SpringBoot @CachePut注解的使用原理

@CachePut

既调用方法，又更新缓存数据

在之前的分享的时候对于@Cacheable注解是在方法调用之前先去插叙缓存，但是CachePut注解是先调用方法，然后将方法的返回值放入到缓存中。

测试步骤

1.先进行员工数据的查找
2.进行员工数据的更新

第一次请求的时候由于缓存中没有数据，所以就进行查询数据库的操作并打印出对应的SQL。

第二次请求的时候由于数据已经存在于缓存中所以就不会进行数据库的查询操作。

当时当我们发送更新请求的时候报出了下面这样的错误

2019-04-06 15:05:39.584 ERROR 13016 --- [nio-8081-exec-6] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalStateException: No cache could be resolved for 'Builder[public com.example.cache.bean.Employee com.example.cache.service.EmployeeService.updateEmp(com.example.cache.bean.Employee)] caches=[] | key='' | keyGenerator='' | cacheManager='' | cacheResolver='' | condition='' | unless=''' using resolver 'org.springframework.cache.interceptor.SimpleCacheResolver@69517dad'. At least one cache should be provided per cache operation.] with root cause

java.lang.IllegalStateException: No cache could be resolved for 'Builder[public com.example.cache.bean.Employee com.example.cache.service.EmployeeService.updateEmp(com.example.cache.bean.Employee)] caches=[] | key='' | keyGenerator='' | cacheManager='' | cacheResolver='' | condition='' | unless=''' using resolver 'org.springframework.cache.interceptor.SimpleCacheResolver@69517dad'. At least one cache should be provided per cache operation.
	at org.springframework.cache.interceptor.CacheAspectSupport.getCaches(CacheAspectSupport.java:242) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.cache.interceptor.CacheAspectSupport$CacheOperationContext.<init>(CacheAspectSupport.java:672) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.cache.interceptor.CacheAspectSupport.getOperationContext(CacheAspectSupport.java:252) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.cache.interceptor.CacheAspectSupport$CacheOperationContexts.<init>(CacheAspectSupport.java:578) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.cache.interceptor.CacheAspectSupport.execute(CacheAspectSupport.java:324) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.cache.interceptor.CacheInterceptor.invoke(CacheInterceptor.java:61) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673) ~[spring-aop-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at com.example.cache.service.EmployeeService$$EnhancerBySpringCGLIB$$32780528.updateEmp(<generated>) ~[classes/:na]
	at com.example.cache.controller.EmployeeController.update(EmployeeController.java:23) ~[classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_144]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_144]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_144]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_144]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97) ~[spring-webmvc-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[spring-webmvc-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[spring-webmvc-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967) ~[spring-webmvc-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) ~[spring-webmvc-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[spring-webmvc-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[spring-webmvc-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.16.RELEASE.jar:4.3.16.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_144]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_144]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.29.jar:8.5.29]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_144]

而这个问题的错误的原因在于，我们之前说过了CachePut注解在使用的时候是先进行数据库的查库操作，然后在更新缓存，由于要更新缓存，所以一定要指定所要操作的缓存的名称
在注解上加入对应的缓存名称然后进行对应的更新操作。

  @CachePut(value = "emp")

解决完上面的问题之后现在来模拟一个新的场景

1.查询1号员工，查到结果会放在缓存中
key：1 value ：lastName nihui
2.但是第二次查询之后还是之前的结果
3.更新1号员工
传入的参数是员工，返回的信息的也是一个员工

操作步骤

更新缓存操作

再次查询1号员工发现还是原来的数据


但是实际上并没有进行数据库的查询，也就是说在更新的时候并没有更新缓存。

为什么没有更新缓存

因为CachePut是方法运行完成之后然后再往缓存中放入数据，所以使用以下的方式进行操作

@CachePut(value = "emp0",key = "#employee.id")

这个是以方法的参数ID进行缓存操作,当然还可以使用下面这种方式进行操作。拿出返回值的id。在这里需要注意的一点是Cacheable的key是不能用#result取出对应的返回值的。

@CachePut(value = "emp0",key = "#result.id")

当执行完这些操作之后就可以保证在更新完成数据之后缓存中的指定的数据也会发生变化。这样的话就完成同步更新缓存的目的。