DBUtil.java JDBCUtil.java(又分为使用C3P0和不使用C3P0两种)的对比

今天我和认真的学习了传智播客的连接池的知识，学完之后，和以前使用的DBUtil混了，决定把他们一起罗列一下，供我以后查看。
首先，贴一下比较基础的DBUtil.java的代码，这是还没学连接池以前，所使用的比较基础的东西

package com.hpe.util;

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

public class DBUtil {
	//1.定义链接数据库的属性
	private static String driver="com.mysql.jdbc.Driver";
	private static String url="jdbc:mysql://localhost:3306/personlife?useUnicode=true&characterEncoding=UTF-8&useSSL=true";
	private static String username="root";
	private static String password="123456";
	static{//静态代码块，只在类第一次被调用时加载
		try {
			Class.forName(driver);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	//2.获取数据库的链接
	public static Connection getConn(){
		Connection conn=null;
		//加载驱动
		try {
			
			//.获取数据库链接
			 conn=DriverManager.getConnection(url, username, password);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return conn;
		
	}
	//关闭资源
	//1.关闭结果集
	public static void closeRs(ResultSet rs){
		//避免空指针
		if(rs!=null){
			try {
				rs.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
	}
	//1.关闭预编译语句
		public static void closePs(PreparedStatement ps){
			//避免空指针
			if(ps!=null){
				try {
					ps.close();
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			
		}
		//1.关闭链接
		public static void closeConn(Connection conn){
			//避免空指针
			if(conn!=null){
				try {
					conn.close();
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			
		}
}

学完连接池之后，转去使用JDBCUtil.java。其中，原始的不使用C3P0的代码是这样。另外还需要配置文件jdbc.properties
driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost/bank
name=root
password=root

package com.itheima.uitl;

import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCUtil {
	
	static String driverClass = null;
	static String url = null;
	static String name = null;
	static String password= null;
	
	static{
		try {
			//1. 创建一个属性配置对象
			Properties properties = new Properties();
			InputStream is = new FileInputStream("jdbc.properties");
			
			//使用类加载器，去读取src底下的资源文件。 后面在servlet
//			InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
			//导入输入流。
			properties.load(is);
			
			//读取属性
			driverClass = properties.getProperty("driverClass");
			url = properties.getProperty("url");
			name = properties.getProperty("name");
			password = properties.getProperty("password");
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 获取连接对象
	 * @return
	 */
	public static Connection getConn(){
		Connection conn = null;
		try {
			Class.forName(driverClass);
			//静态代码块 ---> 类加载了，就执行。 java.sql.DriverManager.registerDriver(new Driver());
			//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
			//DriverManager.getConnection("jdbc:mysql://localhost/test?user=monty&password=greatsqldb");
			//2. 建立连接 参数一： 协议 + 访问的数据库 ， 参数二： 用户名 ， 参数三： 密码。
			conn = DriverManager.getConnection(url, name, password);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return conn;
	}
	
	/**
	 * 释放资源
	 * @param conn
	 * @param st
	 * @param rs
	 */
	public static void release(Connection conn , Statement st , ResultSet rs){
		closeRs(rs);
		closeSt(st);
		closeConn(conn);
	}
	public static void release(Connection conn , Statement st){
		closeSt(st);
		closeConn(conn);
	}

	
	private static void closeRs(ResultSet rs){
		try {
			if(rs != null){
				rs.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			rs = null;
		}
	}
	
	private static void closeSt(Statement st){
		try {
			if(st != null){
				st.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			st = null;
		}
	}
	
	private static void closeConn(Connection conn){
		try {
			if(conn != null){
				conn.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			conn = null;
		}
	}
}

而使用了C3P0的JDBCUtil则相对简单一些，不过也需要配置文件c3p0-config.xml，其实也可以使用后缀为.properties的文件，但是xml比较常用

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>

	<!-- default-config 默认的配置，  -->
  <default-config>
    <property name="driverClass">com.mysql.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://localhost/bank</property>
    <property name="user">root</property>
    <property name="password">root</property>
    
    
    <property name="initialPoolSize">10</property>
    <property name="maxIdleTime">30</property>
    <property name="maxPoolSize">100</property>
    <property name="minPoolSize">10</property>
    <property name="maxStatements">200</property>
  </default-config>
  
   <!-- This app is massive! -->
  <named-config name="oracle"> 
    <property name="acquireIncrement">50</property>
    <property name="initialPoolSize">100</property>
    <property name="minPoolSize">50</property>
    <property name="maxPoolSize">1000</property>

    <!-- intergalactoApp adopts a different approach to configuring statement caching -->
    <property name="maxStatements">0</property> 
    <property name="maxStatementsPerConnection">5</property>

    <!-- he's important, but there's only one of him -->
    <user-overrides user="master-of-the-universe"> 
      <property name="acquireIncrement">1</property>
      <property name="initialPoolSize">1</property>
      <property name="minPoolSize">1</property>
      <property name="maxPoolSize">5</property>
      <property name="maxStatementsPerConnection">50</property>
    </user-overrides>
  </named-config>

 
</c3p0-config>
	

package com.itheima.uitl;

import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JDBCUtil02 {
	
	static ComboPooledDataSource dataSource = null;
	static{
		dataSource = new ComboPooledDataSource();
	}
	
	/**
	 * 获取连接对象
	 * @return
	 * @throws SQLException 
	 */
	public static Connection getConn() throws SQLException{
		return dataSource.getConnection();
	}
	
	/**
	 * 释放资源
	 * @param conn
	 * @param st
	 * @param rs
	 */
	public static void release(Connection conn , Statement st , ResultSet rs){
		closeRs(rs);
		closeSt(st);
		closeConn(conn);
	}
	public static void release(Connection conn , Statement st){
		closeSt(st);
		closeConn(conn);
	}

	
	private static void closeRs(ResultSet rs){
		try {
			if(rs != null){
				rs.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			rs = null;
		}
	}
	
	private static void closeSt(Statement st){
		try {
			if(st != null){
				st.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			st = null;
		}
	}
	
	private static void closeConn(Connection conn){
		try {
			if(conn != null){
				conn.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			conn = null;
		}
	}
}