studentdao.java

MyEclipse6Java中文教程的代码

package dao;
import java.sql.SQLException;
import entity.Student;
/**
 * 学生数据访问类
 * @author [e-mail]
 * @version 0.1 2007-12-21
 */
public class StudentDAO {
	/**
	 * 根据用户名和密码找到用户对象。
	 * @param username 用户名
	 * @param password 密码
	 * @return 找到的用户对象，找不到返回null
	 */
	public Student findStudent(String username, String password) {
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}

		java.sql.Connection conn = null;//数据库连接
		java.sql.PreparedStatement pstmt = null;//数据库表达式
		java.sql.ResultSet rs = null;//结果集
		String sql = "select * from Student where username = ? and password = ?";//SQL
		
		try {
			conn = java.sql.DriverManager.getConnection(
					"jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=GBK", "root", null);

			pstmt = conn.prepareStatement(sql);
			
			pstmt.setString(1, username);
			pstmt.setString(2, password);

			rs = pstmt.executeQuery();
			
			if(rs !=null && rs.next()) {
				// 读到数据，生成实体类
				Student student = new Student();
				
				student.setId(rs.getInt(1));
				student.setUsername(rs.getString("username"));
				student.setPassword(rs.getString("password"));
				student.setAge(rs.getInt("age"));
				
				return student;
			}
		} catch (SQLException e) {
			e.printStackTrace();
		} finally {
			// 6. 释放资源，建议放在finally语句中确保都被关闭掉了
			try {
				rs.close();
			} catch (SQLException e) {}
			try {
				pstmt.close();
			} catch (SQLException e) {}
			try {
				conn.close();
			} catch (SQLException e) {}
		}
		
		return null;
	}
	
	public static void main(String[] args) {
		Student student = new StudentDAO().findStudent("张三","1234");
		System.out.println(student.getUsername());
	}
}