How to add custom log handler to Google App Engine?

Question

I am trying to add a custom log handler to my java application. I have implemented a InnerLogger class that extends java.util.Logging.Handler class. And in my logging.properties declared as a handler:

handlers:com.mycompany.util.InnerLogger

But when I launch the development sever, I got the following error:

Can't load log handler "com.mycompany.util.InnerLogger"
java.lang.ClassNotFoundException: com.mycompany.util.InnerLogger

I can add my custom handler to loggers one by one ,but I just wondering is there a way to add it to all loggers.

Thanks

Related: [Issue 11499: Allow custom loggers for Java AppEngine](https://code.google.com/p/googleappengine/issues/detail?id=11499) — jmehrens, Sep 06 '16 at 16:57

score 3 · Accepted Answer · answered Jun 15 '12 at 00:58

3

I was able to add a Handler to the root Logger when my application initializes. You can put this code in a warmup task or servlet filter.

private static Logger LOG;

...

LOG = Logger.getLogger("");
LOG.addHandler(myCustomHandler);

Its not as graceful as using logging.properties, but it is an adequate workaround when running on GAE.

answered Jun 15 '12 at 00:58

Brad

5,428
1
33
56

This worked for me, although it ended up creating duplicate logging statements because I merely called LOG.addHandler(myCustomHandler). To fix that, you could remove the existing handlers returned from LOG.getHandlers(), and then add your custom handler. – sappenin Oct 16 '12 at 02:07
1

+1 Is the work-around still necessary as of GAE 1.9.1 and do we know the technical reason why the setting in logging.properties is ignored? – Drux Apr 30 '14 at 10:26

score 2 · Answer 2 · answered Apr 01 '12 at 23:08

2

It might not the solution you were looking for, but have you considered using Simple Logging Facade for Java (SLF4J) in your application instead of using directly JUL?

answered Apr 01 '12 at 23:08

Le Hibou

1,541
1
10
12

This is what I end up doing, using SLF4J with Log4J and a custom appender. – aimless Apr 03 '12 at 11:57

score 1 · Answer 3 · answered Feb 21 '13 at 16:22

    public static void addStreamHandler(){

    // TODO check if appCode has X length
    CustomHandler handler = new CustomHandler();
    LogManager manager = LogManager.getLogManager();
    Enumeration<String> e = manager.getLoggerNames();
    while (e.hasMoreElements()){

        Logger logger = manager.getLogger(e.nextElement());
        if ( logger.getName().startsWith("com.google"))continue;
        logger.addHandler(handler);
        System.out.println(logger.getName());
    }
    System.out.println("***finished*****");
}

public static void removeStreamHandlers(){

    LogManager manager = LogManager.getLogManager();
    Enumeration<String> e = manager.getLoggerNames();
    while (e.hasMoreElements()){

        Logger logger = manager.getLogger(e.nextElement());
        Handler[] handlers = logger.getHandlers();
        for ( int i = 0; i < handlers.length; i++){
            Handler h = handlers[i];
            if (h instanceof CustomHandler){
                logger.removeHandler(h);
                break;
            }
        }
    }
}

How to add custom log handler to Google App Engine?

3 Answers3

Linked