基于MyBatis的简单使用(推荐)

下面就给您详细讲解“基于MyBatis的简单使用(推荐)”。

什么是MyBatis?

MyBatis是一款基于Java语言的开源持久层框架，它是面向SQL的框架，并且可以轻松地与各种数据源进行集成。它的主要特点是使得数据持久化开发变得更加容易，开发者只需要编写简单的SQL语句，而且框架还为开发者提供了便捷的ORM操作。

MyBatis的简单使用

下面我们来演示一下如何在Java项目中使用MyBatis。

1. 首先需要引入MyBatis的相关依赖，常用的有以下五个：

<!--MyBatis核心依赖-->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.7</version>
</dependency>
<!--MyBatis与Spring集成依赖-->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-spring</artifactId>
    <version>2.0.6</version>
</dependency>
<!--数据库连接池依赖-->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.2.2</version>
</dependency>
<!--数据库驱动依赖-->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.22</version>
</dependency>
<!--日志依赖-->
<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-log4j12</artifactId>
    <version>1.7.25</version>
</dependency>

1. 在项目的配置文件中配置数据库连接、MyBatis与Spring的集成、Mapper的扫描等信息。

<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
    <property name="url" value="${jdbc.url}" />
    <property name="username" value="${jdbc.username}" />
    <property name="password" value="${jdbc.password}" />
    <property name="initialSize" value="1" />
    <property name="maxActive" value="20" />
    <property name="maxWait" value="60000" />
    <property name="timeBetweenEvictionRunsMillis" value="60000" />
    <property name="minEvictableIdleTimeMillis" value="300000" />
    <property name="validationQuery" value="SELECT 'x'" />
    <property name="testWhileIdle" value="true" />
    <property name="testOnBorrow" value="false" />
    <property name="testOnReturn" value="false" />
    <property name="poolPreparedStatements" value="true" />
    <property name="maxPoolPreparedStatementPerConnectionSize" value="20" />
    <property name="filters" value="mergeStat" />
</bean>

<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="typeAliasesPackage" value="com.example.model" />
    <property name="mapperLocations" value="classpath:mapper/*.xml" />
</bean>

<bean id="sqlSessionTemplate" class="org.mybatis.spring.SqlSessionTemplate">
    <constructor-arg name="sqlSessionFactory" ref="sqlSessionFactory" />
</bean>

<!--扫描MyBatis Mapper-->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="basePackage" value="com.example.mapper" />
</bean>

1. 编写Mapper接口，用于执行SQL语句。

public interface UserMapper {

    @Select("select * from t_user where id = #{id}")
    User selectById(Long id);

    @Select("select * from t_user")
    List<User> selectAll();

    @Insert("insert into t_user(username, password) values(#{username}, #{password})")
    int insert(User user);

    @Update("update t_user set username = #{username}, password = #{password} where id = #{id}")
    int update(User user);

    @Delete("delete from t_user where id = #{id}")
    int deleteById(Long id);

}

1. 编写Mapper映射文件，用于描述SQL语句的具体内容。

<mapper namespace="com.example.mapper.UserMapper">

    <resultMap id="userMap" type="com.example.model.User">
        <id property="id" column="id" />
        <result property="username" column="username" />
        <result property="password" column="password" />
        <result property="createTime" column="create_time" />
        <result property="updateTime" column="update_time" />
    </resultMap>

    <select id="selectById" resultMap="userMap">
        select * from t_user where id = #{id}
    </select>

    <select id="selectAll" resultMap="userMap">
        select * from t_user
    </select>

    <insert id="insert">
        insert into t_user(username, password) values(#{username}, #{password})
    </insert>

    <update id="update">
        update t_user set username = #{username}, password = #{password} where id = #{id}
    </update>

    <delete id="deleteById">
        delete from t_user where id = #{id}
    </delete>

</mapper>

1. 编写Service层，调用Mapper接口执行SQL语句，并包装返回的结果。

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public User selectById(Long id) {
        return userMapper.selectById(id);
    }

    public List<User> selectAll() {
        return userMapper.selectAll();
    }

    public void insert(User user) {
        userMapper.insert(user);
    }

    public void update(User user) {
        userMapper.update(user);
    }

    public void deleteById(Long id) {
        userMapper.deleteById(id);
    }

}

1. 编写Controller层，对外提供接口。

@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping("/{id}")
    public User selectById(@PathVariable Long id) {
        return userService.selectById(id);
    }

    @GetMapping("")
    public List<User> selectAll() {
        return userService.selectAll();
    }

    @PostMapping("")
    public void insert(@RequestBody User user) {
        userService.insert(user);
    }

    @PutMapping("")
    public void update(@RequestBody User user) {
        userService.update(user);
    }

    @DeleteMapping("/{id}")
    public void deleteById(@PathVariable Long id) {
        userService.deleteById(id);
    }

}

示例

下面给出基于MyBatis的两个示例。

1. 查询用户信息

用户信息在t_user表中，包含id, username, password, create_time, update_time五个字段。根据用户id查询其信息。

public interface UserMapper {

    @Select("select * from t_user where id = #{id}")
    User selectById(Long id);

}

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public User selectById(Long id) {
        return userMapper.selectById(id);
    }

}

@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping("/{id}")
    public User selectById(@PathVariable Long id) {
        return userService.selectById(id);
    }

}

1. 新增用户信息

用户信息需要新增到t_user表中，包含id, username, password, create_time, update_time五个字段。需要通过Spring MVC接收用户提交的数据，并将数据保存到数据库。

public interface UserMapper {

    @Insert("insert into t_user(username, password, create_time, update_time) values(#{username}, #{password}, #{createTime}, #{updateTime})")
    int insert(User user);

}

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public void insert(User user) {
        user.setCreateTime(new Date());
        user.setUpdateTime(new Date());
        userMapper.insert(user);
    }

}

@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserService userService;

    @PostMapping("")
    public void insert(@RequestBody User user) {
        userService.insert(user);
    }

}