LoggerFactory不能getLogger

Question

I'm currently implementing a Logger and I'm wondering why the code won't run. Most of the codes snipets are like these:

Logger log = LoggerFactory.getLogger(this.getClass());

My imported classes:

import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.service.log.LogReaderService;
import org.osgi.service.log.LogService;
import org.osgi.service.log.Logger;
import org.osgi.service.log.LoggerFactory;

But I can't seem to use getLogger.

Why is that?

Thanks in advance!

Answer 1

Here is the source code of org.osgi.service.log.LoggerFactory .

As you can see, it's an interface with no static methods therefore this code:

Logger log = LoggerFactory.getLogger(this.getClass());

is simply not valid.

To fix this use slf4j as front end (this means replace org.osgi.service.log.LoggerFactory import with org.slf4j.LoggerFactory etc.).

UPDATE

If you want to stick with org.osgi.service.log.LoggerFactory then follow this :

Obtain the LoggerFactory instance:

public class Activator implements BundleActivator
{
    private volatile LoggerFactory loggerFactory;

    public void start(BundleContext context) throws Exception 
    {   
        ServiceReference ref = context.getServiceReference(LoggerFactory.class.getName());
        if (ref != null)
        {
            loggerFactory = (LoggerFactory) context.getService(ref);
        }
    }

    //..

Elsewhere in the bundle you can then use the LoggerFactory to get a Logger for any class:

Logger logger = loggerFactory.getLogger(Foo.class);

UPDATE2

A better alternative would be to get a reference who's service type is LoggerFactory like this:

@Reference(service = LoggerFactory.class)
private Logger logger;

Answer 2

LoggerFactory is an OSGi service. You need to get it from the OSGi service registry. See my EclipseCon Europe 2018 presentation for more information.