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Access to the Neo4j graph database through Java
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/*
 * Copyright (c) 2002-2016 "Neo Technology,"
 * Network Engine for Objects in Lund AB [http://neotechnology.com]
 *
 * This file is part of Neo4j.
 *
 * 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.neo4j.driver.internal;

import java.util.concurrent.atomic.AtomicBoolean;

import org.neo4j.driver.internal.security.SecurityPlan;
import org.neo4j.driver.v1.AccessMode;
import org.neo4j.driver.v1.Driver;
import org.neo4j.driver.v1.Logger;
import org.neo4j.driver.v1.Logging;
import org.neo4j.driver.v1.Session;

abstract class BaseDriver implements Driver
{
    private final static String DRIVER_LOG_NAME = "Driver";

    private final SecurityPlan securityPlan;
    protected final Logger log;

    private AtomicBoolean closed = new AtomicBoolean( false );

    BaseDriver( SecurityPlan securityPlan, Logging logging )
    {
        this.securityPlan = securityPlan;
        this.log = logging.getLog( DRIVER_LOG_NAME );
    }

    @Override
    public final boolean isEncrypted()
    {
        assertOpen();
        return securityPlan.requiresEncryption();
    }

    @Override
    public final Session session()
    {
        return session( AccessMode.WRITE );
    }

    @Override
    public final Session session( AccessMode mode )
    {
        assertOpen();
        Session session = newSessionWithMode( mode );
        if( closed.get() )
        {
            // the driver is already closed and we either 1. obtain this session from the old session pool
            // or 2. we obtain this session from a new session pool
            // For 1. this closeResources will take no effect as everything is already closed.
            // For 2. this closeResources will close the new connection pool just created to ensure no resource leak.
            closeResources();
            throw driverCloseException();
        }
        return session;
    }

    @Override
    public final void close()
    {
        if ( closed.compareAndSet(false, true) )
        {
            closeResources();
        }
    }

    protected abstract Session newSessionWithMode( AccessMode mode );

    protected abstract void closeResources();

    private void assertOpen()
    {
        if ( closed.get() )
        {
            throw driverCloseException();
        }
    }

    private IllegalStateException driverCloseException()
    {
        return new IllegalStateException( "This driver instance has already been closed" );
    }
}