Spring Boot学习笔记18——数据访问（整合mybatis）

1. 环境准备

1.1 创建项目

创建一个新的项目（选中web、jdbc、mysql和mybatis环境）
项目新增的mybatis依赖

<dependency>
       <groupId>org.mybatis.spring.bootgroupId>
       <artifactId>mybatis-spring-boot-starterartifactId>
       <version>2.1.3version>
dependency>

查看依赖树

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1.2 整合mybatis步骤

1. 配置数据源相关属性（详细见上一学习笔记Druid）

   • 加入依赖

     
     
     <dependency>
         <groupId>com.alibabagroupId>
         <artifactId>druidartifactId>
         <version>1.1.8version>
     dependency>
     

     如果后面启动有报log4j的错误，就加上log4j的依赖

     
     <dependency>
     	<groupId>log4jgroupId>
     	<artifactId>log4jartifactId>
     	<version>1.2.17version>
     dependency>
     

   • 配置yml

     spring:
     datasource:
     #   数据源基本配置
     username: root
     password: root
     driver-class-name: com.mysql.cj.jdbc.Driver
     url: jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC
     type: com.alibaba.druid.pool.DruidDataSource
     # 追加配置，使得这两个sql文件能顺利执行
     schema:
     - classpath:sql/department.sql
     - classpath:sql/employee.sql
     initialization-mode: always
     #springboot2.x以上需要加这一句配置，不然无法执行sql和建表
     
     #   数据源其他配置
     initialSize: 5
     minIdle: 5
     maxActive: 20
     maxWait: 60000
     timeBetweenEvictionRunsMillis: 60000
     minEvictableIdleTimeMillis: 300000
     validationQuery: SELECT 1 FROM DUAL
     testWhileIdle: true
     testOnBorrow: false
     testOnReturn: false
     poolPreparedStatements: true
     #   配置监控统计拦截的filters，去掉后监控界面sql无法统计，'wall'用于防火墙
     filters: stat,wall,log4j
     maxPoolPreparedStatementPerConnectionSize: 20
     useGlobalDataSourceStat: true
     connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500
     
     

   3. 创建数据源配置类

      @Configuration
      public class DruidConfig {
               
      
      @ConfigurationProperties(prefix = "spring.datasource")
      @Bean
      public DataSource druid(){
               
      	return  new DruidDataSource();
      }
      
      //配置Druid的监控
      //1、配置一个管理后台的Servlet
      @Bean
      public ServletRegistrationBean statViewServlet(){
               
      ServletRegistrationBean bean = new ServletRegistrationBean(new StatViewServlet(), "/druid/*");
      Map<String,String> initParams = new HashMap<>();
      
      initParams.put("loginUsername","admin");
      initParams.put("loginPassword","123456");
      initParams.put("allow","");//默认就是允许所有访问
      initParams.put("deny","192.168.15.21");
      
      bean.setInitParameters(initParams);
      return bean;
      }
      
      
       //2、配置一个web监控的filter
      @Bean
      public FilterRegistrationBean webStatFilter(){
               
      FilterRegistrationBean bean = new FilterRegistrationBean();
      bean.setFilter(new WebStatFilter());
      
      Map<String,String> initParams = new HashMap<>();
      initParams.put("exclusions","*.js,*.css,/druid/*");
      
      bean.setInitParameters(initParams);
      
      bean.setUrlPatterns(Arrays.asList("/*"));
      
      return  bean;
      	}
      }
      

2. 创建数据库
   

   copy两个sql语句到resources的sql文件夹中
   
   sql内容如下
   
   运行项目，见表成功
   

3. 创建JavaBean
   bean.Department
   
   bean.Employee
   然后把yml中的schema配置给注释掉

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2. 注解版mybatis

2.1 mybatis

1. 创建mapper.DepartmentMapper接口，写sql语句方法

   @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);
   
   @Options(useGeneratedKeys = true,keyProperty = "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);
   }
   

   @Options(useGeneratedKeys = true,keyProperty = "id")是为了获取自增的id

2. 创建控制器方法controller.DeptController

   @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. 启动项目，在浏览器进行添加操作
   
   添加成功
   

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2.2 自定义MyBatis的配置规则

如果我们把数据库中departmentName改成department_name，这时进行查询将无法读取部门们，这时候就需要我们给容器中添加一个ConfigurationCustomizer，来解决列名改成驼峰命名法而导致无法读取内容的问题

创建config.MyBatisConfig

@org.springframework.context.annotation.Configuration
public class MyBatisConfig {
     

    @Bean
    public ConfigurationCustomizer configurationCustomizer(){
     
        return new ConfigurationCustomizer(){
     

            @Override
            public void customize(Configuration configuration) {
     
                configuration.setMapUnderscoreToCamelCase(true);
            }
        };
    }
}

2.2.1 @MapperScan

注解版mybatis需要在每个mapper接口上添加@Mapper注解才能运行，但是我们直接在主启动类上添加 @MapperScan(value = "mapper接口所在的全限定名称包")，如@MapperScan(value="com.sb.mapper")，就可以省去给每个mapper接口写注解啦

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3. 配置版mybatis

1. 创建mapper接口mapper.EmployeeMapper

   public interface EmployeeMapper {
          //记得要用@Mapper或@MapperScan将接口扫描装配到容器中
   
   	public Employee getEmpById(Integer id);
   
   	public void insertEmp(Employee employee);
   }
   

2. 创建mapper映射文件和全局配置文件
   
   EmployeeMapper.xml

   <mapper namespace="com.sb.mapper.EmployeeMapper">
   
   <select id="getEmpById" resultType="com.sb.bean.Employee">
       SELECT * FROM employee WHERE id=#{id}
   select>
   
   <insert id="insertEmp">
       INSERT into employee(lastName,email,gender,d_id) values (#{lastName},#{email},#{gender},#	{dId})
   insert>
   
   mapper>
   

   mybatis-config.xml

   <configuration>
   
   <settings>
       <setting name="mapUnderscoreToCamelCase" value="true"/>
   settings>
       
   configuration>
   

3. 在yml追加mybatis配置

   mybatis:
   # 指定全局配置文件的位置
   config-location: classpath:mybatis/mybatis-config.xml
   # 指定sql映射文件的位置
   mapper-locations: classpath:mybatis/mapper/*.xml
   

4. 创建控制器方法controller.EmpController

   @RestController
   public class EmpController {
          
   
   @Autowired
   EmployeeMapper employeeMapper;
   
   @GetMapping("/emp/{id}")
   public Employee getEmp(@PathVariable("id")Integer id){
          
       return employeeMapper.getEmpById(id);
   	}
   
   }
   

5. 运行（记得现在employee表中先添加数据）
   

注解法和配置法的mybatis可以共存

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该SpringBoot学习笔记学习自雷神前辈，是对知识点的整理和自我认识的梳理，如有不当之处，欢迎指出