standardize python logger with JUL

Author: adamkorynta

regi-headless/src/main/java/usace/rowcps/headless/PythonJulHandler.java

@@ -0,0 +1,47 @@
+package usace.rowcps.headless;
+
+import java.util.logging.ErrorManager;
+import java.util.logging.Formatter;
+import java.util.logging.Handler;
+import java.util.logging.LogRecord;
+
+public final class PythonJulHandler extends Handler {
+    
+    private final PythonLogSink sink;
+    
+    private final Formatter messageFormatter = new Formatter() {
+        @Override
+        public String format(LogRecord record) {
+            return formatMessage(record);
+        }
+    };
+
+    public PythonJulHandler(PythonLogSink sink) {
+        this.sink = sink;
+    }
+
+    @Override
+    public void publish(LogRecord record) {
+        if (record == null || !isLoggable(record)) {
+            return;
+        }
+
+        try {
+            String message = messageFormatter.format(record);
+            sink.log(record, message);
+        } catch (RuntimeException ex) {
+            // Safeguard against failures in Python log handling.
+            reportError("Failed to publish JUL record to Python logging.", ex, ErrorManager.WRITE_FAILURE);
+        }
+    }
+
+    @Override
+    public void flush() {
+        // No-op. Python logging handlers manage their own flushing.
+    }
+
+    @Override
+    public void close() {
+        // No-op.
+    }
+}

regi-headless/src/main/java/usace/rowcps/headless/PythonLogSink.java

@@ -0,0 +1,7 @@
+package usace.rowcps.headless;
+
+import java.util.logging.LogRecord;
+
+public interface PythonLogSink {
+    void log(LogRecord record, String message);
+}

regi-headless/src/main/python/regi_python/regi_python.py

@@ -1,15 +1,8 @@
-#  Copyright (c) 2026
-#  United States Army Corps of Engineers - Hydrologic Engineering Center (USACE/HEC)
-#  All Rights Reserved.  USACE PROPRIETARY/CONFIDENTIAL.
-#  Source may not be released without written approval from HEC
-
 import os
-import logging
 import jpype
 import jpype.imports
 from contextlib import contextmanager
-from pathlib import Path
-from .regi_python_logging import configure_logging
+from .regi_python_logging import configure_logging, configure_jul_to_python_logging
 
 logger = configure_logging()
 
@@ -35,6 +28,7 @@ def regi_session():
             convertStrings=True,
             classpath=[LIB_PATH]
         )
+        configure_jul_to_python_logging(logger)
 
     try:
         yield

regi-headless/src/main/python/regi_python/regi_python_logging.py

@@ -1,10 +1,8 @@
-#  Copyright (c) 2026
-#  United States Army Corps of Engineers - Hydrologic Engineering Center (USACE/HEC)
-#  All Rights Reserved.  USACE PROPRIETARY/CONFIDENTIAL.
-#  Source may not be released without written approval from HEC
-
-import logging
 import os
+import logging
+from jpype import JImplements, JOverride
+
+_java_log_sink = None
 
 
 def _get_log_level():
@@ -15,6 +13,7 @@ def _get_log_level():
         log_level = logging.INFO
     return log_level, invalid_log_level, log_level_name
 
+
 def configure_logging():
     log_level, invalid_log_level, log_level_name = _get_log_level()
 
@@ -44,4 +43,71 @@ def filter(self, record):
     if invalid_log_level:
         logger.warning("Invalid REGI_LOG_LEVEL '%s'; using INFO.", log_level_name)
 
-    return logger
+    return logger
+
+
+def configure_jul_to_python_logging(python_logger):
+    global _java_log_sink
+
+    from java.util.logging import Logger, Level
+    from usace.rowcps.headless import PythonJulHandler
+
+    java_level = _python_level_to_jul_level(python_logger.getEffectiveLevel())
+
+    root_logger = Logger.getLogger("")
+    root_logger.setLevel(java_level)
+
+    for handler in root_logger.getHandlers():
+        root_logger.removeHandler(handler)
+
+    _java_log_sink = PythonLogSink(python_logger)
+
+    handler = PythonJulHandler(_java_log_sink)
+    handler.setLevel(java_level)
+
+    root_logger.addHandler(handler)
+    
+
+def _python_level_to_jul_level(python_level):
+    from java.util.logging import Level
+
+    if python_level <= logging.DEBUG:
+        return Level.FINE
+    if python_level <= logging.INFO:
+        return Level.INFO
+    if python_level <= logging.WARNING:
+        return Level.WARNING
+    if python_level <= logging.ERROR:
+        return Level.SEVERE
+    return Level.OFF
+
+
+def _jul_level_to_python_level(jul_level_name):
+    mapping = {
+        "SEVERE": logging.ERROR,
+        "WARNING": logging.WARNING,
+        "INFO": logging.INFO,
+        "CONFIG": logging.INFO,
+        "FINE": logging.DEBUG,
+        "FINER": logging.DEBUG,
+        "FINEST": logging.DEBUG,
+    }
+    return mapping.get(str(jul_level_name), logging.INFO)
+
+
+@JImplements("usace.rowcps.headless.PythonLogSink")
+class PythonLogSink:
+    def __init__(self, python_logger):
+        self._logger = python_logger
+
+    @JOverride
+    def log(self, record, message):
+        level = _jul_level_to_python_level(record.getLevel().getName())
+        name = str(record.getLoggerName() or "java")
+        message = str(message)
+
+        thrown = record.getThrown()
+        if thrown is not None:
+            message = f"{message}\n{thrown}"
+
+        self._logger.log(level, "[%s] %s", name, message)