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lazyczx
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[Spring-boot] 学 CommandLineRunner 的时候发生的一件神奇的事情,这怎么解释?

  •  1
     
  •   lazyczx · 2021-12-22 15:54:58 +08:00 · 523 次点击
    这是一个创建于 1052 天前的主题,其中的信息可能已经有所发展或是发生改变。

    kaze 15:39:00 大哥你知不知道 CommandLineRunner 运行时的环境和 Controller 监听 request 运行的环境有啥区别

    kaze 15:39:24

    @Bean
    	public CommandLineRunner run(RestTemplate restTemplate){
    		return args -> {
    			Thread t = new Thread(()-> {
    				try {
    					TimeUnit.SECONDS.sleep(3);
    				} catch (InterruptedException e) {
    					e.printStackTrace();
    				}
    				Greeting greeting = restTemplate.getForObject(
    						"http://localhost:8080/greeting",
    						Greeting.class
    				);
    				assert greeting != null;
    				log.info(greeting.toString());
    			});
    
    			t.start();
    			t.join();
    			log.info("done");
    		};
    	}
    

    kaze 15:39:28

    @GetMapping("/get_greeting")
        public Greeting getGreeting(@RequestParam(value = "name", defaultValue = "World") String name,
                                    RestTemplate restTemplate) {
            Greeting g = restTemplate.getForObject(
                    "http://localhost:8080/greeting",
                    Greeting.class
            );
            assert g != null;
            log.info(g.toString());
            return g;
        }
    

    kaze 15:40:11 CommandLineRunner 不是会容器开启的时候自动运行吗,然后我在里面用 RestTemplate get 了自己这个容器开的一个 Api 能正常运行的

    kaze 15:40:19

    2021-12-22 15:42:19.857  INFO 21948 --- [       Thread-6] c.e.restservice.RestServiceApplication   : Greeting{id=1, content='Hello, World!'}
    2021-12-22 15:42:19.857  INFO 21948 --- [           main] c.e.restservice.RestServiceApplication   : done
    
    2021-12-22 15:52:22.801 ERROR 21948 --- [nio-8080-exec-3] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.http.converter.HttpMessageConversionException: Type definition error: [simple type, class com.example.restservice.Greeting]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `com.example.restservice.Greeting` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
     at [Source: (PushbackInputStream); line: 1, column: 2]] with root cause
    
    com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `com.example.restservice.Greeting` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
     at [Source: (PushbackInputStream); line: 1, column: 2]
    	at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:67) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at com.fasterxml.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1764) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:400) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1209) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1415) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:362) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:195) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4593) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3601) ~[jackson-databind-2.12.3.jar:2.12.3]
    	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:378) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:342) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:105) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:778) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:711) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:334) ~[spring-web-5.3.8.jar:5.3.8]
    	at com.example.restservice.GreetingController.getGreeting(GreetingController.java:31) ~[classes/:na]
    	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_291]
    	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_291]
    	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_291]
    	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_291]
    	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.8.jar:5.3.8]
    	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.8.jar:5.3.8]
    	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.8.jar:5.3.8]
    	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.8.jar:5.3.8]
    	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1063) ~[spring-webmvc-5.3.8.jar:5.3.8]
    	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:963) ~[spring-webmvc-5.3.8.jar:5.3.8]
    	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.8.jar:5.3.8]
    	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.8.jar:5.3.8]
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:655) ~[tomcat-embed-core-9.0.48.jar:4.0.FR]
    	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.8.jar:5.3.8]
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:764) ~[tomcat-embed-core-9.0.48.jar:4.0.FR]
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:228) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.8.jar:5.3.8]
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1723) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_291]
    	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_291]
    	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.48.jar:9.0.48]
    	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_291]
    
    

    kaze 15:40:35 然后我在 GetMapping 里,一样的代码就失败了

    kaze 15:41:50 我 debug 了一下,发现 com.fasterxml.jackson.databind.deser.BeanDeserializerBase 这个类里的方法 deserializeFromObjectUsingNonDefault

    kaze 15:42:23 在 CommandLineRunner 下运行的时候,这个_propertyBasedCreator 就不为 null

    kaze 15:42:44 在 Controller 里运行,这里这个属性就是 null

    kaze 15:42:46 这是为啥

    lazyczx
        1
    lazyczx  
    OP
       2021-12-22 15:55:36 +08:00
    ddddddddddddddd
    1194129822
        2
    1194129822  
       2021-12-22 19:17:20 +08:00
    是在同一个项目里吗?打断点看一下注入的是否是同一个 restTemplate 。restTemplate 的属性是否一致。jackson 保错,Greeting 没有默认构造器。
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