24、springboot——整合Mybatis之Mybatis注解开发②

1、创建department的mapper（注解版）

//指定这是一个操作数据库的mapper
@Mapper
public interface DepartmentMapper {

    @Select("select * from department where id = #{id}")
    public Department getDeptById(Integer id);

    @Delete("delete from department where id = #{id}")
    public int deleteDeptById(Integer id);

    @Insert("insert into department(departmentName) values(#{departmentName})")
    public int insertDept(Department department);

    @Update("update department set departmentName=#{departmentName} where id=#{id}")
    public int updateDept(Department department);
}

2、创建department的controller（这里都是get请求，直接访问链接即可，为了方便测试）

@RestController
public class DeptController {

    @Autowired
    DepartmentMapper departmentMapper;

    @GetMapping("/dept/{id}")
    public Department getDepartment(@PathVariable("id") Integer id){
        return departmentMapper.getDeptById(id);
    }

    @GetMapping("/dept")
    public Department insertDept(Department department){
        departmentMapper.insertDept(department);
        return department;
    }
}

3、通过访问链接简单测试

　　插入成功

 　　查询成功

 4、解决插入成功后返回的id为null问题

　　

 　　修改department的mapper的插入方法；添加@Options(useGeneratedKeys = true,keyProperty = "id")配置，keyProperty的值是java类中主键的名称

        //配置@Options(useGeneratedKeys = true,keyProperty = "id")插入数据成功后可以的到插入时的id
        @Options(useGeneratedKeys = true,keyProperty = "id")
        @Insert("insert into department(departmentName) values(#{departmentName})")
        public int insertDept(Department department);

　　修改之后再插入数据就可以得到id了

 5、mybatis的通过配置类开启驼峰命名法

　　我们把数据库的里department表的departmentName字段名改为department_name

　　再测试查询的时候发现查询出的departmentName为null；说明springboot整合mybatis时mybatis的驼峰命名法默认是关闭的

 　　不用配置文件开启的话；需要创建Mybatis的配置类，即在容器中注册一个自定义配置类ConfigurationCustomizer 

　　　　

import org.mybatis.spring.boot.autoconfigure.ConfigurationCustomizer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class MybatisConfig {
    @Bean
    public ConfigurationCustomizer configurationCustomizer(){
        return new ConfigurationCustomizer() {
            @Override
            public void customize(org.apache.ibatis.session.Configuration configuration) {
                //开启驼峰命名法
                configuration.setMapUnderscoreToCamelCase(true);
            }
        };
    }
}

　　配置完成后再次访问链接可以看到departmentName的值取到了，说明驼峰命名法配置开启成功

 6、通过@MapperScan(value = "")配置代替@Mapper注解（即批量扫描mapper）

　　我们每写一个mapper映射接口都得加上@Mapper注解

　　

 　　如果mapper多了起来每次都得加上@Mapper这个注解会觉得麻烦；

　　这时只需要在配置类中（只要是加入到容器的配置类就行）加上@MapperScan(value = "")指定mapper的包路径，就不用每个mapper都得加@Mapper注解了　　

　　我们以把@MapperScan(value = "")加载mybatis的配置类为例：

@MapperScan(value = "com.atguigu.spring.mapper")
@Configuration
public class MybatisConfig {
    @Bean
    public ConfigurationCustomizer configurationCustomizer(){
        return new ConfigurationCustomizer() {
            @Override
            public void customize(org.apache.ibatis.session.Configuration configuration) {
                //开启驼峰命名法
                configuration.setMapUnderscoreToCamelCase(true);
            }
        };
    }
}

　　然后我们在注释掉mapper接口的@Mapper注解

 　　重启应用再次测试发现mapper依然映射成功：