EventTailCommand.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.karaf.event.command;

import static org.apache.karaf.event.service.TopicPredicate.matchTopic;

import java.util.function.Consumer;
import java.util.function.Predicate;

import org.apache.karaf.event.service.EventCollector;
import org.apache.karaf.shell.api.action.Action;
import org.apache.karaf.shell.api.action.Argument;
import org.apache.karaf.shell.api.action.Command;
import org.apache.karaf.shell.api.action.Option;
import org.apache.karaf.shell.api.action.lifecycle.Reference;
import org.apache.karaf.shell.api.action.lifecycle.Service;
import org.apache.karaf.shell.api.console.Session;
import org.osgi.framework.BundleContext;
import org.osgi.service.event.Event;

@Command(scope = "event", name = "tail", description = "Shows events and listens for incoming events")
@Service
public class EventTailCommand implements Action {

    @Reference
    Session session;

    @Reference
    BundleContext context;

    @Reference
    EventCollector collector;

    @Argument
    String topicFilter = "*";

    @Option(name = "-v")
    boolean verbose = false;

    @Override
    public Object execute() throws Exception {
        EventPrinter printer = new EventPrinter(session.getConsole(), verbose);
        Consumer<Event> filteredPrinter = executeIf(matchTopic(topicFilter), printer);
        collector.addConsumer(filteredPrinter);
        try {
            waitTillInterrupted();
        } catch (InterruptedException e) {
            collector.removeConsumer(filteredPrinter);
        }
        return null;
    }
    
    private <T> Consumer<T> executeIf(Predicate<T> pred, Consumer<T> consumer) {
        return t -> {if (pred.test(t)) consumer.accept(t);};
    }

    private void waitTillInterrupted() throws InterruptedException {
        while (true) {
            Thread.sleep(100);
        }
    }
}