jflowmap.util.Log4ExportAppender.java Source code

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Here is the source code for jflowmap.util.Log4ExportAppender.java

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/*
 * This file is part of JFlowMap.
 *
 * Copyright 2009 Ilya Boyandin
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package jflowmap.util;

import java.util.LinkedList;

import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.Logger;
import org.apache.log4j.PatternLayout;
import org.apache.log4j.spi.ErrorCode;
import org.apache.log4j.spi.LoggingEvent;

import com.google.common.base.Function;
import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;

/**
 * @author Ilya Boyandin
 */
public class Log4ExportAppender extends AppenderSkeleton {

    private long maxNumOfMessages = 1000000;
    private final LinkedList<Pair<Long, String>> messageEvents = Lists.newLinkedList();

    public Log4ExportAppender() {
        setLayout(new PatternLayout("%d{HH:mm.ss,SSS} %-5p - %m%n"));
    }

    public static Log4ExportAppender createAndSetup() {
        Log4ExportAppender app = new Log4ExportAppender();
        setup(app);
        return app;
    }

    public static void setup(Log4ExportAppender app) {
        Logger rootLogger = Logger.getRootLogger();
        rootLogger.addAppender(app);
    }

    /**
     * @param timestamp The number of milliseconds elapsed from 1/1/1970.
     */
    public Iterable<String> getMessagesAfter(final long timestamp) {
        return messagesOf(Iterables.filter(messageEvents, new Predicate<Pair<Long, String>>() {
            @Override
            public boolean apply(Pair<Long, String> input) {
                return input.first() > timestamp;
            }
        }));
    }

    public Iterable<String> getMessages() {
        return messagesOf(messageEvents);
    }

    public static Iterable<String> messagesOf(Iterable<Pair<Long, String>> messages) {
        return Iterables.transform(messages, new Function<Pair<Long, String>, String>() {
            @Override
            public String apply(Pair<Long, String> from) {
                return from.second();
            }
        });
    }

    @Override
    protected void append(LoggingEvent ev) {
        if (layout == null) {
            errorHandler.error("No layout for appender " + name, null, ErrorCode.MISSING_LAYOUT);
            return;
        }

        addMessage(ev.timeStamp, layout.format(ev));

        // Boilerplate code: handle exceptions if not handled by layout object
        if (layout.ignoresThrowable()) {
            String[] messages = ev.getThrowableStrRep();
            if (messages != null) {
                for (String msg : messages) {
                    addMessage(ev.timeStamp, msg);
                }
            }
        }
    }

    private void addMessage(long timestamp, String msg) {
        messageEvents.add(Pair.of(timestamp, msg));
        applySizeRestriction();
    }

    private void applySizeRestriction() {
        while (!messageEvents.isEmpty() && messageEvents.size() > maxNumOfMessages) {
            messageEvents.remove();
        }
    }

    public void setMaxNumOfMessages(long maxNumOfMessages) {
        this.maxNumOfMessages = maxNumOfMessages;
        applySizeRestriction();
    }

    @Override
    public void close() {
    }

    @Override
    public boolean requiresLayout() {
        return false;
    }

}