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The MongoDB Java Driver uber-artifact, containing the legacy driver, the mongodb-driver, mongodb-driver-core, and bson
There is a newer version: 3.12.14
/*
 * Copyright 2008-present MongoDB, 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 com.mongodb.binding;

import com.mongodb.ReadPreference;
import com.mongodb.async.SingleResultCallback;
import com.mongodb.connection.AsyncConnection;
import com.mongodb.connection.ServerDescription;
import com.mongodb.internal.connection.NoOpSessionContext;
import com.mongodb.session.SessionContext;

import static com.mongodb.assertions.Assertions.notNull;

/**
 * An asynchronous read binding that is bound to a single connection.
 *
 * @since 3.2
 */
public class AsyncSingleConnectionReadBinding extends AbstractReferenceCounted implements AsyncReadBinding {
    private final ReadPreference readPreference;
    private final ServerDescription serverDescription;
    private final AsyncConnection connection;

    /**
     * Construct an instance.
     *
     * @param readPreference the read preferenced of this binding
     * @param serverDescription the description of the server
     * @param connection the connection to bind to.
     */
    public AsyncSingleConnectionReadBinding(final ReadPreference readPreference, final ServerDescription serverDescription,
                                            final AsyncConnection connection) {
        this.readPreference = notNull("readPreference", readPreference);
        this.serverDescription = notNull("serverDescription", serverDescription);
        this.connection = notNull("connection", connection).retain();
    }

    @Override
    public ReadPreference getReadPreference() {
        return readPreference;
    }

    @Override
    public SessionContext getSessionContext() {
        return NoOpSessionContext.INSTANCE;
    }

    @Override
    public void getReadConnectionSource(final SingleResultCallback callback) {
          callback.onResult(new AsyncSingleConnectionSource(), null);
    }

    @Override
    public AsyncReadBinding retain() {
        super.retain();
        return this;
    }

    @Override
    public void release() {
        super.release();
        if (getCount() == 0) {
            connection.release();
        }
    }

    private class AsyncSingleConnectionSource extends AbstractReferenceCounted implements AsyncConnectionSource {
        AsyncSingleConnectionSource() {
            AsyncSingleConnectionReadBinding.this.retain();
        }

        @Override
        public ServerDescription getServerDescription() {
            return serverDescription;
        }

        @Override
        public SessionContext getSessionContext() {
            return NoOpSessionContext.INSTANCE;
        }

        @Override
        public void getConnection(final SingleResultCallback callback) {
            callback.onResult(connection.retain(), null);
        }

        @Override
        public AsyncConnectionSource retain() {
            super.retain();
            return this;
        }

        @Override
        public void release() {
            super.release();
            if (super.getCount() == 0) {
                AsyncSingleConnectionReadBinding.this.release();
            }
        }
    }
}