Question

我有一个使用log4j的java应用程序。

配置：

log4j.rootLogger=info, file

log4j.appender.file=org.apache.log4j.DailyRollingFileAppender
log4j.appender.file.File=${user.home}/logs/app.log
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d [%t] %c %p %m%n

因此所有日志语句都正确地附加到文件中，但我丢失了stdout和stderr。如何将异常堆栈跟踪和sysout重定向到每日滚动文件？

Answer 1

// I set up a ConsoleAppender in Log4J to format Stdout/Stderr
log4j.rootLogger=DEBUG, CONSOLE
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=[%t] %-5p %c - %m%n


// And I call this StdOutErrLog.tieSystemOutAndErrToLog() on startup

public class StdOutErrLog {

    private static final Logger logger = Logger.getLogger(StdOutErrLog.class);

    public static void tieSystemOutAndErrToLog() {
        System.setOut(createLoggingProxy(System.out));
        System.setErr(createLoggingProxy(System.err));
    }

    public static PrintStream createLoggingProxy(final PrintStream realPrintStream) {
        return new PrintStream(realPrintStream) {
            public void print(final String string) {
                realPrintStream.print(string);
                logger.info(string);
            }
        };
    }
}

Answer 2

在Skaffman代码中：要删除log4j日志中的空行，只需将“println”方法添加到createLoggingProxy的PrintStream

public static PrintStream createLoggingProxy(final PrintStream realPrintStream) {
    return new PrintStream(realPrintStream) {
        public void print(final String string) {
            logger.warn(string);
        }
        public void println(final String string) {
            logger.warn(string);
        }
    };
}

Answer 3

我从迈克尔·S那里得到了这个想法，但是就像在一条评论中提到的那样，它有一些问题：它没有捕获所有内容，而是打印出一些空行。

此外，我想将System.out和System.err分开，以便System.out记录日志级别'INFO'，并System.err记录'ERROR' （或'WARN'如果你愿意的话）。

所以这是我的解决方案：首先是一个扩展OutputStream的类（更容易覆盖OutputStream的所有方法而不是PrintStream）。它以指定的日志级别记录，并将所有内容复制到另一个OutputStream。并且它还检测“空”字符串（仅包含空格）并且不记录它们。

import java.io.IOException;
import java.io.OutputStream;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

public class LoggerStream extends OutputStream
{
private final Logger logger;
private final Level logLevel;
private final OutputStream outputStream;

public LoggerStream(Logger logger, Level logLevel, OutputStream outputStream)
{
    super();

    this.logger = logger;
    this.logLevel = logLevel;
    this.outputStream = outputStream;
}

@Override
public void write(byte[] b) throws IOException
{
    outputStream.write(b);
    String string = new String(b);
    if (!string.trim().isEmpty())
        logger.log(logLevel, string);
}

@Override
public void write(byte[] b, int off, int len) throws IOException
{
    outputStream.write(b, off, len);
    String string = new String(b, off, len);
    if (!string.trim().isEmpty())
        logger.log(logLevel, string);
}

@Override
public void write(int b) throws IOException
{
    outputStream.write(b);
    String string = String.valueOf((char) b);
    if (!string.trim().isEmpty())
        logger.log(logLevel, string);
}
}

然后是一个非常简单的实用工具类来设置out和err：

import java.io.PrintStream;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

public class OutErrLogger
{
public static void setOutAndErrToLog()
{
    setOutToLog();
    setErrToLog();
}

public static void setOutToLog()
{
    System.setOut(new PrintStream(new LoggerStream(Logger.getLogger("out"), Level.INFO, System.out)));
}

public static void setErrToLog()
{
    System.setErr(new PrintStream(new LoggerStream(Logger.getLogger("err"), Level.ERROR, System.err)));
}

}

Answer 4

如果您使用的是应用程序服务器，servlet容器或类似内容，请参阅kgiannakakis's answer。

对于独立应用，请参阅this。您可以使用stdin课程重新定位stdout，stderr和java.lang.System。基本上，您创建了一个新的PrintStream子类，并将该实例设置为System.out。

应用程序启动时的这些内容（未经测试）。

// PrintStream object that prints stuff to log4j logger
public class Log4jStream extends PrintStream {
      public void write(byte buf[], int off, int len) {
        try {
           // write stuff to Log4J logger
        } catch (Exception e) {
       }
    }
}

// reassign standard output to go to log4j
System.setOut(new Log4jStream());

Answer 5

上面的答案为使用代理进行STDOUT / ERR日志记录提供了一个很好的主意。但是，提供的实现示例对于所有情况都不能很好地工作。例如，尝试

System.out.printf（＆＃34;测试％s \ n＆＃34;，＆＃34; ABC＆＃34;）;

上面示例中的代码会将输出切换为控制台和多个不可读的Log4j条目中的单独部分。

解决方案是缓冲输出，直到触发＆＃39; \ n＆＃39;在缓冲区结束时找到。有时缓冲区以＆＃39; \ r \ n \ n＆＃39;结尾。下面的课程解决了这个问题。它功能齐全。调用静态方法bind（）来激活它。

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

// Based on
// http://stackoverflow.com/questions/1200175/log4j-redirect-stdout-to-dailyrollingfileappender
public class Log4jStdOutErrProxy {

  public static void bind() {
    bind(Logger.getLogger("STDOUT"), Logger.getLogger("STDERR"));
  }

  @SuppressWarnings("resource")
  public static void bind(Logger loggerOut, Logger loggerErr) {
    System.setOut(new PrintStream(new LoggerStream(loggerOut, Level.INFO,  System.out), true));
    System.setErr(new PrintStream(new LoggerStream(loggerErr, Level.ERROR, System.err), true));
  }

  private static class LoggerStream extends OutputStream {
    private final Logger logger;
    private final Level logLevel;
    private final OutputStream outputStream;
    private StringBuilder sbBuffer;

    public LoggerStream(Logger logger, Level logLevel, OutputStream outputStream) {
      this.logger = logger;
      this.logLevel = logLevel;
      this.outputStream = outputStream;
      sbBuffer = new StringBuilder();
    }

    @Override
    public void write(byte[] b) throws IOException {
      doWrite(new String(b));
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
      doWrite(new String(b, off, len));
    }

    @Override
    public void write(int b) throws IOException {
      doWrite(String.valueOf((char)b));
    }

    private void doWrite(String str) throws IOException {
      sbBuffer.append(str);
      if (sbBuffer.charAt(sbBuffer.length() - 1) == '\n') {
        // The output is ready
        sbBuffer.setLength(sbBuffer.length() - 1); // remove '\n'
        if (sbBuffer.charAt(sbBuffer.length() - 1) == '\r') {
          sbBuffer.setLength(sbBuffer.length() - 1); // remove '\r'
        }
        String buf = sbBuffer.toString();
        sbBuffer.setLength(0);
        outputStream.write(buf.getBytes());
        outputStream.write('\n');
        logger.log(logLevel, buf);
      }
    }
  } // inner class LoggerStream  

}

Answer 6

我认为你是通过e.printStackTrace()记录堆栈跟踪的？您可以将异常对象传递给Log4j日志记录方法，这些方法将显示在您的日志中（请参阅Logger.error(Object obj, Throwable t)）

请注意，您可以将System.out和System.err更改为重定向到Log4j的另一个PrintStream。这将是一个简单的更改，并保存您转换所有System.out.println()语句。

Answer 7

从容器管理标准输出和错误流。例如，Tomcat使用JULI记录输出和错误流。

我的建议是保留原样。避免在应用程序中使用System.out.print。有关堆栈跟踪，请参阅here。

Answer 8

@迈克尔的缩影是一个好点。但扩展PrintStream并不是很好，因为它使用内部方法void write(String)将所有内容写入OutputStream。

我更喜欢使用Log4J Contrib软件包中的LoggingOutputStream Class。

然后我像这样重定向系统流：

public class SysStreamsLogger {
    private static Logger sysOutLogger = Logger.getLogger("SYSOUT");
    private static Logger sysErrLogger = Logger.getLogger("SYSERR");

    public static final PrintStream sysout = System.out;
    public static final PrintStream syserr = System.err;

    public static void bindSystemStreams() {
        // Enable autoflush
        System.setOut(new PrintStream(new LoggingOutputStream(sysOutLogger, LogLevel.INFO), true));
        System.setErr(new PrintStream(new LoggingOutputStream(sysErrLogger, LogLevel.ERROR), true));
    }

    public static void unbindSystemStreams() {
        System.setOut(sysout);
        System.setErr(syserr);
    }
}

Answer 9

在使用System.setOut和System.setErr方法之前，我们应该使用reset（）方法重置java.util.logging.LogManager对象。

public static void tieSystemOutAndErrToLog() {

    try{

        // initialize logging to go to rolling log file
        LogManager logManager = LogManager.getLogManager();
        logManager.reset();

        // and output on the original stdout
        System.out.println("Hello on old stdout");
        System.setOut(createLoggingProxy(System.out));
        System.setErr(createLoggingProxy(System.err));

        //Following is to make sure whether system.out and system.err is redirecting to the stdlog.log file
        System.out.println("Hello world!");

        try {
            throw new RuntimeException("Test");
        } catch (Exception e) {
            e.printStackTrace();
        }

    }catch(Exception e){
        logger.error("Caught exception at StdOutErrLog ",e);
        e.printStackTrace();
    }
}

Answer 10

对于那些希望在log4j2中做到这一点的人。现在有一个组件可以为您创建这些流。

需要包括log4j-iostreams jar
参见：https://logging.apache.org/log4j/2.x/log4j-iostreams/index.html

示例：


def createPlayers():
        players = []
        player1Name = input("Please enter the first players name: ")
        player1 = Player(player1Name)
        players.append(player1)

        player2Name = input("Please enter the second players name: ")
        player2 = Player(player2Name)
        players.append(player2)

        print(players)    
        if numberOfPlayers == 3:
            player3Name = input("Please enter the third players name: ")
            player3 = Player(player3Name)

            players.append(player3)

        elif numberOfPlayers == 4:
            player3Name = input("Please enter the third players name: ")
            player3 = Player(player3Name)

            players.append(player3)
            player4Name = input("Please enter the fourth players name: ")
            player4 = Player(player4Name)

            players.append(player4)

        else:
            print("Please pick between 2 and 4 players.")


def drawGrid():
    window.blit(boardImage,(0,0))
    for x in range (height):
        for y in range(width)::
                if board[x][y] == player1.Pos:
                    pygame.draw.circle(window, PlayerOneColour, (x * squareSize + int(squareSize/2) -10, y*squareSize +int(squareSize/2)+6) ,charSize)
                if board[x][y] == player2.Pos:
                    pygame.draw.circle(window, PlayerTwoColour, (x * squareSize + int(squareSize/2) +10, y*squareSize +int(squareSize/2)+6) ,charSize)
                if numberOfPlayers == 3:
                    if board[x][y] == player3.Pos:
                        pygame.draw.circle(window, PlayerThreeColour, (x * squareSize + int(squareSize/2) +10, y*squareSize +int(squareSize/2)+6) ,charSize)
                if numberOfPlayers == 4:
                    if board[x][y] == player4.Pos:
                        pygame.draw.circle(window, PlayerFourColour, (x * squareSize + int(squareSize/2) +10, y*squareSize +int(squareSize/2)+6) ,charSize)

log4j将stdout重定向到DailyRollingFileAppender

10 个答案: