连接数据库 JDBC、DBCP、JNDI

一、JDBC

package com.direct.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class JDBCutil {
	/*
	 * 目前使用的JDBC连接数据库，存在问题：
	 * 每次连接和释放需要比较多的资源
	 * 资源浪费比较严重，系统的性能下滑
	 *
	 * 连接池的原理：
	 * 提前设定好，数据库的连接对象，当用户连接数据库时，直接从
	 * “池子”中取出一个连接即可。
	 * 当用户使用完毕后，“关闭连接”不是物理关闭，而是把连接放回连接池中
	 */

	private static final String DRIVER="com.mysql.jdbc.Driver";
	private static final String URL="jdbc:mysql://localhost:3306/countryside_buy?userUnicode=true&characterEncoding=utf-8";
	private static final String USER="root";
	private static final String PWD="123456";
	static{
		try {
			Class.forName(DRIVER);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	//获得链接
	public Connection createConn(){
		Connection conn = null;
		try {
			conn = DriverManager.getConnection(URL, USER, PWD);
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return conn;
	}

	//关闭连接
	public void closeJ(Connection conn,PreparedStatement ps,ResultSet rs) throws SQLException{
		if(rs!=null)  rs.close();
		if(ps!=null)  ps.close();
		if(conn!=null)  conn.close();
	}
}

　　

二，DBCP

2.1 dbcp.properties

username=root
password=123456
driverClassName=com.mysql.jdbc.Driver
maxActive=2000
maxIdle=520
maxWait=5000
url=jdbc\:mysql\://localhost\:3306/countryside_buy

2.2 DBCPutil

package com.direct.util;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.ResourceBundle;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSource;
/*
 * DBCP使用步骤：
 * 1，下载需要的jar包，放入web项目的lib下面
 * 2，在src下面建立配置文件   .properties
 * 3,   建立连接数据库工具，获取配置信息，
 * 4，commons-dbcp.jar
 *        commons-pool-1.5.3.jar
 *        musql-connector-java-5.1.7.jar
 */

public class DBCPutil {
	//数据源
	private static DataSource  ds= null;
	//基本数据源
	static BasicDataSource bds =  new BasicDataSource();
	public static Connection getconn() throws SQLException{
		if (ds==null) {
			ResourceBundle rs = ResourceBundle.getBundle("dbcp");
			String username = rs.getString("username");
			String password = rs.getString("password");
			String driverClassName = rs.getString("driverClassName");
			String maxActive = rs.getString("maxActive");
			String maxIdle = rs.getString("maxIdle");
			String maxWait = rs.getString("maxWait");
			String url = rs.getString("url");

			bds.setMaxActive(Integer.parseInt(maxActive));
			bds.setMaxIdle(Integer.parseInt(maxIdle));
			bds.setMaxWait(Integer.parseInt(maxWait));
			bds.setUrl(url);
			bds.setUsername(username);
			bds.setPassword(password);
			bds.setDriverClassName(driverClassName);

			ds = bds;
				return ds.getConnection();

		}
		return ds.getConnection();
	}
	//测试
	public static void main(String[] args) {
		try {
			System.out.println(getconn());
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}

}

三，JNDI

1，所需放在tomcat安装路径的lib目录下  commons.pool-1.5.3.jar  和  mysql-connector-java-5.1.7-bin.jar

2，tomcat中找到config文件夹下的context.xml

在标签<Context>中添加

	<Resource
	  name="jndiDemo"
	  auth="Container"
	  type="javax.sql.DataSource"
      driverClassName="com.mysql.jdbc.Driver"
      url="jdbc:mysql://localhost:3306/countryside_buy"
	  username="root"
	  password="123456"
	  maxActive="100"
	  maxIdle="30"
	  maxWait="3000"
   />

3，项目的web.xml中添加映射

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
	xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

	<!-- 配置JNDI -->
	<resource-ref>
		<res-ref-name>jndiDemo</res-ref-name>
		<res-type>javax.sql.DataSource</res-type>
		<res-auth>Container</res-auth>
	</resource-ref>

<servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>JndiServlet</servlet-name>
    <servlet-class>com.direct.servlet.JndiServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>JndiServlet</servlet-name>
    <url-pattern>/JndiServlet</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
    <welcome-file>register.jsp</welcome-file>
  </welcome-file-list>
</web-app>

4，jndi类

package com.direct.util;

import java.sql.Connection;
import java.sql.SQLException;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;

public class JNDIutil {
	/*
	 * JNDI是tomcat提供的一种标准的连接池
	 * 1，将驱动放入项目中tomcat的lib目录下
	 * 2，修改配置文件（tomcat中找到config文件夹下的context.xml）
	 * 3，在web.xml下配置
	 */
	public static Connection conn(){
		Connection connection = null;
		try {
			//获得对数据源的引用
			Context context = new InitialContext();
			DataSource ds = (DataSource)context.lookup("java:comp/env/jndiDemo");
			//获得数据库连接对象
			connection = ds.getConnection();
		} catch (NamingException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return connection;

	}
}

　5，servlet 测试jndi

package com.direct.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.direct.util.JNDIutil;

public class JndiServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doPost(request, response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html");
		System.out.println(new JNDIutil().conn());
		//jdbc:mysql://localhost:3306/countryside_buy, UserName=root@localhost, MySQL-AB JDBC Driver

	}

}

　　最后开启服务器，访问 jndiServlet 后台即可得到连接，并输出连接地址