JDBC优化之路-3（使用C3P0连接池）

3.在2的基础上修改DBUtil.java,新建DBDataSource.java和db.properties属性文件

项目结构：

修改后的DBUtil.java

package com.hpe.util;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class DBUtil {
	/*
	 * 获取数据库连接
	 */
//	public static Connection getConn() throws ClassNotFoundException, SQLException{
//		Class.forName("com.mysql.jdbc.Driver");
//		
//		String url = "jdbc:mysql://localhost:3306/work?useUnicode=true&characterEncoding=utf-8";
//		String username="root";
//		String password="root";
//	    Connection conn=DriverManager.getConnection(url, username, password);
//	    return conn;
//	}
	/*
	 * 关闭数据库资源
	 */
	public static void close(ResultSet rs,PreparedStatement ps,Connection conn){
		try {
			if(rs!=null){
				rs.close();
			}		
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			if(ps!=null){
				ps.close();
			}		
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			if(conn!=null){
				conn.close();
			}		
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	/*
	 * Class<T> type创建什么类型的对象
	 * T用来保存一个参数类型
	 */
	public static <T> List<T> select(String sql,Object[] params,Class<T> type){
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		List<T>list =new ArrayList<>();
		try {
			conn=DBDataSource.getConn();		
			ps=conn.prepareStatement(sql);
			if(params != null){
				for(int i=0;i<params.length;i++){
					ps.setObject(i+1, params[i]);
				}
			}	
			rs  = ps.executeQuery();
			ResultSetMetaData metaData = rs.getMetaData();//
			int colCount = metaData.getColumnCount();//获取列的数量
			while(rs.next()){			
				/*
				 * 把数据库查询出来的通过内省丢给Object
				 */
				T obj = type.newInstance();
				BeanInfo beanInfo = Introspector.getBeanInfo(type);//obj的属性
				PropertyDescriptor[] properties = beanInfo.getPropertyDescriptors();//属性信息的数组
				
				for (int i = 0; i < colCount; i++) {
					String cloName = metaData.getColumnName(i+1);	//获取到列名	
					Object value = rs.getObject(i+1);//列的值
					
					/*
					 * 遍历properties数组，找到一个名字和cloName一样的属性
					 */
					for(int j=0;j<properties.length;j++){
						PropertyDescriptor property = properties[j];
						String propertyName = property.getName();//属性名字
						Method method = property.getWriteMethod();//写方法
						
						if(propertyName.equals(cloName)){
							//属性名与数据表的列名一样，将值传给obj
							method.invoke(obj, value);
						}
					}
				
				}
				list.add(obj);
			}		
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IntrospectionException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InvocationTargetException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {
			close(rs, ps, conn);
		}
		return list;
	}
	public static <T> T  selectObject(String sql,Object[] params,Class<T> type){
		List<T> list = select(sql, params,type);
		T resObj = null;
		if(list.size()>0){
			resObj=list.get(0);
		} 
		return resObj;
	}
	
	/*
	 * UPdate方法, 支持增,删,改
	 */
	public static int update(String sql, Object[] params){
		
		Connection conn = null;
		PreparedStatement ps = null;		
		int res = 0;
		
		try {
			conn = DBDataSource.getConn();		
			ps = conn.prepareStatement(sql);	
			
			if (params != null){
				for (int i=0; i<params.length; i++){
					ps.setObject(i+1, params[i]);
				}
			}			
			res = ps.executeUpdate();			
		} catch (SQLException e) {
			e.printStackTrace();
		}finally {
			close(null, ps, conn);
		}	
		return res;
	}
}

数据源DBDataSource.java

package com.hpe.util;

import java.beans.PropertyVetoException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

import com.mchange.v2.c3p0.ComboPooledDataSource;

/*
 * 提供数据库连接对象，使用C3P0
 */
public class DBDataSource {
	public static String driver;//驱动
	public static String url;//数据库地址
	public static String username;//数据库帐号
	public static String password;//数据库密码
	public static int maxPoolSize;//最大连接池数
	public static int minPoolSize;//最小连接池数
	public static int initialPoolSize;//初始化连接池数
	public static int checkoutTimeout;//超时
	
	private static ComboPooledDataSource dataSource =null;//数据源
	
	static{
		try{
			Properties properties = new Properties();//加载后缀是properties的属性文件
			InputStream inputStream = DBDataSource.class.getClassLoader().getResourceAsStream("db.properties");
			properties.load(inputStream);
			driver = properties.getProperty("drivername");
		        url = properties.getProperty("url");
			username = properties.getProperty("username");
			password = properties.getProperty("password");
			
			maxPoolSize =Integer.parseInt(properties.getProperty("maxPoolSize"));
			minPoolSize =Integer.parseInt(properties.getProperty("minPoolSize"));
			initialPoolSize =Integer.parseInt(properties.getProperty("initialPoolSize"));
			checkoutTimeout =Integer.parseInt(properties.getProperty("checkoutTimeout"));
		}	catch (Exception e) {
		// TODO Auto-generated catch block
		e.printStackTrace();
	}
	}
	
	/**************** c3p0 数据库连接池 启动方法******************/
	private static void initDataSource() {
		dataSource = new ComboPooledDataSource();
		try {		
			dataSource.setDriverClass(driver);
			dataSource.setJdbcUrl(url);
			dataSource.setUser(username);
			dataSource.setPassword(password);
			dataSource.setMaxPoolSize(maxPoolSize);
			dataSource.setMinPoolSize(minPoolSize);
			dataSource.setInitialPoolSize(initialPoolSize);
			dataSource.setCheckoutTimeout(checkoutTimeout);
		} catch (PropertyVetoException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} 
	}	
	/**
	 * c3p0数据库连接入
	 * @return
	 * @throws Exception
	 */
	public static Connection getConn() throws SQLException{
		if(dataSource == null){
			initDataSource();
		}
		Connection conn = dataSource.getConnection();
		return conn;
	}
}

db.properties属性文件

############
drivername=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/work?useUnicode=true&characterEncoding=utf-8
username=root
password=root
##########//c3p0	
maxPoolSize=200
minPoolSize=5
initialPoolSize=10
checkoutTimeout=300000