package top.qaqaq.P23.statement.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.Scanner;

import org.junit.Test;

import top.qaqaq.P12.statement.crud.User;
import top.qaqaq.P14.util.JDBCUtils;

/**
 * 
 * @Description 演示使用PreparedStatement替换Statement，解决SQL注入问题
 * @author RichieZhang Email:18358892@qq.com
 * @version
 * @date 2022年11月26日下午9:29:01
 *
 */
public class PreparedStatementTest {

	@Test
	public void testLogin() {
		Scanner scanner = new Scanner(System.in);
		
		System.out.print("请输入用户名：");
		String user = scanner.nextLine();
		System.out.print("请输入密码：");
		String password = scanner.next();
		//SELECT user,password FROM user_table WHERE user = '1' or ' AND password = '=1 or '1' = '1'
		String sql = "SELECT user,password FROM user_table WHERE user = ? AND password = ?";
		User returnUser = getInstance(User.class, sql, user, password);
		if(returnUser != null) {
			System.out.println("登陆成功");
		}else {
			System.out.println("用户名不存在或密码错误");
		}
		
	}
	
	/**
	 * 
	 * @Description
	 * @author RichieZhang 针对于不同的表的通用的查询操作，返回表中的一条记录
	 * @date 2022年11月26日下午9:04:58
	 * @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.getConnection();

			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
			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 columnvalue = rs.getObject(i + 1);

					// 获取每个列的列名
//					String columnName = rsmd.getColumnName(i + 1);
					String columnLabel = rsmd.getColumnLabel(i + 1);

					// 给t对象指定的columnName属性，赋值为columnvalue；通过反射
					Field field = clazz.getDeclaredField(columnLabel);
					field.setAccessible(true);
					field.set(t, columnvalue);

				}
				return t;
			}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			JDBCUtils.closeResource(conn, ps, rs);
		}

		return null;
	}

}