java_web学习第十一天(jdbc数据库驱动------数据库连接池)

数据库连接池：就是将链接数据库的链接保存到一个池子中，用的时候从池子中获取数据库连接，不用的时候将其放到池子中国，。连接池就是用来存放数据库的链接。传统方式：要连接数据库的时候，获取数据库，然后执行操作，用完之后，关闭数据库连接。连接池方式：在启动数据库驱动的时候，就在连接池中存放几条数据库的链接，应用程序要操作数据库的时候，只要去池子中获取连接，执行操作，之后将链接放在池子中，就可以了。原因：用户每次请求都需要向数据库获得连接，而数据库创建连接通常需要消耗相对较大的资源，创建时间也较长。自己自定义数据库连接池：

dataSource.properties配置文件：

jdbcUrl:jdbc:mysql://localhost:3306/jdbcuser:rootpassword:rootdriverName:com.mysql.jdbc.DriverpoolSize:5

自定义数据库连接池：

package com.enterise.always.servlet;import java.io.IOException;import java.io.InputStream;import java.io.PrintWriter;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.util.LinkedList;import java.util.Properties;import javax.sql.DataSource;/** * 数据库连接池 *  * @author Always *  */public class MyDataSource implements DataSource {// 鏈錶連接池private static LinkedList<Connection> connPool = new LinkedList<Connection>();private static LinkedList<Connection> prePool = new LinkedList<Connection>();private static int poolSize = 5;private static Properties properties = new Properties();static {// 1.获取配置信息InputStream inStream = MyDataSource.class.getClassLoader().getResourceAsStream("/dataSource.properties");// 2.加载配置信息资源try {properties.load(inStream);inStream.close();// 3.注册驱动器Class.forName(properties.getProperty("driverName"));// 4获取数据库连接数poolSize = Integer.parseInt(properties.getProperty("poolSize"));// 5.批量添加数据库链接addConnNum();} catch (IOException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();} catch (SQLException e) {e.printStackTrace();}}/** * 添加数据库链接 *  * @throws SQLException */public static void addConnNum() throws SQLException {for (int i = 0; i < poolSize; i++) {Connection connection = DriverManager.getConnection(properties.getProperty("jdbcUrl"), properties.getProperty("user"),properties.getProperty("password"));connPool.add(connection);}}public Connection getConnection() throws SQLException {Connection conn = null;if (connPool.size() > 0) {conn = connPool.getFirst();prePool.add(conn);connPool.removeFirst();} else {// 再添加链接数addConnNum();// 再次链接getConnection();}return conn;}/** * 关闭链接 *  * @param conn */public void closeConn(Connection conn) {connPool.add(conn);prePool.remove(conn);}public Connection getConnection(String username, String password)throws SQLException {return null;}public PrintWriter getLogWriter() throws SQLException {return null;}public int getLoginTimeout() throws SQLException {return 0;}public void setLogWriter(PrintWriter out) throws SQLException {}public void setLoginTimeout(int seconds) throws SQLException {}public boolean isWrapperFor(Class arg0) throws SQLException {return false;}public Object unwrap(Class arg0) throws SQLException {return null;}}
开源的数据库连接池：DBCP 数据库连接池C3P0 数据库连接池DBCP:DBCP 是 Apache 软件基金组织下的开源连接池实现.jar包：Commons-dbcp.jar,Commons-pool.jarprivate static BasicDataSource dataSource = new BasicDataSource();//设置数据源的参数。dataSource.setUrl("jdbc:mysql://localhost:3306/jdbc");dataSource.setUsername("root");dataSource.setPassword("root");dataSource.setInitialSize(10);或者：InputStream inStream = DBCPDataSource.class.getClassLoader().getResourceAsStream("/dataSource.properties");Properties properties = new Properties();try {properties.load(inStream);inStream.close();DataSource ds = BasicDataSourceFactory.createDataSource(properties);} catch (IOException e) {e.printStackTrace();} catch (Exception e) {e.printStackTrace();}C3P0：private static ComboPooledDataSource dataSource = new ComboPooledDataSource();static {try {dataSource.setDriverClass("com.mysql.jdbc.Driver");} catch (PropertyVetoException e) {e.printStackTrace();}dataSource.setJdbcUrl("jdbc:mysql://localhost:3306/jdbc");dataSource.setPassword("root");dataSource.setUser("root");}或者：private static ComboPooledDataSource dataSource = new ComboPooledDataSource("/dataSource.properties");