JDBC編程學習筆記之數據庫連接池的實現

在JDBC編程的時候，獲取到一個數據庫連接資源是很寶貴的，倘若數據庫訪問量超大，而數據庫連接資源又沒能得到及時的釋放，就會導致系統的崩潰甚至宕機。造成的損失將會是巨大的。再看有了數據庫連接池的JDBC，就會較好的解決資源的創建與連接問題，其主要還是針對于連接資源使用層面的改進。下面我就談一談我對數據庫連接池的理解。

數據庫連接池理論基礎

對于創建一個數據庫連接池，需要做好準備工作。原理就是先實現DataSource接口，覆蓋里面的getConnection()方法，這個方法是我們最為關注的。既然是池，就不會是一個連接對象，因此需要使用集合來保存這些個連接對象。
但是，最為關鍵的是，開發人員在使用完連接對象后通常會調用conn.close(),方法來釋放數據庫連接資源，這將會把數據庫連接返還給數據庫，而不是數據庫連接池，因此，數據庫連接池的存在就沒了意義了。所以我們要增強close方法，來保證數據庫連接資源返還給數據庫連接池。

創建數據庫連接池

public class JDCBCPool implements DataSource {

    /*
     * 既然是一個數據庫連接池，就必須有許多的連接，所以需要使用一個集合類保存這些連接 (non-Javadoc)
     * 
     * @see javax.sql.CommonDataSource#getLogWriter()
     */
    private static  LinkedList<Connection> list = new LinkedList<Connection>();

    // 創建一個配置文件，用于讀取相應配置文件中保存的數據信息
    private static Properties config = new Properties();

    /*
     * 在這里向數據庫申請一批數據庫連接 為了只加載一次驅動程序，因此在靜態代碼塊中進行聲明，這樣驅動就只會加載一次
     */
    static {

        try {
            config.load(JDBCUtils.class.getClassLoader().getResourceAsStream("db.properties"));
            // Class.forName("com.mysql.jdbc.Driver");
            Class.forName(config.getProperty("DRIVER"));
            try {
                //申請十個數據庫連接對象，也就是數據庫連接池的容量是10
                for(int i=0 ;i<10;i++){
                    Connection conn =  DriverManager.getConnection(config.getProperty("URL"),
                            config.getProperty("USER"),config.getProperty("PASSWORD"));
                    list.add(conn);
                }
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        } catch (ClassNotFoundException | IOException e) {
            // TODO Auto-generated catch block
            throw new ExceptionInInitializerError();
        }
    }

    
    @Override
    public Connection getConnection() throws SQLException {
        
        if(list.size()<=0){
            throw new RuntimeException("數據庫忙，請待會再試試吧！");
        }
        //需要注意的是，不能使用get方式（這個方法知識返回一個引用而已）,
        //應該在獲取的同時，刪除掉這個鏈接，之后再還回來.現在注意是返還給數據庫連接池！！！
        Connection conn = list.removeFirst();
        MyConnection myconn = new MyConnection(conn);

        //從這里開始返回的就是一個數據庫連接池對象的conn
        return myconn;
    }

    
    
/////////////////////////////////////////////////////////////////////////datasource接口的實現方法開始    
    
    @Override
    public PrintWriter getLogWriter() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void setLogWriter(PrintWriter out) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public void setLoginTimeout(int seconds) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public int getLoginTimeout() throws SQLException {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }

    
    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }
}

不難看出，數據庫連接池相對于普通的數據庫連接的創建，并沒有什么特別難寫的部分。

增強close方法，保證數據庫連接資源用完后返還給連接池

要想增強close方法的功能，一般來說我們有如下幾種方式。

創建子類，覆蓋close方法，但是創建子類的時候要實現的部分可能會特別多，因此并不常用
使用包裝設計模式
使用動態代理方式

今天我就來實現一下怎么使用包裝設計模式來實現close方法的增強。

包裝設計模式實現close方法的增強

要實現包裝設計模式，思路很簡單。

創建一個類，實現與被增強對象相同的接口
將被增強對象作為一個成員變量加到這個類中
定義一個構造方法，并把被增強對象作為參數傳進來
覆蓋要增強的方法，這里是close方法
對于不想進行增強的方法，借助于被增強對象實現即可。

下面是基于包裝設計模式實現的增強的MyConnection類：

class MyConnection implements Connection {

        private Connection conn ;
        
        public MyConnection(Connection conn ){
            this.conn = conn;
        }
        
        /**
         * 自定義的包裝設計模式類，增強close方法，
         * 將數據庫鏈接資源返還給數據庫連接池，而不是數據庫
         */
        public void close(){
            list.add(conn);
        }

        @Override
        public <T> T unwrap(Class<T> iface) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.unwrap(iface);
        }

        @Override
        public boolean isWrapperFor(Class<?> iface) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.isWrapperFor(iface);
        }

        @Override
        public Statement createStatement() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createStatement();
        }

        @Override
        public PreparedStatement prepareStatement(String sql) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql);
        }

        @Override
        public CallableStatement prepareCall(String sql) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareCall(sql);
        }

        @Override
        public String nativeSQL(String sql) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.nativeSQL(sql);
        }

        @Override
        public void setAutoCommit(boolean autoCommit) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setAutoCommit(autoCommit);
        }

        @Override
        public boolean getAutoCommit() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getAutoCommit();
        }

        @Override
        public void commit() throws SQLException {
            // TODO Auto-generated method stub
            this.conn.commit();
        }

        @Override
        public void rollback() throws SQLException {
            // TODO Auto-generated method stub
            this.conn.rollback();
        }

        @Override
        public boolean isClosed() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.isClosed();
        }

        @Override
        public DatabaseMetaData getMetaData() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getMetaData();
        }

        @Override
        public void setReadOnly(boolean readOnly) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setReadOnly(readOnly);
        }

        @Override
        public boolean isReadOnly() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.isReadOnly();
        }

        @Override
        public void setCatalog(String catalog) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setCatalog(catalog);
        }

        @Override
        public String getCatalog() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getCatalog();
        }

        @Override
        public void setTransactionIsolation(int level) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setTransactionIsolation(level);
        }

        @Override
        public int getTransactionIsolation() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getTransactionIsolation();
        }

        @Override
        public SQLWarning getWarnings() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getWarnings();
        }

        @Override
        public void clearWarnings() throws SQLException {
            // TODO Auto-generated method stub
            this.conn.clearWarnings();
        }

        @Override
        public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createStatement(resultSetType, resultSetConcurrency);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency)
                throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, resultSetType, resultSetConcurrency);
        }

        @Override
        public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareCall(sql, resultSetType, resultSetConcurrency);
        }

        @Override
        public Map<String, Class<?>> getTypeMap() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getTypeMap();
        }

        @Override
        public void setTypeMap(Map<String, Class<?>> map) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setTypeMap(map);
        }

        @Override
        public void setHoldability(int holdability) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setHoldability(holdability);
        }

        @Override
        public int getHoldability() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getHoldability();
        }

        @Override
        public Savepoint setSavepoint() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.setSavepoint();
        }

        @Override
        public Savepoint setSavepoint(String name) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.setSavepoint(name);
        }

        @Override
        public void rollback(Savepoint savepoint) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.rollback(savepoint);
        }

        @Override
        public void releaseSavepoint(Savepoint savepoint) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.releaseSavepoint(savepoint);
        }

        @Override
        public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability)
                throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createStatement(resultSetType, resultSetConcurrency, resultSetHoldability);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency,
                int resultSetHoldability) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, resultSetType, resultSetConcurrency, resultSetHoldability);
        }

        @Override
        public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency,
                int resultSetHoldability) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareCall(sql, resultSetType, resultSetConcurrency, resultSetHoldability);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, autoGeneratedKeys);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, columnIndexes);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, columnNames);
        }

        @Override
        public Clob createClob() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createClob();
        }

        @Override
        public Blob createBlob() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createBlob();
        }

        @Override
        public NClob createNClob() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createNClob();
        }

        @Override
        public SQLXML createSQLXML() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createSQLXML();
        }

        @Override
        public boolean isValid(int timeout) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.isValid(timeout);
        }

        @Override
        public void setClientInfo(String name, String value) throws SQLClientInfoException {
            // TODO Auto-generated method stub
            this.conn.setClientInfo(name, value);
        }

        @Override
        public void setClientInfo(Properties properties) throws SQLClientInfoException {
            // TODO Auto-generated method stub
            this.conn.setClientInfo(properties);
        }

        @Override
        public String getClientInfo(String name) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getClientInfo(name);
        }

        @Override
        public Properties getClientInfo() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getClientInfo();
        }

        @Override
        public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createArrayOf(typeName, elements);
        }

        @Override
        public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createStruct(typeName, attributes);
        }

        @Override
        public void setSchema(String schema) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setSchema(schema);
        }

        @Override
        public String getSchema() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getSchema();
        }

        @Override
        public void abort(Executor executor) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.abort(executor);
        }

        @Override
        public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setNetworkTimeout(executor, milliseconds);
        }

        @Override
        public int getNetworkTimeout() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getNetworkTimeout();
        }
        
        
        
    }

一個簡單的數據庫連接池的實現案例

說是一個案例，其實也可以作為一個工具類作為今后程序開發的使用，這將會大大的提升數據庫連接資源的使用。需要注意的是，里面的驅動程序是基于我自己的數據庫來書寫的，進行使用時記得修改一下配置文件db.properties.文件中的內容即可。
db.properties中內容如下：

#when use this db.properties ,need to change the database name
DRIVER = com.mysql.jdbc.Driver
URL = jdbc:mysql://localhost:3306/test
USER = root
PASSWORD = mysql

下面就是JDBCPool工具類的實現：

package utils;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Array;
import java.sql.Blob;
import java.sql.CallableStatement;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.NClob;
import java.sql.PreparedStatement;
import java.sql.SQLClientInfoException;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.sql.SQLWarning;
import java.sql.SQLXML;
import java.sql.Savepoint;
import java.sql.Statement;
import java.sql.Struct;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;
import java.util.logging.Logger;

import javax.sql.DataSource;

/**
 * 數據庫連接池工具類
 * 
 * @author Summer
 *
 */
public class JDCBCPool implements DataSource {

    /*
     * 既然是一個數據庫連接池，就必須有許多的連接，所以需要使用一個集合類保存這些連接 (non-Javadoc)
     * 
     * @see javax.sql.CommonDataSource#getLogWriter()
     */
    private static  LinkedList<Connection> list = new LinkedList<Connection>();

    // 創建一個配置文件，用于讀取相應配置文件中保存的數據信息
    private static Properties config = new Properties();

    /*
     * 在這里向數據庫申請一批數據庫連接 為了只加載一次驅動程序，因此在靜態代碼塊中進行聲明，這樣驅動就只會加載一次
     */
    static {

        try {
            config.load(JDBCUtils.class.getClassLoader().getResourceAsStream("db.properties"));
            // Class.forName("com.mysql.jdbc.Driver");
            Class.forName(config.getProperty("DRIVER"));
            try {
                //申請十個數據庫連接對象，也就是數據庫連接池的容量是10
                for(int i=0 ;i<10;i++){
                    Connection conn =  DriverManager.getConnection(config.getProperty("URL"),
                            config.getProperty("USER"),config.getProperty("PASSWORD"));
                    list.add(conn);
                }
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        } catch (ClassNotFoundException | IOException e) {
            // TODO Auto-generated catch block
            throw new ExceptionInInitializerError();
        }
    }

    
    @Override
    public Connection getConnection() throws SQLException {
        
        if(list.size()<=0){
            throw new RuntimeException("數據庫忙，請待會再試試吧！");
        }
        //需要注意的是，不能使用get方式（這個方法知識返回一個引用而已）,
        //應該在獲取的同時，刪除掉這個鏈接，之后再還回來.現在注意是返還給數據庫連接池！！！
        Connection conn = list.removeFirst();
        MyConnection myconn = new MyConnection(conn);

        //從這里開始返回的就是一個數據庫連接池對象的conn
        return myconn;
    }

    
    
/////////////////////////////////////////////////////////////////////////datasource接口的實現方法開始    
    
    @Override
    public PrintWriter getLogWriter() throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void setLogWriter(PrintWriter out) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public void setLoginTimeout(int seconds) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public int getLoginTimeout() throws SQLException {
        // TODO Auto-generated method stub
        return 0;
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        // TODO Auto-generated method stub
        return false;
    }

    
    @Override
    public Connection getConnection(String username, String password) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }
/////////////////////////////////////////////////////////////////////////datasource接口的實現方法結束
    
    /**
     * 包裝設計模式實現流程：
     * 1.創建一個類，實現與被增強對象相同的接口
     * 2.將被增強對象當做自定義類的一個成員變量
     * 3.定義一個構造方法，將被增強對象傳遞進去
     * 4.增強想要增強的方法，進行覆蓋即可
     * 5.對于不像被增強的方法，調用被增強對象的方法進行處理即可
     * @author Summer
     *
     */
    
///////////////////////////////////////////////////////////////////////使用包裝設計模式，增強close方法的自定義類開始
    class MyConnection implements Connection {

        private Connection conn ;
        
        public MyConnection(Connection conn ){
            this.conn = conn;
        }
        
        /**
         * 自定義的包裝設計模式類，增強close方法，
         * 將數據庫鏈接資源返還給數據庫連接池，而不是數據庫
         */
        public void close(){
            list.add(conn);
        }

        @Override
        public <T> T unwrap(Class<T> iface) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.unwrap(iface);
        }

        @Override
        public boolean isWrapperFor(Class<?> iface) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.isWrapperFor(iface);
        }

        @Override
        public Statement createStatement() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createStatement();
        }

        @Override
        public PreparedStatement prepareStatement(String sql) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql);
        }

        @Override
        public CallableStatement prepareCall(String sql) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareCall(sql);
        }

        @Override
        public String nativeSQL(String sql) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.nativeSQL(sql);
        }

        @Override
        public void setAutoCommit(boolean autoCommit) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setAutoCommit(autoCommit);
        }

        @Override
        public boolean getAutoCommit() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getAutoCommit();
        }

        @Override
        public void commit() throws SQLException {
            // TODO Auto-generated method stub
            this.conn.commit();
        }

        @Override
        public void rollback() throws SQLException {
            // TODO Auto-generated method stub
            this.conn.rollback();
        }

        @Override
        public boolean isClosed() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.isClosed();
        }

        @Override
        public DatabaseMetaData getMetaData() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getMetaData();
        }

        @Override
        public void setReadOnly(boolean readOnly) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setReadOnly(readOnly);
        }

        @Override
        public boolean isReadOnly() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.isReadOnly();
        }

        @Override
        public void setCatalog(String catalog) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setCatalog(catalog);
        }

        @Override
        public String getCatalog() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getCatalog();
        }

        @Override
        public void setTransactionIsolation(int level) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setTransactionIsolation(level);
        }

        @Override
        public int getTransactionIsolation() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getTransactionIsolation();
        }

        @Override
        public SQLWarning getWarnings() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getWarnings();
        }

        @Override
        public void clearWarnings() throws SQLException {
            // TODO Auto-generated method stub
            this.conn.clearWarnings();
        }

        @Override
        public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createStatement(resultSetType, resultSetConcurrency);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency)
                throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, resultSetType, resultSetConcurrency);
        }

        @Override
        public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareCall(sql, resultSetType, resultSetConcurrency);
        }

        @Override
        public Map<String, Class<?>> getTypeMap() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getTypeMap();
        }

        @Override
        public void setTypeMap(Map<String, Class<?>> map) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setTypeMap(map);
        }

        @Override
        public void setHoldability(int holdability) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setHoldability(holdability);
        }

        @Override
        public int getHoldability() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getHoldability();
        }

        @Override
        public Savepoint setSavepoint() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.setSavepoint();
        }

        @Override
        public Savepoint setSavepoint(String name) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.setSavepoint(name);
        }

        @Override
        public void rollback(Savepoint savepoint) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.rollback(savepoint);
        }

        @Override
        public void releaseSavepoint(Savepoint savepoint) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.releaseSavepoint(savepoint);
        }

        @Override
        public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability)
                throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createStatement(resultSetType, resultSetConcurrency, resultSetHoldability);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency,
                int resultSetHoldability) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, resultSetType, resultSetConcurrency, resultSetHoldability);
        }

        @Override
        public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency,
                int resultSetHoldability) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareCall(sql, resultSetType, resultSetConcurrency, resultSetHoldability);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, autoGeneratedKeys);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, columnIndexes);
        }

        @Override
        public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.prepareStatement(sql, columnNames);
        }

        @Override
        public Clob createClob() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createClob();
        }

        @Override
        public Blob createBlob() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createBlob();
        }

        @Override
        public NClob createNClob() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createNClob();
        }

        @Override
        public SQLXML createSQLXML() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createSQLXML();
        }

        @Override
        public boolean isValid(int timeout) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.isValid(timeout);
        }

        @Override
        public void setClientInfo(String name, String value) throws SQLClientInfoException {
            // TODO Auto-generated method stub
            this.conn.setClientInfo(name, value);
        }

        @Override
        public void setClientInfo(Properties properties) throws SQLClientInfoException {
            // TODO Auto-generated method stub
            this.conn.setClientInfo(properties);
        }

        @Override
        public String getClientInfo(String name) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getClientInfo(name);
        }

        @Override
        public Properties getClientInfo() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getClientInfo();
        }

        @Override
        public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createArrayOf(typeName, elements);
        }

        @Override
        public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.createStruct(typeName, attributes);
        }

        @Override
        public void setSchema(String schema) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setSchema(schema);
        }

        @Override
        public String getSchema() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getSchema();
        }

        @Override
        public void abort(Executor executor) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.abort(executor);
        }

        @Override
        public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {
            // TODO Auto-generated method stub
            this.conn.setNetworkTimeout(executor, milliseconds);
        }

        @Override
        public int getNetworkTimeout() throws SQLException {
            // TODO Auto-generated method stub
            return this.conn.getNetworkTimeout();
        }
        
        
        
    }
/////////////////////////////////////////////////////////////////////////////包裝設計模式結束
}

總結

在實際的開發過程中，數據庫連接池使用的很廣泛，我們應該加以掌握。
數據庫連接對象應從數據庫連接池中獲取，使用完之后再返還給數據庫連接池
使用包裝設計模式進行方法的增強是較為合理的，但是更為常用的是開源的數據庫連接池，即動態代理方式。如DBCP等等

最后編輯于：2017.12.11 01:20:37

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