使用装饰着设计模式开发自定义jdbc连接池

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1.数据库配置文件db.properties

driver=com.mysql.jdbc.Driverurl=jdbc:mysql://localhost:3306/web08?useUnicode=true&characterEncoding=utf8username=rootpassword=root

2:获取连接和释放资源的方法

package cn.itheima.jdbc.utils;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import java.util.Properties;import java.util.ResourceBundle;/** * 获取连接和释放资源的方法 * @author Administrator * */public class JDBCUtils_V3 {    private static String driver;    private static String url;    private static String username;    private static String password;    static{        try {            //通过类加载器的方法获得文件输入流            InputStream in = JDBCUtils_V3.class.getClassLoader().getResourceAsStream("db.properties");            Properties prop = new Properties();            prop.load(in);            driver = prop.getProperty("driver");            url = prop.getProperty("url");            username = prop.getProperty("username");            password = prop.getProperty("password");        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    /**     * 获取连接方法     * @return     */    public static Connection getConnection(){        Connection conn = null;        try {            Class.forName(driver);            String url = "jdbc:mysql://localhost:3306/web08";            conn = DriverManager.getConnection(url,username , password);        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return conn;    }    public static void release(Connection conn,PreparedStatement pstmt,ResultSet rs){        if(rs!=null)            try {                rs.close();            } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        if(pstmt!=null)            try {                pstmt.close();            } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        if(conn!=null)            try {                conn.close();            } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }    }}

3：使用装饰者模式重写获取连接的方法和关闭连接的close()方法

package cn.itheima.jdbc.dataSource;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.NClob;import java.sql.PreparedStatement;import java.sql.SQLClientInfoException;import java.sql.SQLException;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;//1.实现同一个接口Connectionpublic class MyConnection implements Connection{    //3.定义一个变量    private Connection conn;    private LinkedList<Connection> pool;    //2.编写一个构造方法(参数使用了面向对象的多态)    public MyConnection(Connection conn,LinkedList<Connection> pool) {        this.conn = conn;        this.pool = pool;    }    //4.书写需要增强的方法    @Override    public void close() throws SQLException {        pool.add(conn);    }    //5.！！！此方法必须覆盖，否则会出现空指针异常    @Override    public PreparedStatement prepareStatement(String sql) throws SQLException {        return conn.prepareStatement(sql);    }    ...其他实现类}

4：创建连接池并获取连接

package cn.itheima.jdbc.dataSource;import java.io.PrintWriter;import java.sql.Connection;import java.sql.SQLException;import java.sql.SQLFeatureNotSupportedException;import java.util.LinkedList;import java.util.logging.Logger;import javax.sql.DataSource;import cn.itheima.jdbc.utils.JDBCUtils_V3;public class MyDataSource2 implements DataSource {    //1.创建一个容器用于存储Connection对象    private static LinkedList<Connection> pool = new LinkedList<Connection>();    //2.创建5个连接放到容器中去    static{        for (int i = 0; i < 5; i++) {            Connection conn = JDBCUtils_V3.getConnection();            //放入池子中的Connection对象已经经过改造            **MyConnection myconn = new MyConnection(conn, pool);**            pool.add(myconn);        }    }    /**     * 重写获取连接的方法     */    @Override    public Connection getConnection() throws SQLException {        Connection conn = null;        //3.使用前先判断        if(pool.size()==0){            //4.再创建5个连接            for (int i = 0; i < 5; i++) {                conn = JDBCUtils_V3.getConnection();                **MyConnection myconn = new MyConnection(conn, pool);**                pool.add(myconn);            }        }        //5.从池子里获取连接对象Connection        conn = pool.remove(0);        return conn;    }    /**     * 归还连接对象到连接池     */    public void backConnection(Connection conn){        pool.add(conn);    }}}

5：编写测试类

package cn.itheima.jdbc.test;import java.sql.Connection;import java.sql.PreparedStatement;import org.junit.Test;import cn.itheima.jdbc.dataSource.MyDataSource;import cn.itheima.jdbc.dataSource.MyDataSource2;import cn.itheima.jdbc.utils.JDBCUtils_V3;public class TestMyDataSource2 {    /**     * 添加用户，使用改造的Connection方法     */    @Test    public void addUser(){        Connection conn = null;        PreparedStatement pstmt = null;        //1.创建自定义连接池        MyDataSource2 dataSource = new MyDataSource2();        try {            //2.从池子中获取连接            conn = dataSource.getConnection();            String sql = "insert into tbl_user values(null,?,?)";            //必须在自定义的Connection类中重写prepareStatement(sql)方法            pstmt = conn.prepareStatement(sql);            pstmt.setString(1, "吕布1");            pstmt.setString(2, "貂蝉1");            int rows = pstmt.executeUpdate();            if(rows>0){                System.out.println("添加成功");            }else {                System.out.println("添加失败");            }        } catch (Exception e) {            throw new RuntimeException(e);        } finally {            JDBCUtils_V3.release(conn, pstmt, null);        }    }}

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