SpringBoot06-数据访问

简介

1. 对于数据访问层, 无论是SQL还是NOSQL, SpringBoot都默认采用Spring Data的方式处理.
2. SpringBoot会添加大量自动的配置, 屏蔽很多设置, 引入各种xxxTemplate, xxxRepository来简化我们对数据访问层的操作.
   • 注意是没有mybatis的starter的.

整合JDBC

1. 引入相关依赖

   <dependency>                                         
              <groupId>org.springframework.boot</groupId>      
              <artifactId>spring-boot-starter-jdbc</artifactId>
          </dependency>                                        
                                                               
          <dependency>                                         
              <groupId>mysql</groupId>                         
              <artifactId>mysql-connector-java</artifactId>    
              <scope>runtime</scope>                           
          </dependency>

2. 在application.yml中配置

   spring:
     datasource:
       username: root
       password: root
       url: jdbc:mysql://192.168.47.132:3407/jdbc
       driver-class-name: com.mysql.cj.jdbc.Driver
   
   #注意: com.mysql.jdbc.Driver已被弃用
   Loading class `com.mysql.jdbc.Driver‘. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver‘. 
   The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

3. 效果
   1. 默认是用com.zaxxer.hikari.HikariDataSource作为数据源.
   2. 数据源的配置文件都在DataSourceProperties中.

整合Druid数据源

1. 加入依赖

   <!-- 引入druid数据源 -->
   <dependency>
       <groupId>com.alibaba</groupId>
       <artifactId>druid</artifactId>
       <version>1.1.18</version>
   </dependency>

2. 配置文件中修改源类型

   spring.datasource.type: com.alibaba.druid.pool.DruidDataSource

3. 添加Druid的一些配置

   Spring:
     datasource: 
       ...
   
       initialSize: 5 #初始化数据库连接池大小
       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

4. 此时这些配置还未生效, 我们需要写配置类使其对应

   @Configuration
   public class DruidConfig {
   
       @ConfigurationProperties(prefix = "spring.datasource")
       @Bean
       public DataSource druid() {
           return new DruidDataSource();
       }
   }

5. 在配置类中配置一下Druid的监控

   //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", ""); //默认允许所有访问
           initParams.put("deny", "192.168.15.21");
           bean.setInitParameters(initParams);
           return bean;
       }
       //2.配置一个监控的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.setUrlPatterns(Arrays.asList("/*"));
           bean.setInitParameters(initParams);
           return bean;
       }

6. 之后就能查看后台监控了
   1. 

整合Mybatis

• 添加依赖, 配置Druid, 创建数据表, JavaBean
  1. 依赖信息

     <dependency>
         <groupId>org.mybatis.spring.boot</groupId>
         <artifactId>mybatis-spring-boot-starter</artifactId>
         <version>2.1.2</version>
     </dependency>

     • 这个不是springboot的starter, 而是mybatis为了适配springboot, 自己写的.
     • 
  2. JavaBean

     @NoArgsConstructor
     @AllArgsConstructor
     @Data
     public class Department {
     
         private Integer id;
         private String departmentName;
     }
     
     
     @NoArgsConstructor
     @AllArgsConstructor
     @Data
     public class Employee {
         private Integer id;
         private String lastName;
         private Integer gender;
         private String email;
         private Integer dId;
     }

•  注解版
  1. 创建Mapper接口, 加@Mapper注解, 指定这是一个操作数据库的mapper.

     @Component
     @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 delDeptById(Integer id);
     
         //如果插入的表id以自增列为主键, 则允许JDBC支持自动生成主键, 并可将自动生成的主键id返回.
         @Options(useGeneratedKeys = true, keyProperty = "id")
         @Insert("insert into department(departmentName) values(#{departmentName})")
         public int insertDept(Department dept);
     
         @Update("update department set departmentName=#{departmentName} where id=#{id}")
         public int updateDept(Department dept);
     }

  2. 如何自定义配置规则: 在配置类中给容器中添加一个ConfigurationCustomizer.

     @org.springframework.context.annotation.Configuration
     public class MybatisConfig {
     
         //自定义Mybatis的配置规则, 给容器中添加ConfigurationCustomizer组件
         @Bean
         public ConfigurationCustomizer configurationCustomizer() {
             return new ConfigurationCustomizer() {
     
                 @Override
                 public void customize(Configuration configuration) {
                     //开启驼峰命名法
                     configuration.setMapUnderscoreToCamelCase(true);
                 }
             };
         }
     }

  3. 若Mapper接口太多, 每个都加@Mapper麻烦, 可以在主启动类上加@MappperScan或@MapperScans

     //使用MapperScan批量扫描所有的Mapper接口
     @MapperScan(value = "top.binwenhome.springboot.mapper")
     @SpringBootApplication
     public class Springboot06MybatisApplication {
     
         public static void main(String[] args) {
             SpringApplication.run(Springboot06MybatisApplication.class, args);
         }
     }

• 配置文件版
  1. 要在application.yml/properties中指定

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

  2. 之后便是mybatis的常规操作了.
• 注解版和配置文件版是可以混合使用的.

SpringBoot06-数据访问

原文：https://www.cnblogs.com/binwenhome/p/12900702.html