userdao.java

JSPHelloWorld小程序 我自己做的 可能跟书上有所不同把

/**
 * 
 */
package user.dao;

import java.sql.*;

import user.entity.User;

/**
 * 用户数据访问层.
 * @author BeanSoft
 *
 */
public class UserDAO {
	/**
	 * 根据用户名和密码查找用户, 找到了返回 user 对象. 否则返回 null.
	 * @param user 携带用户名和密码的用户对象
	 * @return 查找结果
	 */
	public User findUserByUsernamePassword(User user) {
		// 1. 注册驱动
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}// Mysql 的驱动
		
		java.sql.Connection conn = null;
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		
		try {
			// 2. 获取数据库的连接
			conn = java.sql.DriverManager.getConnection(
					"jdbc:mysql://localhost/test?useUnicode=true&characterEncoding=GBK", "root", null);
			
			pstmt = conn.prepareStatement("select * from myuser where username = ? and password = ?");
			
			pstmt.setString(1, user.getUsername());
			pstmt.setString(2, user.getPassword());
			
			rs = pstmt.executeQuery();
			
			if(rs != null && rs.next()) {
				user.setId(rs.getInt("id"));
				return user;
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			try {
				rs.close();
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
			try {
				pstmt.close();
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
			try {
				conn.close();
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		return null;

	}
}