Spring-Mybatis的业务实现的几种方式

叁歲伎倆 2021-08-28 12:28 239阅读 0赞

## Spring-Mybatis的业务实现的三种方式 ##

### 1、新建Maven项目 ###

### 2、导入依赖 ###

<dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.23</version>
    </dependency>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.4</version>
    </dependency>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis-spring</artifactId>
      <version>1.3.1</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-jdbc</artifactId>
      <version>5.0.8.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>5.0.8.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>5.0.8.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-test</artifactId>
      <version>5.0.8.RELEASE</version>
    </dependency>

### 3、对应数据库建立实体类 ###

![在这里插入图片描述][20200429230257651.png]

无参构造函数、getter和setter还有toString方法

User.java：

@Component
    public class User { 
        private int uid;
        private String username;
        private String password;
        private int age;
    
        public User() { 
        }
    
        @Override
        public String toString() { 
            return "User{" +
                    "uid=" + uid +
                    ", username='" + username + '\'' +
                    ", password='" + password + '\'' +
                    ", age=" + age +
                    '}';
        }
    
        public int getUid() { 
            return uid;
        }
    
        public void setUid(int uid) { 
            this.uid = uid;
        }
    
        public String getUsername() { 
            return username;
        }
    
        public void setUsername(String username) { 
            this.username = username;
        }
    
        public String getPassword() { 
            return password;
        }
    
        public void setPassword(String password) { 
            this.password = password;
        }
    
        public int getAge() { 
            return age;
        }
    
        public void setAge(int age) { 
            this.age = age;
        }
    }

### 4、编写Mapper接口 ###

完成CRUD（增删改查）的需求

UserMapper.java：

public interface UserMapper { 
        //查询所有用户
        List<User> selectAllUser();
        //根据id查询用户
        User selectUserById(int uid);
        //根据username模糊查询
        List<User> selectUserLikeUsername(String username);
        //新增用户（主键自增）
        int insertUser(User user);
    }

### 5、编写Mapper接口对应的Mapper.xml文件 ###

**强烈建议**Mapper接口文件和Mapper.xml文件在同一个包下

`<namespace>`对应接口的类限定名

对应的CRUD的标签的id对应Mapper接口的方法名字，返回值和传入参数也要对应

UserMapper.xml

<?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">
    <mapper namespace="cn.yznu.mapper.UserMapper">
        <select id="selectAllUser" resultType="User">
            SELECT
                *
            FROM
                user
        </select>
        <select id="selectUserById" parameterType="integer" resultType="User">
            SELECT
                *
            FROM
                user
            WHERE
                uid=#{uid}
        </select>
        <select id="selectUserLikeUsername" parameterType="string" resultType="User">
            SELECT
                *
            FROM
                user
            WHERE
                username LIKE "%"#{username}"%"
        </select>
        <insert id="insertUser" parameterType="User" keyProperty="uid" useGeneratedKeys="true">
            INSERT INTO
                user
            (username,password,age)
            VALUES
            (#{username},#{password},#{age})
        </insert>
    </mapper>

### 6、properties属性文件 ###

db.properties:

jdbc.driver=com.mysql.jdbc.Driver
    jdbc.url=jdbc:mysql://localhost:3306/表名?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8
    jdbc.username=数据库用户名
    jdbc.password=数据库密码

### 7、mybatis-config配置文件 ###

mybatis-config.xml：

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
        <typeAliases>
            <package name="cn.yznu.pojo" />
        </typeAliases>
        <mappers>
            <mapper class="cn.yznu.mapper.UserMapper"/>
        </mappers>
    </configuration>

### 8、spring-dao配置文件（建议单独写，再丢入Spring容器） ###

spring-config.xml：

<?xml version="1.0" encoding="UTF-8"?>
    <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
        
        <context:property-placeholder location="classpath:db.properties"/>
        
        <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
            <property name="driverClassName" value="${jdbc.driver}"/>
            <property name="url" value="${jdbc.url}"/>
            <property name="username" value="${jdbc.username}"/>
            <property name="password" value="${jdbc.password}"/>
        </bean>
        
        <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
            <property name="dataSource" ref="dataSource"/>
            <property name="configLocation" value="classpath:mybatis-config.xml"/>
        </bean>
        
        <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
            <constructor-arg index="0" ref="sqlSessionFactory"/>
        </bean>
    </beans>

### 9、Spring容器配置文件 ###

applicationContext.xml：

### 10、编写Mapper接口的实现类 ###

写实现类的目的就是为了先将sqlSession对象获取到，然后再将SqlSession对象跟Mapper接口的CRUD方法**封装**，避免以后在业务里每次都还需要去获取SqlSession对象。

#### 第一种方式、用@Autowired自动装配SqlSession对象 ####

##### UserMapperImpl.java： #####

public class UserMapperImpl implements UserMapper { 
        @Autowired
        SqlSession sqlSession;
        @Override
        public List<User> selectAllUser() { 
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            return mapper.selectAllUser();
        }
    
        @Override
        public User selectUserById(int uid) { 
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            return mapper.selectUserById(uid);
        }
    
        @Override
        public List<User> selectUserLikeUsername(String username) { 
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            return mapper.selectUserLikeUsername(username);
        }
    
        @Override
        public int insertUser(User user) { 
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            return mapper.insertUser(user);
        }
    }

##### 然后再给UserMapper接口和UserMapperImpl实现类的头上添加`@component`注解并且在spring容器里添加component扫描，让spring能够托管它们： #####

@Component
    public interface UserMapper {

@Component
    public class UserMapperImpl implements UserMapper {

##### 测试： #####

UserMapperTest.java：

@RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration(locations = { "/applicationContext.xml"})
    public class UserMapperTest { 
        @Autowired
        UserMapper userMapper;
        @Autowired
        User user;
        @Test
        public void selectAllUser() { 
            List<User> userList = userMapper.selectAllUser();
            System.out.println(userList);
        }
    
        @Test
        public void selectUserById() { 
            User user = userMapper.selectUserById(1);
            System.out.println(user);
        }
    
        @Test
        public void selectUserLikeUsername() { 
            List<User> userList = userMapper.selectUserLikeUsername("q");
            System.out.println(userList);
        }
    
        @Test
        public void insertUser() { 
            user.setUsername("测试");
            userMapper.insertUser(user);
        }
    }

因为UserMapper的接口和它的实现还有User都被我们丢到了spring容器，所以用`@Autowired`就可以直接用了，同时因为UserMapperImpl里面我们已经将sqlSession跟CRUD封装起来了，所以在测试里就不需要获取sqlSession对象了。

##### 总结：在接口的实现类里，用Autowired获取到sqlSession对象，再返回sqlSession.getMapper()里的相应方法 #####

#### 第二种方式、在实现里用SqlSessionTemplate获取到sqlSess对象 ####

去掉刚刚给UserMapper和UserMapperImpl头上加的@Component注解

再把刚刚的UserMapperImpl.java改成这样：

public class UserMapperImpl implements UserMapper { 
        private SqlSessionTemplate sqlSession;
        public void setSqlSession(SqlSessionTemplate sqlSession){ 
            this.sqlSession=sqlSession;
        }
        @Override
        public List<User> selectAllUser() { 
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            return mapper.selectAllUser();
        }
    
        @Override
        public User selectUserById(int uid) { 
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            return mapper.selectUserById(uid);
        }
    
        @Override
        public List<User> selectUserLikeUsername(String username) { 
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            return mapper.selectUserLikeUsername(username);
        }
    
        @Override
        public int insertUser(User user) { 
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            return mapper.insertUser(user);
        }
    }

用SqlSessionTemplate获取sqlSession对象，再写一个setSqlSession方法

再到applicationContext容器里给这个setSqlSession注入SqlSession：

去掉刚刚的`<context:component-scan base-package="cn.yznu.mapper"/>`

测试：

UserMapperTest.java:

@RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration(locations = { "/applicationContext.xml"})
    public class UserMapperTest { 
        @Autowired
        UserMapper userMapper;
        @Autowired
        User user;
        @Test
        public void selectAllUser() { 
            List<User> userList = userMapper.selectAllUser();
            System.out.println(userList);
        }
    
        @Test
        public void selectUserById() { 
            User user = userMapper.selectUserById(1);
            System.out.println(user);
        }
    
        @Test
        public void selectUserLikeUsername() { 
            List<User> userList = userMapper.selectUserLikeUsername("q");
            System.out.println(userList);
        }
    
        /*@Test public void insertUser() { user.setUsername("测试"); userMapper.insertUser(user); }*/
    }

因为刚刚我们的UserMapperImpl里已经跟SqlSession封装好了，并且也在applicationContext容器中注入了，所以我们就可以直接在业务或者测试里面直接用@Autowired自动装配UserMapper对象了。

#### 第三种方式、用实现类继承SqlSessionSupport类再获取sqlSession对象 ####

继承SqlSessionSupport类之后，就可以直接使用getSqlSession()方法获得sqlSession对象了

public class UserMapperImpl extends SqlSessionDaoSupport implements UserMapper  { 
        @Override
        public List<User> selectAllUser() { 
            UserMapper mapper = getSqlSession().getMapper(UserMapper.class);
            return mapper.selectAllUser();
        }
    
        @Override
        public User selectUserById(int uid) { 
            UserMapper mapper = getSqlSession().getMapper(UserMapper.class);
            return mapper.selectUserById(uid);
        }
    
        @Override
        public List<User> selectUserLikeUsername(String username) { 
            UserMapper mapper = getSqlSession().getMapper(UserMapper.class);
            return mapper.selectUserLikeUsername(username);
        }
    
        @Override
        public int insertUser(User user) { 
            UserMapper mapper = getSqlSession().getMapper(UserMapper.class);
            return mapper.insertUser(user);
        }
    }

要在Spring容器里给UserMapper注入SqlSessionFactory

applicationContext.xml：

测试：

UserMapperTestjava

@RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration(locations = { "/applicationContext.xml"})
    public class UserMapperTest { 
        @Autowired
        UserMapper userMapper;
        @Autowired
        User user;
        @Test
        public void selectAllUser() { 
            List<User> userList = userMapper.selectAllUser();
            System.out.println(userList);
        }
    
        @Test
        public void selectUserById() { 
            User user = userMapper.selectUserById(1);
            System.out.println(user);
        }
    
        @Test
        public void selectUserLikeUsername() { 
            List<User> userList = userMapper.selectUserLikeUsername("q");
            System.out.println(userList);
        }
    
        /*@Test public void insertUser() { user.setUsername("测试"); userMapper.insertUser(user); }*/
    }

由于我们在实现类里继承了sqlSessionSupport类然后调用getSqlSession()方法获取到了sqlSession对象，并且在Spring容器里也注入了SqlSessionFactory，所以我们就可以直接在测试或者业务里用@Autowired装配UserMapper对象

其中，第二种方式和第三种方式都是官网提到的方式，官网更推荐第三种：

http://mybatis.org/spring/zh/sqlsession.html

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTc0NzA4MA_size_16_color_FFFFFF_t_70]

## 总结： ##

都是为了解耦而将sqlSession跟Mapper接口的CRUD封装，然后交给Spring容器管理，再在业务或者测试里用@Autowired自动装配就好了

[20200429230257651.png]: /images/20210813/bd1584e3dfb8452f8c967bb5d9a17181.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NTc0NzA4MA_size_16_color_FFFFFF_t_70]: /images/20210813/d0bb22dd66ff4a92ba39334ff46e7fdf.png