JavaWeb课程复习资料（六）——DAO与DAOImpl层封装

package com.item.dao;
import com.item.pojo.UserInfo;
import java.util.List;
public interface UserInfoDAO {
    /**
     * 查询所有用户信息
     * @return
     */
    public List<UserInfo> GetAll();
    /**
     * 添加用户
     * @param info
     * @return
     */
    public boolean InsertUserInfo(UserInfo info);
    /**
     * 单个ID查询
     * @param id
     * @return
     */
    public UserInfo SelectById(int id);
    /**
     * 修改用户信息
     * @param info
     * @return
     */
    public boolean UpdateById(UserInfo info);
    /**
     * 根据id删除用户
     * @param id
     * @return
     */
    public boolean DeleteById(int id);
}

package com.item.daoimpl;
import com.item.dao.UserInfoDAO;
import com.item.jdbc.FactoryDB;
import com.item.pojo.UserInfo;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.LinkedList;
import java.util.List;
public class UserInfoDAOImpl implements UserInfoDAO {
    Connection conn = null;
    PreparedStatement pre = null;
    ResultSet res = null;
    @Override
    public List<UserInfo> GetAll() {
        try {
            conn = FactoryDB.GetConnection();
            pre = conn.prepareStatement("select * from userinfo");
            res = pre.executeQuery();
            List<UserInfo> list = new LinkedList<UserInfo>();
            while (res.next()) {
                list.add(new UserInfo(
                        res.getInt(1),
                        res.getDate(2),
                        res.getString(3),
                        res.getString(4)
                ));
            }
            FactoryDB.Close(conn, pre, res);
            return list;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
    @Override
    public boolean InsertUserInfo(UserInfo info) {
        try {
            conn = FactoryDB.GetConnection();
            pre = conn.prepareStatement("INSERT INTO userinfo VALUES (0,NOW(),?,?);");
            pre.setString(1, info.getUserName());
            pre.setString(2, info.getIntroduce());
            int isf = pre.executeUpdate();
            FactoryDB.Close(conn, pre, res);
            return isf != -1;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
    @Override
    public UserInfo SelectById(int id) {
        try {
            conn = FactoryDB.GetConnection();
            pre = conn.prepareStatement("select * from userinfo where id=?");
            pre.setInt(1, id);
            res = pre.executeQuery();
            //判断查询结果是否为空
            if (res.wasNull()) {
                return null;
            }
            UserInfo u=null;
            while (res.next()) {
                u = new UserInfo(res.getInt(1), res.getDate(2), res.getString(3), res.getString(4));
            }
            FactoryDB.Close(conn, pre, res);
            return u;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
    @Override
    public boolean UpdateById(UserInfo info) {
        try {
            conn = FactoryDB.GetConnection();
            pre = conn.prepareStatement("update userinfo set userName=?,introduce=? where id=?");
            pre.setString(1, info.getUserName());
            pre.setString(2, info.getIntroduce());
            pre.setInt(3, info.getId());
            int isf = pre.executeUpdate();
            FactoryDB.Close(conn, pre, res);
            return isf != -1;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
    @Override
    public boolean DeleteById(int id) {
        try {
            conn = FactoryDB.GetConnection();
            pre = conn.prepareStatement("delete from test.userinfo where id=?");
            pre.setInt(1, id);
            int isf = pre.executeUpdate();
            FactoryDB.Close(conn, pre, res);
            return isf != -1;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }
}