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the hasor DataBase project.
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/*
 * Copyright 2008-2009 the original author or authors.
 *
 * 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 net.hasor.db.datasource;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Savepoint;

/**
 *
 * @version : 2014-3-29
 * @author 赵永春 ([email protected])
 */
public class ConnectionHolder implements SavepointManager, ConnectionManager {
    private       int        referenceCount;
    private final DataSource dataSource;
    private       Connection connection;

    ConnectionHolder(final DataSource dataSource) {
        this.dataSource = dataSource;
    }

    public synchronized void requested() {
        this.referenceCount++;
    }

    public synchronized void released() throws SQLException {
        this.referenceCount--;
        if (!this.isOpen() && this.connection != null) {
            try {
                this.savepointCounter = 0;
                this.savepointSupported = null;
                this.connection.close();
            } finally {
                this.connection = null;
            }
        }
    }

    public synchronized Connection getConnection() throws SQLException {
        if (!this.isOpen()) {
            return null;
        }
        if (this.connection == null) {
            this.connection = this.dataSource.getConnection();
        }
        return this.connection;
    }

    public boolean isOpen() {
        return this.referenceCount != 0;
    }

    /**则表示当前数据库连接是否有被引用。*/
    public DataSource getDataSource() {
        return dataSource;
    }

    /**是否存在事务*/
    public boolean hasTransaction() throws SQLException {
        Connection conn = this.getConnection();
        if (conn == null) {
            return false;
        }
        //AutoCommit被标记为 false 表示开启了事务。
        return !conn.getAutoCommit();
    }

    /** 设置事务状态 */
    public void setTransaction() throws SQLException {
        Connection conn = this.getConnection();
        if (conn != null && conn.getAutoCommit()) {
            conn.setAutoCommit(false);
        }
    }

    /** 取消事务状态,设置为自动递交 */
    public void cancelTransaction() throws SQLException {
        Connection conn = this.getConnection();
        if (conn != null && !conn.getAutoCommit()) {
            conn.setAutoCommit(true);
        }
    }

    //---------------------------------------------------------------------------Savepoint
    private Connection checkConn(final Connection conn) throws SQLException {
        if (conn == null) {
            throw new SQLException("Connection is null.");
        }
        return conn;
    }

    private static final String  SAVEPOINT_NAME_PREFIX = "SAVEPOINT_";
    private              int     savepointCounter      = 0;
    private              Boolean savepointSupported;

    /**使用一个全新的名称创建一个保存点。*/
    @Override
    public Savepoint createSavepoint() throws SQLException {
        Connection conn = this.checkConn(this.getConnection());
        this.savepointCounter++;
        return conn.setSavepoint(ConnectionHolder.SAVEPOINT_NAME_PREFIX + this.savepointCounter);
    }

    @Override
    public void rollbackToSavepoint(final Savepoint savepoint) throws SQLException {
        Connection conn = this.checkConn(this.getConnection());
        conn.rollback(savepoint);
    }

    @Override
    public void releaseSavepoint(final Savepoint savepoint) throws SQLException {
        Connection conn = this.checkConn(this.getConnection());
        conn.releaseSavepoint(savepoint);
    }

    @Override
    public boolean supportSavepoint() throws SQLException {
        Connection conn = this.checkConn(this.getConnection());
        if (this.savepointSupported == null) {
            this.savepointSupported = conn.getMetaData().supportsSavepoints();
        }
        return this.savepointSupported;
    }
}