Logger.java

package org.bndtools.api;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.Writer;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import org.eclipse.core.internal.runtime.InternalPlatform;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.osgi.framework.Bundle;
import org.osgi.framework.FrameworkUtil;

public class Logger implements ILogger {

    private static final Logger NULL_BUNDLE_LOGGER = new Logger(null);
    private static final Map<Bundle,Logger> CACHE = new HashMap<Bundle,Logger>();

    public synchronized static ILogger getLogger(Class< ? > clazz) {
        Bundle bundle = FrameworkUtil.getBundle(clazz);
        if (bundle == null)
            return NULL_BUNDLE_LOGGER;

        Logger result = CACHE.get(bundle);
        if (result != null)
            return result;

        result = new Logger(bundle);
        CACHE.put(bundle, result);
        return result;
    }

    private final Bundle bundle;

    private Logger(Bundle bundle) {
        this.bundle = bundle;
    }

    private String getStackTrace(Throwable t) {
        if (t == null) {
            return "No exception trace is available";
        }

        final Writer sw = new StringWriter();
        final PrintWriter pw = new PrintWriter(sw);
        t.printStackTrace(pw);
        return sw.toString();
    }

    private String constructSysErrString(IStatus status) {
        SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMdd HHmmss.SSS");
        String formattedDate = formatter.format(new Date());
        return String.format("%s - %s - %s - %s%n%s", formattedDate, status.getSeverity(), status.getPlugin(), status.getMessage(), getStackTrace(status.getException()));
    }

    private Status constructStatus(int status, String message, Throwable exception) {
        return new Status(status, bundle.getSymbolicName(), 0, message, exception);
    }

    private void log(int status, String message, Throwable exception) {
        logStatus(constructStatus(status, message, exception));
    }

    public void logError(String message, Throwable exception) {
        log(IStatus.ERROR, message, exception);
    }

    public void logWarning(String message, Throwable exception) {
        log(IStatus.WARNING, message, exception);
    }

    public void logInfo(String message, Throwable exception) {
        log(IStatus.INFO, message, exception);
    }

    public void logStatus(IStatus status) {
        if (bundle != null)
            InternalPlatform.getDefault().getLog(bundle).log(status);
        else
            System.err.println(constructSysErrString(status));
    }

}