使用 @Cacheable java.lang.NullPointerException: null

@Cacheable java.lang.NullPointerException: null at java.lang.String.concat(String.java:2027)

异常信息

java.lang.NullPointerException: null
	at java.lang.String.concat(String.java:2027)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:497)
	at org.springframework.expression.spel.support.ReflectiveMethodExecutor.execute(ReflectiveMethodExecutor.java:117)
	at org.springframework.expression.spel.ast.MethodReference.getValueInternal(MethodReference.java:130)
	at org.springframework.expression.spel.ast.MethodReference.access$000(MethodReference.java:50)
	at org.springframework.expression.spel.ast.MethodReference$MethodValueRef.getValue(MethodReference.java:348)
	at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:88)
	at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:121)
	at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:262)
	at org.springframework.cache.interceptor.CacheOperationExpressionEvaluator.key(CacheOperationExpressionEvaluator.java:117)
	at org.springframework.cache.interceptor.CacheAspectSupport$CacheOperationContext.generateKey(CacheAspectSupport.java:741)
	at org.springframework.cache.interceptor.CacheAspectSupport.generateKey(CacheAspectSupport.java:557)
	at org.springframework.cache.interceptor.CacheAspectSupport.findCachedItem(CacheAspectSupport.java:501)
	at org.springframework.cache.interceptor.CacheAspectSupport.execute(CacheAspectSupport.java:388)
	at org.springframework.cache.interceptor.CacheAspectSupport.execute(CacheAspectSupport.java:326)
	at org.springframework.cache.interceptor.CacheInterceptor.invoke(CacheInterceptor.java:61)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673)
	at com.jfintech.jbs.biz.ProductBiz$$EnhancerBySpringCGLIB$$27398e56.findProductInfoWhiteList(<generated>)
	at com.jfintech.jbs.service.impl.ProductServiceImpl.getProductList(ProductServiceImpl.java:97)
	at com.jfintech.jbs.controller.ProductController.lambda$queryProductList$49(ProductController.java:58)
	at org.springframework.web.context.request.async.WebAsyncManager$5.run(WebAsyncManager.java:327)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)

错误代码示例：

 @Cacheable(cacheNames = "productInfos",cacheManager="jfinetchRedisCacheManager", key = "'jbs:product:white:'.concat(#reqest.getChannelCode()).concat(#p2)")
    public List<ProductInfoVO> findProductInfoWhiteList(CommonRequest<ReqProductVO> reqest,String productCodes){
        List<ProductInfoVO> redisList = productService.findList(reqest);
        redisList = redisList.stream().filter(it ->
                ProductStatusEnum.OPEN.getCode().equals(it.getStatus()) || (it.getStatus().equals(ProductStatusEnum.WHITE.getCode()) && productCodes.indexOf(it.getProductId().concat("]"))>=0)
        ).collect(Collectors.toList());

        return redisList;
    }

错误原因分析

1. 出现此问题应该是入参为空导致
   于是debug，发现reqest.getChannelCode()和productCodes都不为空，继续分析异常信息。
   
   看到这源码基本上能肯定是String concat的时候为空，这样看来应该是注解中的参数获取不正确。
2. 参数获取方式不正确
   继续回去检查代码发现第二参数写的#p2
   @ Cacheable（key = “‘key’+＃p0 +＃p1 +＃p2” ）一般用法，＃p0表示方法的第一个参数，＃p1表示第二个参数，以此类推。

解决方法

把#p2改成#p1，问题解决，正确代码如下。

    @Cacheable(cacheNames = "productInfos",cacheManager="jfinetchRedisCacheManager", key = "'jbs:product:white:'.concat(#reqest.getChannelCode()).concat(#p1)")
    public List<ProductInfoVO> findProductInfoWhiteList(CommonRequest<ReqProductVO> reqest,String productCodes){
        List<ProductInfoVO> redisList = productService.findList(reqest);
        redisList = redisList.stream().filter(it ->
                ProductStatusEnum.OPEN.getCode().equals(it.getStatus()) || (it.getStatus().equals(ProductStatusEnum.WHITE.getCode()) && productCodes.indexOf(it.getProductId().concat("]"))>=0)
        ).collect(Collectors.toList());

        return redisList;
    }