The operator 'ADD' is not supported between objects of type 'java.lang.Long' and 'null'

Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1030E: The operator 'ADD' is not supported between objects of type 'java.lang.Long' and 'null'
	at org.springframework.expression.spel.ExpressionState.operate(ExpressionState.java:223) ~[spring-expression-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.expression.spel.ast.OpPlus.getValueInternal(OpPlus.java:139) ~[spring-expression-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:121) ~[spring-expression-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:262) ~[spring-expression-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.cache.interceptor.CacheOperationExpressionEvaluator.key(CacheOperationExpressionEvaluator.java:117) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.cache.interceptor.CacheAspectSupport$CacheOperationContext.generateKey(CacheAspectSupport.java:739) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.cache.interceptor.CacheAspectSupport.generateKey(CacheAspectSupport.java:555) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.cache.interceptor.CacheAspectSupport.findCachedItem(CacheAspectSupport.java:499) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.cache.interceptor.CacheAspectSupport.execute(CacheAspectSupport.java:386) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.cache.interceptor.CacheAspectSupport.execute(CacheAspectSupport.java:324) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.cache.interceptor.CacheInterceptor.invoke(CacheInterceptor.java:61) ~[spring-context-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:671) ~[spring-aop-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_102]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_102]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_102]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_102]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133) ~[spring-web-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97) ~[spring-webmvc-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[spring-webmvc-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[spring-webmvc-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967) ~[spring-webmvc-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) ~[spring-webmvc-4.3.18.RELEASE.jar:4.3.18.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.18.RELEASE.jar:4.3.18.RELEASE]

在使用 spring 缓存注解 Cacheable 设置 key 时，取了方法中的一个参数，但这个参数类型为 Long，显然，这个表达式不支持 Long 类型，方法就是转换为 String，如

 @Cacheable(value = "kylin_config_3", key = "T(String).valueOf(#longPar) + #p2 + #p3")