使用@Cached注解时，若设置模式为Remote并且cacheNullValue=true，Fastjson2Decoder会报NPE

[jxzhangaoran]

JetCache版本：2.7.3

@cached注解标注的方法如下：

    @Cached(name = "jet-cache-test:tryCacheNullValueRemote:", expire = 1,
            timeUnit = TimeUnit.MINUTES, cacheType = CacheType.REMOTE, cacheNullValue = true)
    public Object tryCacheNullValueRemote(boolean returnNullValue) {
        return returnNullValue ? null : System.currentTimeMillis();
    }

全局Spring配置

    @Bean
    public GlobalCacheConfig config(Pool<Jedis> pool) {
        Map localBuilders = new HashMap();
        EmbeddedCacheBuilder localBuilder = CaffeineCacheBuilder
                .createCaffeineCacheBuilder()
                .keyConvertor(Fastjson2KeyConvertor.INSTANCE);
        localBuilders.put(CacheConsts.DEFAULT_AREA, localBuilder);

        Map remoteBuilders = new HashMap();
        RedisCacheBuilder remoteCacheBuilder = RedisCacheBuilder.createRedisCacheBuilder()
                .keyConvertor(Fastjson2KeyConvertor.INSTANCE)
                // 这里使用了Fastjson2编解码
                .valueEncoder(Fastjson2ValueEncoder.INSTANCE)
                .valueDecoder(Fastjson2ValueDecoder.INSTANCE)
                .jedisPool(pool);
        remoteBuilders.put(CacheConsts.DEFAULT_AREA, remoteCacheBuilder);

        GlobalCacheConfig globalCacheConfig = new GlobalCacheConfig();
        globalCacheConfig.setLocalCacheBuilders(localBuilders);
        globalCacheConfig.setRemoteCacheBuilders(remoteBuilders);
        globalCacheConfig.setStatIntervalMinutes(1);

        return globalCacheConfig;
    }

当tryCacheNullValueRemote方法传入true时，报错日志如下：

2023-07-28 11:38:27,531 ERROR [com.alicp.jetcache.AbstractCache] - jetcache(RedisCache) GET error. key=[[true]]
com.alicp.jetcache.support.CacheEncodeException: decode error
	at com.alicp.jetcache.support.AbstractValueDecoder.apply(AbstractValueDecoder.java:48) ~[jetcache-core-2.7.3.jar:?]
	at com.alicp.jetcache.support.AbstractValueDecoder.apply(AbstractValueDecoder.java:11) ~[jetcache-core-2.7.3.jar:?]
	at com.alicp.jetcache.redis.RedisCache.do_GET(RedisCache.java:178) [jetcache-redis-2.7.3.jar:?]
	at com.alicp.jetcache.AbstractCache.GET(AbstractCache.java:83) [jetcache-core-2.7.3.jar:?]
	at com.alicp.jetcache.AbstractCache.computeIfAbsentImpl(AbstractCache.java:145) [jetcache-core-2.7.3.jar:?]
	at com.alicp.jetcache.AbstractCache.computeIfAbsent(AbstractCache.java:114) [jetcache-core-2.7.3.jar:?]
	at com.alicp.jetcache.Cache.computeIfAbsent(Cache.java:312) [jetcache-core-2.7.3.jar:?]
	at com.alicp.jetcache.anno.method.CacheHandler.invokeWithCached(CacheHandler.java:264) [jetcache-anno-2.7.3.jar:?]
	at com.alicp.jetcache.anno.method.CacheHandler.doInvoke(CacheHandler.java:107) [jetcache-anno-2.7.3.jar:?]
	at com.alicp.jetcache.anno.method.CacheHandler.invoke(CacheHandler.java:99) [jetcache-anno-2.7.3.jar:?]
	at com.alicp.jetcache.anno.aop.JetCacheInterceptor.invoke(JetCacheInterceptor.java:91) [jetcache-anno-2.7.3.jar:?]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) [spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749) [spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:691) [spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at matsk.middlewaretest.cache.JetCacheTestCache$$EnhancerBySpringCGLIB$$76b076b2.tryCacheNullValueRemote(<generated>) [classes/:?]
	at matsk.middlewaretest.controller.CacheTestController.testJetCacheWithNullValue(CacheTestController.java:38) [classes/:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_211]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_211]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_211]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_211]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) [spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) [spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) [spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879) [spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) [spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) [spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) [spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) [spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) [spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_211]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_211]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.36.jar:9.0.36]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_211]
Caused by: java.lang.NullPointerException: no decoder for identity number:-153049663
	at java.util.Objects.requireNonNull(Objects.java:228) ~[?:1.8.0_211]
	at com.alicp.jetcache.support.AbstractValueDecoder.apply(AbstractValueDecoder.java:42) ~[jetcache-core-2.7.3.jar:?]
	... 65 more

上述代码若将全局配置的编解码改成JavaValueEncoder/JavaValueDecoder时，则不会有这个报错。怀疑和Fastjson2ValueDecoder的实现有关。

[areyouok]

这是因为你的Fastjson2ValueDecoder没有注册，看看DecoderMap这个类你就知道了。

默认不注册json序列化器的原因是，json不是一个好的序列化方式，它的兼容性会有很多问题。如果我提供了，会有更多人遇到更多问题然后跑来问。