GetDataEventListener.java example

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/*
 * Copyright 2011 Google Inc.
 *
 * 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 org.bitcoinj.core.listeners;

import org.bitcoinj.core.*;

import javax.annotation.*;
import java.util.*;

/**
 * <p>Implementors can listen to events like blocks being downloaded/transactions being broadcast/connect/disconnects,
 * they can pre-filter messages before they are procesesed by a {@link Peer} or {@link PeerGroup}, and they can
 * provide transactions to remote peers when they ask for them.</p>
 */
public interface GetDataEventListener {

    /**
     * <p>Called when a peer receives a getdata message, usually in response to an "inv" being broadcast. Return as many
     * items as possible which appear in the {@link GetDataMessage}, or null if you're not interested in responding.</p>
     *
     * <p>Note that this will never be called if registered with any executor other than
     * {@link org.bitcoinj.utils.Threading#SAME_THREAD}</p>
     */
    @Nullable
    List<Message> getData(Peer peer, GetDataMessage m);
}