One logger for Android and for regular Java

Question

I have a common module which I'm developing in regular Java (PC) but also I want to use it in Android module.

How to log a message in PC module and see that message in Android log too?

Answer 1

You can use SLF4J API (which is lightweight facade of logging framework). I think it is the best way to develop libraries for Java.

You can read more about differences between SLF4J and log4j here.

For example, you can use the following code in your common module:

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Bar {

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

  public void foo(int value) {
    logger.info("entered Bar::foo value={}", value);
  }

}

After that you can use this code with one of SLF4J implementations:

• For non-Android module:
  • you can use LOGBack
  • or one of adapters: Log4jLoggerAdapter, JDK14LoggerAdapter, SimpleLogger, etc.
• For Android-module:
  • one of the simplest implementation Android Logger.
  • if you need some complex logging and you not so limited in application size logback-android is your choice.

Answer 2

use apache.log4j.Logger lib which easy to use for Log

Example

import org.apache.log4j.Logger;
    public class LoggerUtils {

        private static Logger log = null;

        // Static initializer loads only once when the class loads into memory
        static {
            System.out.println("Inside LoggerUtils static block");
            log = Logger.getLogger(LoggerUtils.class);
            System.out.println("LoggerUtils Class Name == "
                    + LoggerUtils.log.getClass().getName());
        }// end of static block

        /**
         * Default no argument constructor
         */
        public LoggerUtils() {
        }

        /**
         * @param String, debug statement to log.
         */
        public static void debug(String logString) {
            log.debug(logString);
        }

        /**
         * @param String, info statement to log.
         */
        public static void info(String logString) {
            log.info(logString);
        }

        /**
         * @param String, error statement to log.
         */
        public static void error(String logString) {
            log.error(logString);
        }

        /**
         * @param String, warning statement to log.
         */
        public static void warn(String logString) {
            log.warn(logString);
        }



        /**
         * @param logString, error message to log.
         * @param e, error object.
         */
        public static void error(String logString, Exception e) {

            error(logString);

            if (e != null) {

                StackTraceElement[] elements = null;
                elements = e.getStackTrace();

                if (elements != null) {
                    StringBuffer strBuffer = new StringBuffer("");
                    for (int i = 0; i < elements.length; i++) {
                        strBuffer.append(elements[i]).append("\n");
                    }

                    error("Stack Trace :: \n" + strBuffer.toString());
                    strBuffer = null;
                }

                elements = null;

            }// end of if(e != null)

        }

        /**
         * @param logString, error message to log.
         * @param messages, messageObject to log.
         */
        public static void error(String logString, Object[] messages) {
            error(logString);

            if (messages != null) {

                StringBuffer strBuffer = new StringBuffer("");
                for (int i = 0; i < messages.length; i++) {
                    strBuffer.append(messages[i]).append("\n");
                }
                error(strBuffer.toString());
                strBuffer = null;

            }// end of if(messages != null)

        }

        /**
         * @param logString, fatal message to log.
         */
        public static void fatal(String logString) {
            log.fatal(logString);
        }

    }// end of class - LoggerUtils

how to use in code

LoggerUtils.info(this.getClass().getName()+ ".name---> Entered");
LoggerUtils.error("Exception : "+ e);