将System.out.println重定向到Log4J，同时保留类名信息 [英] Redirect System.out.println to Log4J, while keeping class name information

问题描述

我有一些库在我身上调用System.out.println，我想通过log4j或commons日志记录重定向它们。但特别是我想保留完全限定的类名，所以我知道哪个组件生成了日志。

I have some libraries that are calling System.out.println on me, I'd like to redirect them through log4j or commons logging. But in particular I'd like to keep the fully-qualified-classname so I know what component generated the logs.

有没有一个很好的，有序的方法来完成这个？

Is there a nice, orderly way to accomplish this?

更新：完成此操作后，我在此处发布了代码：


http://www.bukisa.com/articles/487009_java-how-to-redirect-stderr-and-stdout-to-commons-logging-with-the-calling-class

推荐答案

我能想到的唯一方法就是编写自己的 PrintStream 在调用 println 方法时创建堆栈跟踪的实现，以便计算出类名。这将是相当可怕的，但它应该工作...概念证明示例代码：

The only way I can think of would be to write your own PrintStream implementation which created a stack trace when the println method was called, in order to work out the class name. It would be pretty horrible, but it should work... proof of concept sample code:

import java.io.*;

class TracingPrintStream extends PrintStream {
  public TracingPrintStream(PrintStream original) {
    super(original);
  }

  // You'd want to override other methods too, of course.
  @Override
  public void println(String line) {
    StackTraceElement[] stack = Thread.currentThread().getStackTrace();
    // Element 0 is getStackTrace
    // Element 1 is println
    // Element 2 is the caller
    StackTraceElement caller = stack[2];
    super.println(caller.getClassName() + ": " + line);
  }
}

public class Test {
  public static void main(String[] args) throws Exception {
    System.setOut(new TracingPrintStream(System.out));
    System.out.println("Sample line");
  }
}

（在你的代码中你可以登录到log4j而不是当然......或者可能也是如此。）

(In your code you would make it log to log4j instead of course... or possibly as well.)

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