userdao.java

只做是单选题！数据库表有三张：EUser,EItem,Score

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package com.exam.model;

/**
 *
 * @author fyadmin
 */
import java.sql.*;
import javax.sql.DataSource;

import javax.naming.Context;
import javax.naming.InitialContext;

import javax.naming.NamingException;

public class UserDAO {

    private static final String GET_EUSER = "SELECT *  FROM EUSER where username=? and password=?";

    public UserDAO() {
    }

    public User retrieve(String username, String password) throws SQLException {

        DataSource ds = null;

        Connection con = null;
        PreparedStatement ps = null;//语句
        ResultSet rs = null;//结果
        User users = null;

        try {
            Context ctx = new InitialContext();//得到JNDI
            if (ctx == null) {
                throw new RuntimeException("JNDI Context could not be found.");
            }
            ds = (DataSource) ctx.lookup("jdbc/examDB");
            if (ds == null) {
                throw new RuntimeException("DataSource could not be found.");

            }
            con = ds.getConnection();//得到连接通道
            ps = con.prepareStatement(GET_EUSER);
            ps.setString(1, username);
            ps.setString(2, password);
            rs = ps.executeQuery();//结果通道

            while (rs.next()) {
                int objectID = rs.getInt("UID");
                users = new User(objectID,
                        rs.getString("username"),
                        rs.getString("password"));
            }

        } catch (NamingException ne) {
            throw new RuntimeException("A JNDI error occured." + ne.getMessage());
        } finally {
            if (rs != null) {
                try {
                    rs.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }

            }
            if (ps != null) {
                try {
                    ps.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            if (con != null) {
                try {
                    con.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            return users;
        }
    }
}