java log4j 2 System.out.println turn off

Question

In My code:

System.out.println("hello println");
mylogger.info("hello info");
mylogger.debug("hello debug");

I want only log from logger in my console (no print "hello println" via System.out.println):

hello info

hello debug

My log4j file is:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j='http://jakarta.apache.org/log4j/'>

    <appender name="consoleInfo" class="org.apache.log4j.ConsoleAppender">
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="[%d{yyyy-MM-dd HH:mm:ss}]: %m%n" />
        </layout>
    </appender>

    <category name="org.openqa.selenium">
        <priority value="off" />
    </category>
    <category name="org.apache.log4j">
        <priority value="off" />
    </category>

    <root>
        <level value="INFO" />
        <appender-ref ref="consoleInfo" />
    </root>

</log4j:configuration>

Answer 1

You can "turn off" System.out by replacing it with a writer that just ignores all input:

System.out.println("This is written.");

System.setOut(new PrintStream(new OutputStream() {
    @Override
    public void write(int b) throws IOException {}
}));

System.out.println("Not written!");

If you happen to have Guava on the classpath, it can be shortened to

System.setOut(new PrintStream(ByteStreams.nullOutputStream()));

Answer 2

You can redirect your system outs to an appender by pointing the out parameter of System to an appender as below:

public abstract class TraceStream extends PrintStream
{
     private static final Logger trace =   LogManager.getLogger(TraceStream.class);
     public TraceStream(OutputStream stream) {
     super(stream);
     }

  protected abstract void trace(String line);


  public void print(boolean b) {
     TRACE.info(String.valueOf(b));
  }


  public void print(char c) {
    trace(String.valueOf(c));
  }


  public void print(char[] s) {
    trace(String.valueOf(s));
  }


  public void print(double d) {
     trace(String.valueOf(d));
  }


  public void print(float f) {
    trace(String.valueOf(f));
  }


  public void print(int i) {
    trace(String.valueOf(i));
  }


  public void print(long l) {
    trace(String.valueOf(l));
  }


  public void print(Object obj) {
    trace(obj.toString());
  }


  public void print(String s) {
    trace(s);
  }


  public void println() {
    trace("");
  }


  public void println(boolean x) {
    trace(String.valueOf(x));
  }


  public void println(char x) {
    trace(String.valueOf(x));
  }


  public void println(char[] x) {
    trace(String.valueOf(x));
  }


  public void println(double x) {
    trace(String.valueOf(x));
  }


  public void println(float x) {
    trace(String.valueOf(x));
  }


  public void println(int x) {
    trace(String.valueOf(x));
 }


 public void println(long x) {
   trace(String.valueOf(x));
 }


  public void println(Object x) {
   trace(x.toString());
  }


  public void println(String x) {
    trace(x);
  }


  public void write(int c) {
    trace(String.valueOf(c));
  }


  public static void traceStdErr() {
   System.setErr(new TraceStream(System.err) {
     protected void trace(String line) {
       TRACE.error(ThreeLetterCode.CODE_EXC, line);
     }
  });
}


 public static void traceStdOut() {
   System.setOut(new TraceStream(System.out) {
  protected void trace(String line) {
    TRACE.info(ThreeLetterCode.CODE_INF, line);
  }
   });
  }
}

This way , all your System outs and errs will reach the log file.