class Test { 
    public static void main(String[] args) { 

     // Create logged PrintStreams 
     LoggedPrintStream lpsOut = LoggedPrintStream.create(System.out); 
     LoggedPrintStream lpsErr = LoggedPrintStream.create(System.err); 

     // Set them to stdout/stderr 
     System.setOut(lpsOut); 
     System.setErr(lpsErr); 

     // Print some stuff 
     System.out.print("hello "); 
     System.out.println(5); 
     System.out.flush(); 

     System.err.println("Some error"); 
     System.err.flush(); 

     // Restore System.out/System.err 
     System.setOut(lpsOut.underlying); 
     System.setErr(lpsErr.underlying); 

     // Print the logged output 
     System.out.println("----- Log for System.out: -----\n" + lpsOut.buf); 
     System.out.println("----- Log for System.err: -----\n" + lpsErr.buf); 
    } 
}

結果輸出：

hello 5 
Some error 
----- Log for System.out: ----- 
hello 5 

----- Log for System.err: ----- 
Some error

（注壽呃，FilterOutputStream中的out字段是受保護和記錄的，因此它是API的一部分:-)

來源

2010-12-02 13:28:25 aioobe

+1

哇！非常感謝。這個對我有用。 – Jacob 2010-12-03 05:49:28

5

一旦程序運行完畢，您就無法做到這一點。您需要在程序開始寫入輸出之前執行此操作。有關如何替換stdout和stderr的詳細信息，請參閱this article。核心電話是System.setOut()和System.setErr()。

來源

2010-12-02 12:12:10 unwind

0

不要做之後，在第一個System.out.print()被調用之前創建兩個StringBuilder對象，並將您想要保存的每個字符串追加到相應的StringBuilder。

來源

2010-12-02 12:12:41

1

您可以使用PipedInputStream和PipedOutputStream。

//create pairs of Piped input and output streasm for std out and std err 
final PipedInputStream outPipedInputStream = new PipedInputStream(); 
final PrintStream outPrintStream = new PrintStream(new PipedOutputStream(
    outPipedInputStream)); 
final BufferedReader outReader = new BufferedReader(
    new InputStreamReader(outPipedInputStream)); 
final PipedInputStream errPipedInputStream = new PipedInputStream(); 
final PrintStream errPrintStream = new PrintStream(new PipedOutputStream(
    errPipedInputStream)); 
final BufferedReader errReader = new BufferedReader(
    new InputStreamReader(errPipedInputStream)); 
final PrintStream originalOutStream = System.out; 
final PrintStream originalErrStream = System.err; 
final Thread writingThread = new Thread(new Runnable() { 
    @Override 
    public void run() { 
     try { 
      System.setOut(outPrintStream); 
      System.setErr(errPrintStream); 
      // You could also set the System.in here using a 
      // PipedInputStream 
      DoSomething(); 
      // Even better would be to refactor DoSomething to accept 
      // PrintStream objects as parameters to replace all uses of 
      // System.out and System.err. DoSomething could also have 
      // an overload with DoSomething() calling: 
      DoSomething(outPrintStream, errPrintStream); 
     } finally { 
      // may also want to add a catch for exceptions but it is 
      // essential to restore the original System output and error 
      // streams since it can be very confusing to not be able to 
      // find System.out output on your console 
      System.setOut(originalOutStream); 
      System.setErr(originalErrStream); 
      //You must close the streams which will auto flush them 
      outPrintStream.close(); 
      errPrintStream.close(); 
     } 
    } // end run() 
}); // end writing thread 
//Start the code that will write into streams 
writingThread.start(); 
String line; 
final List<String> completeOutputStreamContent = new ArrayList<String>(); 
while ((line = outReader.readLine()) != null) { 
    completeOutputStreamContent.add(line); 
} // end reading output stream 
final List<String> completeErrorStreamContent = new ArrayList<String>(); 
while ((line = errReader.readLine()) != null) { 
    completeErrorStreamContent.add(line); 
} // end reading output stream

來源

2012-07-06 14:50:21 PeterVermont

0

這兩行代碼會將您的輸出置於文本文件中，或者您可以根據需要更改目的地。

//創建一個文件： System.setOut（新的PrintStream（新FileOutputStream中（「d：/MyOutputFile.txt」）））; //將輸出重定向到文件： System.out.println（「Hello to custom output stream！」）;

希望其幫助你.. :)

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2013-03-17 08:17:11

0

這是一個實用工具類名爲ConsoleOutputCapturer。它允許輸出到現有控制檯，但在場景後面繼續捕獲輸出文本。您可以控制使用啓動/停止方法捕獲的內容。換句話說，調用start開始捕獲控制檯輸出，一旦完成捕獲，您可以調用stop方法，該方法返回一個String值，該值持有控制檯輸出，用於啓動和停止調用之間的時間窗口。這個類雖然不是線程安全的。

 

import java.io.ByteArrayOutputStream; 
import java.io.IOException; 
import java.io.OutputStream; 
import java.io.PrintStream; 
import java.util.Arrays; 
import java.util.List; 

public class ConsoleOutputCapturer { 
    private ByteArrayOutputStream baos; 
    private PrintStream previous; 
    private boolean capturing; 

    public void start() { 
     if (capturing) { 
      return; 
     } 

     capturing = true; 
     previous = System.out;  
     baos = new ByteArrayOutputStream(); 

     OutputStream outputStreamCombiner = 
       new OutputStreamCombiner(Arrays.asList(previous, baos)); 
     PrintStream custom = new PrintStream(outputStreamCombiner); 

     System.setOut(custom); 
    } 

    public String stop() { 
     if (!capturing) { 
      return ""; 
     } 

     System.setOut(previous); 

     String capturedValue = baos.toString();    

     baos = null; 
     previous = null; 
     capturing = false; 

     return capturedValue; 
    } 

    private static class OutputStreamCombiner extends OutputStream { 
     private List<OutputStream> outputStreams; 

     public OutputStreamCombiner(List<OutputStream> outputStreams) { 
      this.outputStreams = outputStreams; 
     } 

     public void write(int b) throws IOException { 
      for (OutputStream os : outputStreams) { 
       os.write(b); 
      } 
     } 

     public void flush() throws IOException { 
      for (OutputStream os : outputStreams) { 
       os.flush(); 
      } 
     } 

     public void close() throws IOException { 
      for (OutputStream os : outputStreams) { 
       os.close(); 
      } 
     } 
    } 
}

來源

2015-06-05 11:07:20

我怎麼能讀Java控制檯輸出到字符串緩衝區

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