[原创]Spring Boot + Mybatis 简易使用指南（一）基础环境搭建

前言

作者: Ant QQ:517377100

相对于使用JdbcTemplate，Mybatis可自动建立pojo类型与数据库列的映射关系，数据库访问层的开发简单了许多

所有数据库访问操作，均封装在各个Mapper接口中，接口的实现即为数据库sql操作，sql可以注解的形式提供，也可以定义在xml文件中（复杂的sql操作优选xml）

引入Mybatis框架步骤简单，这里做一些整理

本人集成开发环境使用 Intellij

添加Mybatis依赖项

pom.xml增加如下依赖项

    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.2.8</version>
    </dependency>

    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis-spring</artifactId>
        <version>1.2.2</version>
    </dependency>

Bean声明

相关Bean的声明统一在DatabaseConfiguration类型中

其中包含了UserMapper、CommodityMapper、CommodityCategoryMapper三个Bean的声明

代码如下

@Configuration
public class DatabaseConfiguration {
    @Bean
    public DataSource dataSource() {
        ...
    }

	@Bean
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(dataSource());
        sqlSessionFactoryBean.setTypeAliases(new Class[]{User.class, Commodity.class, CommodityCategory.class});
        sqlSessionFactoryBean.getObject().getConfiguration().setMapUnderscoreToCamelCase(true);
        return sqlSessionFactoryBean.getObject();
    }

    private <T> MapperFactoryBean getMapper(Class<T> mapperInterface) {
        MapperFactoryBean<T> mapperFactoryBean = new MapperFactoryBean<T>();
        try {
            mapperFactoryBean.setSqlSessionFactory(sqlSessionFactory());
            mapperFactoryBean.setMapperInterface(mapperInterface);
        } catch (Exception ex) {
            logger.error("error when create mapper: ", ex);
            throw new RuntimeException(ex);
        }
        return mapperFactoryBean;
    }

    @Bean
    public MapperFactoryBean userMapper() {
        return getMapper(UserMapper.class);
    }

    @Bean
    public MapperFactoryBean commodityCategoryMapper() {
        return getMapper(CommodityCategoryMapper.class);
    }

    @Bean
    public MapperFactoryBean commodityMapper() {
        return getMapper(CommodityMapper.class);
    }
}

创建SqlSessionFactory的同时，将其配置项MapUnderscoreToCamelCase设置为true，如数据库列 user_name将自动映射到pojo中的userName属性

通过setTypeAliases，指定使用的Pojo类型，后续Mapper.xml中就不需要指定Pojo类型的完整限定名（即无需指定namespace）

Mapper interface

package com.antsoft.docoding.mapper;
import java.util.List;
import com.antsoft.docoding.model.User;

public interface UserMapper {
    List<User> getUsers();

    User getUser(long id);

    void addUser(User user);

    void clear();

    void updateUser(User user);
}

Mapper xml

Mapper.xml所在目录需要与对应的Mapper接口位于统一个包中

上述UserMapper接口，对应的UserMapper.xml 位于目录resources/com/antsoft/docoding/mapper/中，内容如下

<?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="com.antsoft.docoding.mapper.UserMapper">
    <resultMap id="user" type="user">
        <result column="user_type" property="userType" typeHandler="org.apache.ibatis.type.EnumOrdinalTypeHandler"/>
    </resultMap>
    
    <delete id="clear">
        DELETE FROM dc_user
    </delete>

    <select id="getUsers" resultMap="user">
        SELECT id, user_name, user_type FROM dc_user
    </select>

    <select id="getUser"  resultMap="user">
        SELECT id, user_name, user_type FROM dc_user WHERE id = #{id}
    </select>

    <insert id="addUser" useGeneratedKeys="true" keyProperty="id" parameterType="user">
        INSERT INTO dc_user(user_name, user_type)
        VALUES(#{userName}, #{userType, typeHandler=org.apache.ibatis.type.EnumOrdinalTypeHandler})
    </insert>

    <update id="updateUser" parameterType="user">
        UPDATE dc_user SET user_name = #{userNmae},
        user_type = #{userType, typeHandler=org.apache.ibatis.type.EnumOrdinalTypeHandler}
        WHERE id = #{id}
    </update>

</mapper>

关于EnumOrdinalTypeHandler，可以完成枚举值叙述与枚举类型的自动转换

使用Mapper

使用Mapper的方式与以前使用Dao类型的方法完全一致，通过@Autowired实现依赖注入，如下：

@Service
public class UserService {
    @Autowired
    private UserMapper userMapper;

    public void clear() {
        userMapper.clear();
    }

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

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

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

    public User getUser(long id) {
        return userMapper.getUser(id);
    }
}

更多Mabatis内容 请阅读官方文档

入门

动态SQL 简化工作