1.整合MyBatis操作
前面一篇提到了SpringBoot整合基础的数据源JDBC、Druid操作，实际项目中更常用的还是MyBatis框架，而SpringBoot整合MyBatis进行CRUD也非常方便。
下面从配置模式、注解模式、混合模式三个方面进行说明MyBatis与SpringBoot的整合。
1.1.配置模式
MyBatis配置模式是指使用mybatis配置文件的方式与SpringBoot进行整合，相对应的就有mybatis-config.xml（用于配置驼峰命名，也可以省略这个文件）、XxxMapper.xml文件。
主要步骤为：
- 导入mybatis官方starter
- 编写mapper接口。标准@Mapper注解
- 编写sql映射文件并绑定mapper接口
在application.yaml中指定Mapper配置文件的位置，以及指定全局配置文件的信息 （建议；配置在mybatis.configuration中，可以省略mybatis-config.xml文件）
下面是具体整合配置步骤：
①引入相关依赖pom.xml配置：
pom.xml
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--整合mybatis-->
<dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>2.1.4</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<scope>runtime</scope>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
</plugins>
</build>②编写对应Mapper接口：
@Mapper //这个注解表示了这个类是一个mybatis的mapper接口类
@Repository
public interface UserMapper {
//@Select("select * from user")
List<User> findAllUsers();
//@Insert("insert into user(id, username, password) values (#{id}, #{username}, #{password})")
void insert(User user);
//@Update("update user set username = #{username}, password = #{password} where id = #{id}")
void update(User user);
//@Delete("delete from user where id = #{id}")
void deleteById(Integer id);
}③在resources下创建对应的mapper文件，对应domain类，数据库表单如下：
User类：
@Data
public class User {
private Integer id;
private String username;
private String password;
}数据库user表：
UserMapper.xml文件：
<?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">
<!--namespace表示当前mapper的唯一标识：一般使用domain的全路径名+Mapper来命名-->
<mapper namespace="com.fengye.springboot_mybatis.mapper.UserMapper">
<!--id：方法表示，一般配置对应的方法；
resultType：表示该方法有返回，返回需要封装到对应实体的类型-->
<select id="findAllUsers" resultType="com.fengye.springboot_mybatis.entity.User">
select * from user
</select>
<insert id="insert" parameterType="com.fengye.springboot_mybatis.entity.User">
insert into user(id, username, password) values (#{id}, #{username}, #{password})
</insert>
<update id="update" parameterType="com.fengye.springboot_mybatis.entity.User">
update user set username = #{username}, password = #{password} where id = #{id}
</update>
<delete id="deleteById" parameterType="Integer">
delete from user where id = #{id}
</delete>
</mapper>④对应配置application.yml文件：
application.yml
server:
port: 8083
spring:
datasource:
username: root
password: admin
#假如时区报错，增加时区配置serverTimezone=UTC
url: jdbc:mysql://localhost:3306/mybatis02_0322?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8
driver-class-name: com.mysql.cj.jdbc.Driver
mybatis:
#config-location: classpath:mybatis/mybatis-config.xml 使用了configuration注解则无需再指定mybatis-config.xml文件
mapper-locations: classpath:mybatis/mapper
@Insert("insert into city(name, state, country) values (#{name}, #{state}, #{country})")
@Options(useGeneratedKeys = true, keyProperty = "id")
public void insert(City city);
@Update("update city set name = #{name}, state = #{state}, country = #{country} where id = #{id}")
public void update(City city);
@Delete("delete from city where id = #{id}")
public void deleteById(Long id);
}③编写Service层、Controller层：
Service相关：
public interface CityService {
City findCityById(Long id);
void insert(City city);
void update(City city);
void deleteById(Long id);
}
@Service
public class CityServiceImpl implements CityService {
@Autowired
private CityMapper cityMapper;
@Override
public City findCityById(Long id) {
return cityMapper.getCityById(id);
}
@Override
public void insert(City city) {
cityMapper.insert(city);
}
@Override
public void update(City city) {
cityMapper.update(city);
}
@Override
public void deleteById(Long id) {
cityMapper.deleteById(id);
}
}Controller相关：
@RestController
@RequestMapping("/city/api")
public class CityController {
@Autowired
private CityService cityService;
@RequestMapping("/findCityById/{id}")
public City findCityById(@PathVariable("id") Long id){
return cityService.findCityById(id);
}
@PostMapping("/insert")
public String insert(City city){
cityService.insert(city);
return "insert ok";
}
@PostMapping("/update")
public String update(City city){
cityService.update(city);
return "update ok";
}
@GetMapping("/delete/{id}")
public String delete(@PathVariable("id") Long id){
cityService.deleteById(id);
return "delete ok";
}
}④对应使用Postman接口进行测试：
简单模拟接口POST/GET请求即可：
1.3.混合模式
在实际项目开发中涉及很多复杂业务及连表查询SQL，可以配合使用注解与配置模式，达到最佳实践的目的。
实际项目操作步骤：
- 引入mybatis-starter
- 配置application.yaml中，指定mapper-location位置即可
- 编写Mapper接口并标注@Mapper注解
- 简单方法直接注解方式
- 复杂方法编写mapper.xml进行绑定映射
- 主启动类上使用@MapperScan("com.fengye.springboot_mybatis.mapper") 简化Mapper接口，包下所有接口就可以不用标注@Mapper注解
具体配置如下：
@SpringBootApplication
//主启动类上标注，在XxxMapper中可以省略@Mapper注解
@MapperScan("com.fengye.springboot_mybatis.mapper")
public class SpringbootMybatisApplication {
public static void main(String[] args) {
SpringApplication.run(SpringbootMybatisApplication.class, args);
}
}
@Repository
public interface CityMapper {
@Select("select * from city where id = #{id}")
public City getCityById(Long id);
@Insert("insert into city(name, state, country) values (#{name}, #{state}, #{country})")
@Options(useGeneratedKeys = true, keyProperty = "id")
public void insert(City city);
@Update("update city set name = #{name}, state = #{state}, country = #{country} where id = #{id}")
public void update(City city);
@Delete("delete from city where id = #{id}")
public void deleteById(Long id);
}本博客参考写作文档：
SpringBoot2核心技术与响应式编程
博客涉及代码示例均已上传至github地址：
SpringBootStudy
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