SpringBoot Cache 入门

1. 首先搭载开发环境，不会的可以参考笔者之前的文章SpringBoot入门

   添加依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
   </dependency>
  

1. 开始配置Cache

   a. 在启动类增加一个注解@EnableCaching

@SpringBootApplication
   @MapperScan("com.tanoak.mapper")
   @EnableCaching
   public class BootCacheApplication {
   ​
    public static void main(String[] args) {
    SpringApplication.run(BootCacheApplication.class, args);
    }
   } 

b.  pojo

@Data
    public class Teacher {//使用Lombok注解

     private Integer id;
     private String lastName;
     private String email;
    ​
     /**
     *性别 1男  0女
     */
     private Integer sex;
     private Integer sId;
    } 

c. Mapper

 @Mapper
    public interface TeacherMapper {
    ​
     @Select("SELECT * FROM teacher WHERE id =#{id}")
     Teacher getTeaById(Integer id);
    ​
     @Update("UPDATE teacher SET lastName =#{lastName},email=#{email},sex=#{sex},s_id=#{sId} WHERE id=#{id}")
     Integer update(Teacher teacher) ;
    ​
     @Delete("DELETE FROM teacher WHERE id =#{id}")
     Integer deleteById(Integer id) ;
    ​
     @Insert("INSERT INTO teacher(lastName,email,sex,t_id) VALUES(#{lastName},#{email},#{sex},#{sId})")
     Integer insert(Teacher teacher) ;
    }

d. Service

public interface TeacherService {
   ​
    /**
    *  根据ID查询实体
    * @param id
    * @return
    */
   ​
    Teacher getEmpById(Integer id) ;

    Integer update(Teacher teacher) ;
    Integer remove(Integer id) ;
   }
   ​
   //实现类
   ​
   @Service
   public class TeacherServiceImpl implements TeacherService {
   ​
    private static final Logger logger = LoggerFactory.getLogger(TeacherServiceImpl.class);
   ​
    @Resource
    private TeacherMapper teacherMapper ;
   ​
    @Override
    @Cacheable(cacheNames = {"emp"},condition = "#id>0")
    public Teacher getEmpById(Integer id) {
    logger.info("进行查询实体 ID为"+id);
    return teacherMapper.getTeaById(id) ;
    }
   ​
    @Override
    public Integer update(Teacher teacher) {
    logger.info("修改的实体为"+teacher.toString());
    return teacherMapper.update(teacher) ;
    }
   ​
    @Override
    public Integer remove(Integer id) {
    logger.info("删除的实体 ID为"+id);
    return teacherMapper.deleteById(id) ;
    }
   }

e. Controller

@RestController
 public class TeacherController {
 ​
  @Resource
  private TeacherService teacherService ;
 ​
  @GetMapping("/tea/{id}")
  @Cacheable(cacheNames = "tea")
  public Teacher getTea(@PathVariable("id")Integer id){
  return  teacherService.getEmpById(id) ;
  }
 }

然后就开启缓存，本篇文章结束！开个玩笑，在正常的开发中，我们的CRUD需要进行缓存的环节一般是在查询，更新，删除，在一些特殊的业务场景下也会对插入进行缓存，这里不做考虑。然后我们根据需求想要解决这个问题，那么Cache对应的注解就出现了

#根据方法的请求参数对其结果进行缓存
    @Cacheable
    -----------
    #保证方法被调用，又希望结果被缓存。
    @CachePut
    ------------
    清空缓存
    @CacheEvict

了解这三个注解我们来看下如何使用吧

@Cacheable

这个注解有多个属性

key  缓存的 key 支持SpEl表达式

keyGenerator  自定义Key生成策略  二选一（key or keyGenerator）
​
condition   符合指定条件缓存
​
unless 条件为true不缓存 

@Override
 @Cacheable(cacheNames = "tea",key = "#id",condition = "#id>1")
 public Teacher getTeaById(Integer id) {
 logger.info("进行查询实体 ID为"+id);
 return teacherMapper.getTeaById(id) ;
}
​
@GetMapping("/tea/{id}")
 public Teacher getTea(@PathVariable("id")Integer id){
 return  teacherService.getEmpById(id) ;
 }

自定义KeyGenerator

public class MyKeyGenerator {
​
 @Bean("mykeyGenerator")
 public KeyGenerator keyGenerator(){
 return new KeyGenerator(){
 @Override
 public Object generate(Object target, Method method, Object ...params){
 return method.getName() +"{"+Arrays.asList(params) +"}";
 }
 };
 }
}

​

 @Cacheable(cacheNames = "tea",keyGenerator="mykeyGenerator")
 public Teacher getTeaById(Integer id) {
 logger.info("进行查询实体 ID为"+id);
 return teacherMapper.getTeaById(id) ;
 }

​
@GetMapping("/tea2/{id}")
 public Teacher getTea2(@PathVariable("id")Integer id){
 return  teacherService.getTeaById(id) ;
 }```

目前解决了查询的缓存，接下来处理更新的缓存

## @CachePut

这个注解是在方法执行完成后调用的与@Cacheable的调用顺序刚好相反

@GetMapping("/tea")
@CachePut(cacheNames = "tea")
public Teacher upTea(Teacher teacher){
teacherService.update(teacher) ;
return teacher ;
}```

可以看到，再次点击查询的时候没有发送sql语句，说明已经缓存成功

@CacheEvict

清空缓存，来认识一下

@Override @CacheEvict(cacheNames = "tea",key = "#id") public Integer remove(Integer id) { logger.info("删除的实体 ID为"+id); // return teacherMapper.deleteById(id) ; return 1 ; } //然后再Controller中调用 @GetMapping("/tea3/{id}") public String delTea(@PathVariable("id")Integer id){ teacherService.remove(id) ; System.out.println("测试删除缓存 id为"+id); return "OK" ; }

Cache的基本用法到这里就结束了，下片文章我们深入探讨它的运行机制。如理解有误，请指正