org.apache.geode.internal.process.signal.AbstractSignalNotificationHandler.java Source code

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Here is the source code for org.apache.geode.internal.process.signal.AbstractSignalNotificationHandler.java

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/*
 * 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.geode.internal.process.signal;

import static org.apache.commons.lang.StringUtils.EMPTY;

import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * The AbstractSignalNotificationHandler class...
 *
 * @since GemFire 7.0
 */
public abstract class AbstractSignalNotificationHandler {

    /**
     * @deprecated use the enumerated type instead...
     */
    @Deprecated
    protected static final List<String> SIGNAL_NAMES;

    // Based on Open BSD OS Signals...
    static {
        String[] SIGNAL_NAMES_ARRAY = new String[] { EMPTY, "HUP", "INT", "QUIT", "ILL", "TRAP", "ABRT", "EMT",
                "FPE", "KILL", "BUS", "SEGV", "SYS", "PIPE", "ALRM", "TERM", "URG", "STOP", "TSTP", "CONT", "CHLD",
                "TTIN", "TTOU", "IO", "XCPU", "XFSZ", "VTALRM", "PROF", "WINCH", "INFO", "USR1", "USR2" };

        SIGNAL_NAMES = Collections.unmodifiableList(Arrays.asList(SIGNAL_NAMES_ARRAY));
    }

    private static final SignalListener LOGGING_SIGNAL_LISTENER = event -> System.out.printf(
            "Logging SignalListener Received Signal '%1$s' (%2$d)%n", event.getSignal().getName(),
            event.getSignal().getNumber());

    /**
     * Map used to register SignalListeners with SignalHandlers...
     */
    private final Map<Signal, Set<SignalListener>> signalListeners = Collections
            .synchronizedMap(new HashMap<Signal, Set<SignalListener>>(Signal.values().length));

    protected static void assertNotNull(final Object obj, final String message, final Object... arguments) {
        if (obj == null) {
            throw new NullPointerException(String.format(message, arguments));
        }
    }

    protected static void assertState(final boolean state, final String message, final Object... arguments) {
        if (!state) {
            throw new IllegalStateException(String.format(message, arguments));
        }
    }

    static void assertValidArgument(final boolean valid, final String message, final Object... arguments) {
        if (!valid) {
            throw new IllegalArgumentException(String.format(message, arguments));
        }
    }

    protected AbstractSignalNotificationHandler() {
        for (Signal signal : Signal.values()) {
            signalListeners.put(signal, Collections.synchronizedSet(new HashSet<>()));
        }
        // NOTE uncomment for debugging purposes...
        // debug();
    }

    boolean hasListeners(final Signal signal) {
        return !signalListeners.get(signal).isEmpty();
    }

    boolean isListening(final SignalListener listener) {
        boolean registered = false;

        for (Signal signal : Signal.values()) {
            registered |= isListening(listener, signal);
        }

        return registered;
    }

    boolean isListening(final SignalListener listener, final Signal signal) {
        assertNotNull(signal,
                "The signal to determine whether the listener is registered listening for cannot be null!");
        return signalListeners.get(signal).contains(listener);
    }

    protected void notifyListeners(final SignalEvent event) {
        Set<SignalListener> listeners = signalListeners.get(event.getSignal());
        Set<SignalListener> localListeners = Collections.emptySet();

        if (listeners != null) {
            synchronized (listeners) {
                localListeners = new HashSet<>(listeners);
            }
        }

        for (SignalListener listener : localListeners) {
            listener.handle(event);
        }
    }

    public boolean registerListener(final SignalListener listener) {
        assertNotNull(listener, "The SignalListener to register, listening for all signals cannot be null!");

        boolean registered = false;

        for (Signal signal : Signal.values()) {
            registered |= registerListener(listener, signal);
        }

        return registered;
    }

    boolean registerListener(final SignalListener listener, final Signal signal) {
        assertNotNull(signal, "The signal to register the listener for cannot be null!");
        assertNotNull(listener, "The SignalListener being registered to listen for '%1$s' signals cannot be null!",
                signal.getName());

        return signalListeners.get(signal).add(listener);
    }

    public boolean unregisterListener(final SignalListener listener) {
        boolean unregistered = false;

        for (Signal signal : Signal.values()) {
            unregistered |= unregisterListener(listener, signal);
        }

        return unregistered;
    }

    boolean unregisterListener(final SignalListener listener, final Signal signal) {
        assertNotNull(signal, "The signal from which to unregister the listener cannot be null!");

        return signalListeners.get(signal).remove(listener);
    }

    boolean unregisterListeners(final Signal signal) {
        assertNotNull(signal, "The signal from which to unregister all listeners cannot be null!");

        Set<SignalListener> listeners = signalListeners.get(signal);

        synchronized (listeners) {
            listeners.clear();
            return listeners.isEmpty();
        }
    }

    /**
     * Do not delete.
     */
    private void debug() {
        registerListener(LOGGING_SIGNAL_LISTENER);
    }
}