JDBC PreparedStatement针对不同表的通用查询操作

PreparedStatement针对不同表的通用查询操作：

package com.atguigu3.preparedstatement.crud;


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

import org.junit.Test;

import com.atguigu3.bean.Customer;
import com.atguigu3.bean.Order;
import com.atguigu3.util.JDBCUtils;

/*
 * 使用preparedStatement实现针对于不同表的通用的查询操作
 */
public class PreparedStatementQueryTest {
	@Test
	public void testGetForList() {
		String sql="select id,name,email from customers where id<?";
		List<Customer> list = getForList(Customer.class, sql, 12);
		list.forEach(System.out::println);
		
		String sql1="select order_id orderId,order_name orderName from `order` ";
		List<Order> orderList = getForList(Order.class, sql1);
		orderList.forEach(System.out::println);
	}
	
	
	public <T> List<T> getForList(Class<T> clazz, String sql,Object...args){
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		try {
			conn = JDBCUtils.getConnectio();
			
			ps = conn.prepareStatement(sql);
			for (int i = 0; i < args.length; i++) {
				ps.setObject(i+1,args[i]);
			}
			
			rs = ps.executeQuery();
			//获取结果集的元数据 
			ResultSetMetaData rsmd = rs.getMetaData();
			//通过ResultSetMetaData获取结果集中的列数
			int columnCount = rsmd.getColumnCount();
			//创建集合对象
			ArrayList<T> list = new ArrayList<T>();
			while(rs.next()) {
				T t=clazz.newInstance();
				//处理结果集一行数据中的每一个列:给T对象指定的属性赋值
				for (int i = 0; i < columnCount; i++) {
					//获取列值
					Object columValue = rs.getObject(i+1);
					
					//获取每个列的列名
					String columnLable = rsmd.getColumnLabel(i+1);
					
					//给t对象指定的columnName属性，赋值为columValue,通过反射
					Field field=clazz.getDeclaredField(columnLable);
					field.setAccessible(true);
					field.set(t, columValue);
				}
				list.add(t);
			}
			return list;
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			JDBCUtils.closeResource(conn, ps,rs);

		}
		return null;
	}
	
	
	
	
	//------------------------------------------------------------------------
	@Test
	public void testGetInstance() {
		String sql="select id,name,email from customers where id=?";
		Customer customer = getInstance(Customer.class, sql, 12);
		System.out.println(customer);
		
		String sql1="select order_id orderId,order_name orderName from `order` where order_id=?";
		Order order = getInstance(Order.class, sql1, 1);
		System.out.println(order);
	}
	
	/**
	 * 针对不同表的通用查询操作，返回表中的一条记录  
	 * @param <T>
	 * @param clazz
	 * @param sql
	 * @param args
	 * @return
	 */
	public <T> T getInstance(Class<T> clazz, String sql,Object...args) {
		Connection conn=null;
		PreparedStatement ps=null;
		ResultSet rs=null;
		try {
			conn = JDBCUtils.getConnectio();
			
			ps = conn.prepareStatement(sql);
			for (int i = 0; i < args.length; i++) {
				ps.setObject(i+1,args[i]);
			}
			
			rs = ps.executeQuery();
			//获取结果集的元数据 
			ResultSetMetaData rsmd = rs.getMetaData();
			//通过ResultSetMetaData获取结果集中的列数
			int columnCount = rsmd.getColumnCount();
			
			if(rs.next()) {
				T t=clazz.newInstance();
				//处理结果集一行数据中的每一个列
				for (int i = 0; i < columnCount; i++) {
					//获取列值
					Object columValue = rs.getObject(i+1);
					
					//获取每个列的列名
					String columnLable = rsmd.getColumnLabel(i+1);
					
					//给t对象指定的columnName属性，赋值为columValue,通过反射
					Field field=clazz.getDeclaredField(columnLable);
					field.setAccessible(true);
					field.set(t, columValue);
				}
				return t;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			JDBCUtils.closeResource(conn, ps,rs);

		}
		return null;
	}
		
		
		
	}