logback StatusListener的定义方法源码解读

/**
 * A StatusListener registered with logback context's {@link StatusManager} will
 * receive notification of every incoming {@link Status status} message.
 * 
 * @author Ceki Gülcü
 */
public interface StatusListener {
    void addStatusEvent(Status status);
}

public class NopStatusListener implements StatusListener {
    public void addStatusEvent(Status status) {
        // nothing to do
    }
}

abstract public class OnPrintStreamStatusListenerBase extends ContextAwareBase implements StatusListener, LifeCycle {
    boolean isStarted = false;
    static final long DEFAULT_RETROSPECTIVE = 300;
    long retrospectiveThresold = DEFAULT_RETROSPECTIVE;
    /**
     * The prefix to place before each status message
     * @since 1.1.10
     */
    String prefix;
    /**
     * The PrintStream used by derived classes
     * @return
     */
    abstract protected PrintStream getPrintStream();
    public void addStatusEvent(Status status) {
        if (!isStarted)
            return;
        print(status);
    }
    private void print(Status status) {
        StringBuilder sb = new StringBuilder();
        if(prefix != null)
            sb.append(prefix);
        StatusPrinter.buildStr(sb, "", status);
        getPrintStream().print(sb);
    }
    //......
}

/**
 * Print all new incoming status messages on the console (System.out).
 *
 * @author Ceki Gülcü
 */
public class OnConsoleStatusListener extends OnPrintStreamStatusListenerBase {
    @Override
    protected PrintStream getPrintStream() {
        return System.out;
    }
}

/**
 * Print all new incoming status messages on the error console (System.err).
 *
 * @author Ceki Gülcü
 * @since 1.0.8
 */
public class OnErrorConsoleStatusListener extends OnPrintStreamStatusListenerBase {
    @Override
    protected PrintStream getPrintStream() {
        return System.err;
    }
}

/**
 * Collect all incoming events in a list.
 * 
 * @author Ceki Gülcü
 * 
 */
public class StatusListenerAsList implements StatusListener {
    List<Status> statusList = new ArrayList<Status>();
    public void addStatusEvent(Status status) {
        statusList.add(status);
    }
    public List<Status> getStatusList() {
        return statusList;
    }
}