How to Enable Mapped Diagnostic Context (MDC) Support for Java Util Logging (JUL)?

How can I enable Mapped Diagnostic Context (MDC) support for Java Util Logging (JUL)?

import java.util.logging.*;
import org.slf4j.MDC; // Assuming you are using SLF4J for MDC

// Example of setting and getting MDC
MDC.put("userId", "12345");
LOGGER.info("This log is related to user: " + MDC.get("userId"));
MDC.clear();

Mapped Diagnostic Context (MDC) is a powerful feature for enhancing log messages in Java applications, providing context-specific information. Integrating MDC with Java Util Logging (JUL) allows for enriching your logs with contextual details, making them more informative and easier to troubleshoot.

import java.util.logging.*;
import org.slf4j.MDC;

public class MdcFormatter extends Formatter {
    @Override
    public String format(LogRecord record) {
        String mdcData = MDC.get("someKey");  // Retrieve MDC value
        return String.format("[%s] %s: %s - %s\n", 
            record.getMillis(),
            record.getLevel(),
            mdcData,
            record.getMessage());
    }
}

Causes

• JUL does not natively support MDC without an additional implementation.
• Lack of proper thread context management when using JUL.

Solutions

• Use an adapter library to bridge SLF4J's MDC with JUL, such as 'slf4j-jdk14' or logback that supports JUL logging.
• Set up a custom Formatter in JUL to include MDC context in the log output. Here's how to do it:
• 1. Implement a custom Formatter that retrieves MDC values. 2. Configure your Logger to use this Formatter for better output.

Mistake: Not clearing MDC values after logging, leading to leakage of context information between requests.

Solution: Make sure to call MDC.clear() after logging to prevent context leakage.

Mistake: Assuming that MDC values persist across threads without proper context management.

Solution: Use thread-local storage or ensure proper context propagation when using MDC in multi-threaded environments.