我怎么能读Java控制台输出到字符串缓冲区

17

好吧，这是一个有趣的问题。 Dosen似乎是一次解决所有PrintStream方法的优雅方式。（不幸的是没有FilterPrintStream）

我虽然写了一个丑陋的基于反射的解决方法（而不是在生产代码中使用我想:)

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; 
    } 
}

...可以像使用这样的：

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); 
    } 
}

结果输出：

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

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

（注寿呃，FilterOutputStream中的out字段是受保护和记录的，因此它是API的一部分:-)

来源

2010-12-02 13:28:25 aioobe

+1

哇！非常感谢。这个对我有用。 – Jacob 2010-12-03 05:49:28

5

一旦程序运行完毕，您就无法做到这一点。您需要在程序开始写入输出之前执行此操作。有关如何替换stdout和stderr的详细信息，请参阅this article。核心电话是System.setOut()和System.setErr()。

来源

2010-12-02 12:12:10 unwind

0

不要做之后，在第一个System.out.print()被调用之前创建两个StringBuilder对象，并将您想要保存的每个字符串追加到相应的StringBuilder。

来源

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

来源

2012-07-06 14:50:21 PeterVermont

0

这两行代码会将您的输出置于文本文件中，或者您可以根据需要更改目的地。

//创建一个文件： System.setOut（新的PrintStream（新FileOutputStream中（ “d：/MyOutputFile.txt”）））; //将输出重定向到文件： System.out.println（“Hello to custom output stream！”）;

希望其帮助你.. :)

来源

2013-03-17 08:17:11

0

这是一个实用工具类名为ConsoleOutputCapturer。它允许输出到现有控制台，但在场景后面继续捕获输出文本。您可以控制使用启动/停止方法捕获的内容。换句话说，调用start开始捕获控制台输出，一旦完成捕获，您可以调用stop方法，该方法返回一个String值，该值持有控制台输出，用于启动和停止调用之间的时间窗口。这个类虽然不是线程安全的。

 

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(); 
      } 
     } 
    } 
}

来源

2015-06-05 11:07:20

我怎么能读Java控制台输出到字符串缓冲区

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