Mybatis 传统 DAO 层开发[了解]

朱雀 2022-12-23 06:26 214阅读 0赞

使用 Mybatis 开发 Dao，通常有两个方法，即原始 Dao 开发方式和 Mapper 接口代理开发方式。而现在主流的开发方式是接口代理开发方式，这种方式总体上更加简便。我们的课程讲解也主要以接口代理开发方式为主。在第二章节已经给大家介绍了基于代理方式的 dao 开发，现在给大家介绍一下基于传统编写 Dao 实现类的开发方式。

### **Mybatis 实现 DAO 的传统开发方式** ###

#### **1 持久层 Dao 接口** ####

/\*\*

\* <p>Title: IUserDao</p>

\* <p>Description: 用户的业务层接口</p>

\* <p>Company: http://www.itheima.com/ </p>

\*/

public interface IUserDao \{

/\*\*

\* 查询所有用户

\* @return

\*/

List<User> findAll();

/\*\*

\* 根据 id 查询

\* @param userId

\* @return

\*/

User findById(Integer userId);

/\*\*

\* 保存用户

\* @param user

\* @return 影响数据库记录的行数

\*/

int saveUser(User user);

/\*\*

\* 更新用户

\* @param user

\* @return 影响数据库记录的行数

\*/

int updateUser(User user);

/\*\*

\* 根据 id 删除用户

\* @param userId

\* @return

\*/

int deleteUser(Integer userId);

/\*\*

\* 查询总记录条数

\* @return

\*/

int findTotal();

#### **2 持久层 Dao 实现类** ####

/\*\*

\* <p>Title: UserDaoImpl</p>

\* <p>Description: dao 的实现类</p>

\* <p>Company: http://www.itheima.com/ </p>

\*/

public class UserDaoImpl implements IUserDao \{

private SqlSessionFactory factory;

public UserDaoImpl(SqlSessionFactory factory) \{

this.factory = factory;

@Override

public List<User> findAll() \{

SqlSession session = factory.openSession();

List<User> users = session.selectList("com.itheima.dao.IUserDao.findAll");

session.close();

return users;

@Override

public User findById(Integer userId) \{

SqlSession session = factory.openSession();

User user = session.selectOne("com.itheima.dao.IUserDao.findById",userId);

session.close();

return user;

@Override

public int saveUser(User user) \{

SqlSession session = factory.openSession();

int res = session.insert("com.itheima.dao.IUserDao.saveUser",user);

session.commit();

session.close();

return res;

@Override

public int updateUser(User user) \{

SqlSession session = factory.openSession();

int res = session.update("com.itheima.dao.IUserDao.updateUser",user);

session.commit();

session.close();

return res;

@Override

public int deleteUser(Integer userId) \{

SqlSession session = factory.openSession();

int res = session.delete("com.itheima.dao.IUserDao.deleteUser",userId);

session.commit();

session.close();

return res;

@Override

public int findTotal() \{

SqlSession session = factory.openSession();

int res = session.selectOne("com.itheima.dao.IUserDao.findTotal");

session.close();

return res;

#### **3 持久层映射配置** ####

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper

PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

select \* from user

</select>

<select id="findById" resultType="com.itheima.domain.User"

parameterType="int">

select \* from user where id = \#\{uid\}

</select>

<!-- 保存用户

ognl 表达式：它是 apache 提供的一种表达式语言，在 struts2 中也有应用。

Object Graphic Navigation Language 对象图导航语言

它是按照一定的语法格式来获取数据的。

语法格式就是使用 \#\{对象.对象\}的方式

\#\{user.username\}它会先去找 user 对象，然后在 user 对象中找到 username 属性，并把值取

出来

\-->

select last\_insert\_id();

</selectKey>

insert into user(username,birthday,sex,address)

values(\#\{username\},\#\{birthday\},\#\{sex\},\#\{address\})

</insert>

update user set

username=\#\{username\},birthday=\#\{birthday\},sex=\#\{sex\},address=\#\{address\} where

id=\#\{id\}

</update>

delete from user where id = \#\{uid\}

</delete>

select count(\*) from user;

</select>

</mapper>

#### **4 测试类** ####

/\*\*

\* <p>Title: MybastisCRUDTest</p>

\* <p>Description: 测试 mybatis 的 crud 操作</p>

\* <p>Company: http://www.itheima.com/ </p>

\*/

public class MybastisCRUDTest \{

private InputStream in ;

private SqlSessionFactory factory;

private IUserDao userDao;

@Test

public void testFindAll() \{

List<User> users = userDao.findAll();

for(User user : users) \{

System.out.println(user);

@Test

public void testFindOne() \{

//6.执行操作

User user = userDao.findById(56);

System.out.println(user);

@Test

public void testSaveUser() throws Exception \{

User user = new User();

user.setUsername("mybatis dao user");

//6.执行操作

int res = userDao.saveUser(user);

System.out.println(res);

System.out.println(user.getId());

@Test

public void testUpdateUser()throws Exception\{

//1.根据 id 查询

User user = userDao.findById(41);

//2.更新操作

user.setAddress("北京市顺义区");

int res = userDao.updateUser(user);

System.out.println(res);

@Test

public void testDeleteUser() throws Exception \{

//6.执行操作

int res = userDao.deleteUser(56);

System.out.println(res);

@Test

public void testFindTotal() throws Exception \{

//6.执行操作

int res = userDao.findTotal();

System.out.println(res);

@Before//在测试方法执行之前执行

public void init()throws Exception \{

//1.读取配置文件

in = Resources.getResourceAsStream("SqlMapConfig.xml");

//2.创建构建者对象

SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();

//3.创建 SqlSession 工厂对象

factory = builder.build(in);

//4.创建 Dao 接口的实现类

userDao = new UserDaoImpl(factory);

@After//在测试方法执行完成之后执行

public void destroy() throws Exception\{

//7.释放资源

in.close();

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