DAO接口及实现类

DAO接口中定义了所有的用户操作，如添加记录、删除记录及查询记录。

package chapter13;
import java.util.*;
public interface UserDAO {
    public void insert(User user) throws Exception;
    public void update(User user) throws Exception;
    public void delete(int userid) throws Exception;
    public User queryById(int userid) throws Exception;
    public List<User> queryAll() throws Exception;
}

DAO实现类实现了DAO接口，并且实现了接口中定义的所有方法。

package chapter13;

import java.util.*;
import java.sql.*;
import java.sql.Date;

public class UserDAOImpl implements UserDAO {

    @Override
    public void insert(User user) throws Exception {
        // TODO Auto-generated method stub
        String sql="insert into user(username,password) values(?,?)";
        PreparedStatement preparedStatement=null;
        DataBaseConnection dbc=null;
        try{
            dbc=new DataBaseConnection();
            preparedStatement=dbc.getConnection().prepareStatement(sql);
            preparedStatement.setString(1, user.getUserName());
            preparedStatement.setString(2, user.getPassword());
            preparedStatement.executeUpdate();
            preparedStatement.close();
        }
        catch(Exception e){
            throw new Exception("操作出现异常");
        }finally {
            dbc.close();
        }

    }

    @Override
    public void update(User user) throws Exception {
        // TODO Auto-generated method stub
        String sql="update user set username=?,password=? where userid=?";
        PreparedStatement preparedStatement=null;
        DataBaseConnection dbc=null;
        try{
            dbc=new DataBaseConnection();
            preparedStatement=dbc.getConnection().prepareStatement(sql);
            preparedStatement.setString(1, user.getUserName());
            preparedStatement.setString(2, user.getPassword());
            preparedStatement.setInt(3, user.getUserId());
            preparedStatement.executeUpdate();
            preparedStatement.close();
        }
        catch(Exception e){
            throw new Exception("操作出现异常");
        }finally {
            dbc.close();
        }
    }

    @Override
    public void delete(int userid) throws Exception {
        // TODO Auto-generated method stub
        String sql="delete from user where userid=?";
        PreparedStatement preparedStatement=null;
        DataBaseConnection dbc=null;
        try{
            dbc=new DataBaseConnection();
            preparedStatement=dbc.getConnection().prepareStatement(sql);
            preparedStatement.setInt(1, userid);
            preparedStatement.executeUpdate();
            preparedStatement.close();
        }
        catch(Exception e){
            throw new Exception("操作出现异常");
        }finally {
            dbc.close();
        }
    }

    @Override
    public User queryById(int userid) throws Exception {
        // TODO Auto-generated method stub
        User user=null;
        String sql="select * from user where userid=?";
        PreparedStatement preparedStatement=null;
        DataBaseConnection dataBaseConnection=null;
        try{
            dataBaseConnection=new DataBaseConnection();
            preparedStatement=dataBaseConnection.getConnection().prepareStatement(sql);
            ResultSet rSet=preparedStatement.executeQuery();
            if(rSet.next()){
                user=new User();
                user.setUserId(rSet.getInt(1));
                user.setUserName(rSet.getString(2));
                user.setPassword(rSet.getString(3));
            }
            rSet.close();
            preparedStatement.close();
        }
        catch(Exception e){
            throw new Exception("操作出现异常");
        }finally {
            dataBaseConnection.close();
        }
        return user;
    }

    @Override
    public List<User> queryAll() throws Exception {
        // TODO Auto-generated method stub
        List<User> all=new ArrayList<User>();
        String sql="select * from user";
        PreparedStatement preparedStatement=null;
        DataBaseConnection dataBaseConnection=null;
        try{
            dataBaseConnection=new DataBaseConnection();
            preparedStatement=dataBaseConnection.getConnection().prepareStatement(sql);
            ResultSet rSet=preparedStatement.executeQuery();
            if(rSet.next()){
                User user=new User();
                user=new User();
                user.setUserId(rSet.getInt(1));
                user.setUserName(rSet.getString(2));
                user.setPassword(rSet.getString(3));
                all.add(user);
            }
            rSet.close();
            preparedStatement.close();
        }
        catch(Exception e){
            throw new Exception("操作出现异常");
        }finally {
            dataBaseConnection.close();
        }
        return all;
    }

}