DBUtils的封装

package com.zuxia.util;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class DBUtil {
	//定义私有的静态的常量字符串
	private static final String USERNAME="root";
	private static final String PASSWORD="123456";
	private static final String URL="jdbc:mysql://localhost:3306/userdb?characterEncoding=utf8";
	private static final String DRIVER_URL="com.mysql.jdbc.Driver";
	
	//静态语句块(优先执行且只执行1次)————加载驱动
	static{
		try {
			Class.forName(DRIVER_URL);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	
	//公开的静态的方法————获取连接对象
	public static Connection getConn(){
		try {
			return DriverManager.getConnection(URL, USERNAME, PASSWORD);
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return null;
	}
	
	public static void getClose(Connection conn,PreparedStatement ps,ResultSet rs){
		try {
			if(rs!=null) rs.close();
			if(ps!=null) ps.close();
			if(conn!=null) conn.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	//通用的增删改方法
	public static int commonsZSG(String sql,Object... params){
		Connection conn=DBUtil.getConn();
		PreparedStatement ps=null;
		ResultSet rs=null;
		try {
			ps=conn.prepareStatement(sql);
			
			//如果有参数时，再进行遍历赋值
			if(params!=null && params.length>0){
				//可变参数：实质是一个数组
				for(int i=0;i<params.length;i++){
					ps.setObject(i+1, params[i]);
				}
			}
			
			return ps.executeUpdate();
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			DBUtil.getClose(conn, ps, rs);
		}
		return 0;
	}
	//通用的查询方法
	public static List commonsQuery(String sql,Class cla,Object... params){
		Connection conn=DBUtil.getConn();
		PreparedStatement ps=null;
		ResultSet rs=null;
		List list=new ArrayList();
		try {
			ps=conn.prepareStatement(sql);
			//如果有参数时，再进行遍历赋值
			if(params!=null && params.length>0){
				//可变参数：实质是一个数组
				for(int i=0;i<params.length;i++){
					ps.setObject(i+1, params[i]);
				}
			}
			rs=ps.executeQuery();
			while(rs.next()){
				Object obj = reflect(cla, rs);
				//加入集合
				list.add(obj);
			}
		} catch (SQLException e) {
			e.printStackTrace();
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}finally{
			DBUtil.getClose(conn, ps, rs);
		}
		return list;
	}
	//递归
	private static Object reflect(Class cla,ResultSet rs) throws InstantiationException, IllegalAccessException, IllegalArgumentException, SQLException, ClassNotFoundException{
		Object obj = cla.newInstance();
		Field[] fl = cla.getDeclaredFields();
		for(Field f : fl){
			f.setAccessible(true);
			if(f.getType().getName().contains("zuxia")){//对象
				Object refObj = reflect(Class.forName(f.getType().getName()),rs);
				f.set(obj, refObj);
			}else{//普通字段
				f.set(obj, rs.getObject(f.getName()));
			}
		}
		return obj;
	}
	
}