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;
     }

 }