#3374, #3389: Improve log handling of normal java.util Logger usage by forwarding the LogRecords directly to the BungeeLogger instead of the fallback err stream.

log/src/main/java/net/md_5/bungee/log/BungeeLogger.java

@@ -24,6 +24,7 @@ public class BungeeLogger extends Logger
     {
         super( loggerName, null );
         setLevel( Level.ALL );
+        setUseParentHandlers( false );
 
         try
         {

log/src/main/java/net/md_5/bungee/log/LoggingForwardHandler.java

@@ -0,0 +1,29 @@
+package net.md_5.bungee.log;
+
+import java.util.logging.Handler;
+import java.util.logging.LogRecord;
+import java.util.logging.Logger;
+import lombok.RequiredArgsConstructor;
+
+@RequiredArgsConstructor
+public class LoggingForwardHandler extends Handler
+{
+
+    private final Logger logger;
+
+    @Override
+    public void publish(LogRecord record)
+    {
+        logger.log( record );
+    }
+
+    @Override
+    public void flush()
+    {
+    }
+
+    @Override
+    public void close() throws SecurityException
+    {
+    }
+}

proxy/src/main/java/net/md_5/bungee/BungeeCord.java

@@ -87,6 +87,7 @@ import net.md_5.bungee.conf.Configuration;
 import net.md_5.bungee.conf.YamlConfig;
 import net.md_5.bungee.forge.ForgeConstants;
 import net.md_5.bungee.log.BungeeLogger;
+import net.md_5.bungee.log.LoggingForwardHandler;
 import net.md_5.bungee.log.LoggingOutputStream;
 import net.md_5.bungee.module.ModuleManager;
 import net.md_5.bungee.netty.PipelineUtils;
@@ -209,6 +210,21 @@ public class BungeeCord extends ProxyServer
 
         logger = new BungeeLogger( "BungeeCord", "proxy.log", consoleReader );
         JDK14LoggerFactory.LOGGER = logger;
+
+        // Before we can set the Err and Out streams to our LoggingOutputStream we also have to remove
+        // the default ConsoleHandler from the root logger, which writes to the err stream.
+        // But we still want to log these records, so we add our own handler which forwards the LogRecord to the BungeeLogger.
+        // This way we skip the err stream and the problem of only getting a string without context, and can handle the LogRecord itself.
+        // Thus improving the default bahavior for projects that log on other Logger instances not created by BungeeCord.
+        Logger rootLogger = Logger.getLogger( "" );
+        for ( Handler handler : rootLogger.getHandlers() )
+        {
+            rootLogger.removeHandler( handler );
+        }
+        rootLogger.addHandler( new LoggingForwardHandler( logger ) );
+
+        // We want everything that reaches these output streams to be handled by our logger
+        // since it applies a nice looking format and also writes to the logfile.
         System.setErr( new PrintStream( new LoggingOutputStream( logger, Level.SEVERE ), true ) );
         System.setOut( new PrintStream( new LoggingOutputStream( logger, Level.INFO ), true ) );