Could not extract response: no suitable HttpMessageConverter

我不是女神ヾ 2024-03-26 14:29 80阅读 0赞

版本：spring-cloud-openfeign-core-2.1.1.RELEASE.jar，spring-webmvc-5.1.14.RELEASE.jar，jetty-server-9.4.41.v20210516.jar，tomcat-embed-core-9.0.48.jar

### 问题背景 ###

生产服务请求下游服务时偶发抛出下面的异常，下游服务已经很久没有人发布并且没有修改任何配置，而且是偶发，这个问题很奇怪，服务使用的Spring cloud openfeign，由于不熟悉Spring cloud与openfeign，先梳理学习Spring cloud openfeign bean的初始化与定义

feign.codec.DecodeException: Could not extract response: no suitable HttpMessageConverter found for response type [class com.....master.models.APIResponse] and content type [application/xhtml+xml;charset=UTF-8]
        at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:180)
        at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:140)
        at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:78)
        at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103)
        at com.sun.proxy.$Proxy401.sendEmail(Unknown Source)
        at ......
        Caused by: org.springframework.web.client.RestClientException: Could not extract response: no suitable HttpMessageConverter found for response type [class com.......APIResponse] and content type [application/xhtml+xml;charset=UTF-8]
        at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:121)
        at org.springframework.cloud.openfeign.support.SpringDecoder.decode(SpringDecoder.java:59)
        at org.springframework.cloud.openfeign.support.ResponseEntityDecoder.decode(ResponseEntityDecoder.java:62)
        at feign.optionals.OptionalDecoder.decode(OptionalDecoder.java:36)
        at feign.SynchronousMethodHandler.decode(SynchronousMethodHandler.java:176)
        ... 106 more

### Spring Cloud openfeign ###

#### 初始化过程 ####

应用启动SpringBootApplication，引入自动配置sdk，自动配置：org.springframework.cloud.openfeign.FeignAutoConfiguration

##### FeignAutoConfiguration #####

1.  构建feignContext：org.springframework.cloud.openfeign.FeignContext，FeignContext是Spring应用上下文与feignClient配置org.springframework.cloud.openfeign.FeignClientSpecification的组合
2.  按需（@ConditionalOnClass(name = “feign.hystrix.HystrixFeign”)）构建feignTargeter：HystrixTargeter，默认（@ConditionalOnMissingClass(“feign.hystrix.HystrixFeign”)）：DefaultTargeter
3.  按需构建HttpClientFeignConfiguration，条件见：下方代码
4.  按需构建OkHttpFeignConfiguration，条件见：下方代码

@ConditionalOnClass(ApacheHttpClient.class)
    	@ConditionalOnMissingClass("com.netflix.loadbalancer.ILoadBalancer")
    	@ConditionalOnMissingBean(CloseableHttpClient.class)
    	@ConditionalOnProperty(value = "feign.httpclient.enabled", matchIfMissing = true)
    	protected static class HttpClientFeignConfiguration {
        
            ...
        }
    	@Configuration
    	@ConditionalOnClass(OkHttpClient.class)
    	@ConditionalOnMissingClass("com.netflix.loadbalancer.ILoadBalancer")
    	@ConditionalOnMissingBean(okhttp3.OkHttpClient.class)
    	@ConditionalOnProperty("feign.okhttp.enabled")
    	protected static class OkHttpFeignConfiguration {
        
            ...
        }

查看注解：@EnableFeignClients(basePackages = \{“…”\}),客户端注入过程切入点，该注解会通过Spring Import注解导入bean定义，注解指定导入bean定义类：org.springframework.cloud.openfeign.FeignClientsRegistrar

##### 注册BeanDefinitions流程 #####

1.  registerDefaultConfiguration
2.  registerFeignClients

##### registerDefaultConfiguration #####

1.  获取EnableFeignClients注解默认属性配置
2.  如果默认配置包含（defaultConfiguration），则将默认配置注册为bean（FeignClientSpecification）。beanName：default…notification.Application

##### registerFeignClients #####

1.  使用ClassPathScanningCandidateComponentProvider扫描器按照EnableFeignClients配置的basePackages扫描当前资源resourceLoader，扫描过滤器AnnotationTypeFilter筛选出FeignClient注解的AnnotatedBeanDefinition
2.  根据FeignClient注解的属性（configuration）定义构建FeignClientSpecification的BeanDefinition，注册客户端配置方法代码如下

private void registerClientConfiguration(BeanDefinitionRegistry registry, Object name,
    			Object configuration) {
        
    		BeanDefinitionBuilder builder = BeanDefinitionBuilder
    				.genericBeanDefinition(FeignClientSpecification.class);
    		builder.addConstructorArgValue(name);
    		builder.addConstructorArgValue(configuration);
    		registry.registerBeanDefinition(
    				name + "." + FeignClientSpecification.class.getSimpleName(),
    				builder.getBeanDefinition());
    	}

##### registerFeignClient #####

1.  构建客户端bean：FeignClientFactoryBean
2.  将bean封装为：BeanDefinitionHolder注册至工厂
    
    1.  bean名称为className
    2.  feign client bean别名使用注解属性（FeignClient）：qualifier，兜底使用：contextId+FeignClient，contextId读取注解属性优先级：contextId>name，name注解属性优先级：serviceId>name>value

代码如下

private void registerFeignClient(BeanDefinitionRegistry registry,
    			AnnotationMetadata annotationMetadata, Map<String, Object> attributes) {
        
    		String className = annotationMetadata.getClassName();
    		BeanDefinitionBuilder definition = BeanDefinitionBuilder
    				.genericBeanDefinition(FeignClientFactoryBean.class);
    		validate(attributes);
    		definition.addPropertyValue("url", getUrl(attributes));
    		definition.addPropertyValue("path", getPath(attributes));
    		String name = getName(attributes);
    		definition.addPropertyValue("name", name);
    		String contextId = getContextId(attributes);
    		definition.addPropertyValue("contextId", contextId);
    		definition.addPropertyValue("type", className);
    		definition.addPropertyValue("decode404", attributes.get("decode404"));
    		definition.addPropertyValue("fallback", attributes.get("fallback"));
    		definition.addPropertyValue("fallbackFactory", attributes.get("fallbackFactory"));
    		definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
    		String alias = contextId + "FeignClient";
    		AbstractBeanDefinition beanDefinition = definition.getBeanDefinition();
    		boolean primary = (Boolean) attributes.get("primary"); // has a default, won't be
    																// null
    		beanDefinition.setPrimary(primary);
    		String qualifier = getQualifier(attributes);
    		if (StringUtils.hasText(qualifier)) {
        
    			alias = qualifier;
    		}
    		BeanDefinitionHolder holder = new BeanDefinitionHolder(beanDefinition, className,
    				new String[] {
         alias });
    		BeanDefinitionReaderUtils.registerBeanDefinition(holder, registry);
    	}

##### FeignClientFactoryBean #####

1.  获取FeignClient bean：org.springframework.cloud.openfeign.FeignClientFactoryBean\#getObject
2.  应用上下文中获取FeignContext
3.  创建Feign.Builder：org.springframework.cloud.openfeign.FeignClientFactoryBean\#feign
    
    1.  从FeignContext上下文获取构造者feign.Feign.Builder
    2.  为构建者设置encoder，从FeignContext上下文获取feign.codec.Encoder：org.springframework.cloud.openfeign.support.PageableSpringEncoder->SpringEncoder->SpringFormEncoder->feign.codec.Encoder.Default
    3.  为构建者设置decoder，从FeignContext上下文获取feign.codec.Decoder：feign.optionals.OptionalDecoder->org.springframework.cloud.openfeign.support.ResponseEntityDecoder->SpringDecoder
    4.  为构建者设置contract，从FeignContext上下文获取feign.Contract：使用feign.hystrix.HystrixDelegatingContract\#HystrixDelegatingContract代理包装自定义实现OpenFeignSpringMvcContract（继承自feign.OpenFeignBaseContract）
    5.  配置feign（configureFeign）：如果存在FeignClientProperties配置，则按照配置设置：loggerLevel/connectTimeout/readTimeout/Retryer/ErrorDecoder/RequestInterceptor/decode404/encoder/decoder/contract。注意配置优先级，如果spring上下文中存在配置bean，则：如果当前配置是默认配置，则当前配置<default配置<contextId对应的配置。否则：default配置<contextId对应的配置<当前配置。如果spring上下文中不存在配置bean，则仅按照当前配置设置feign
4.  如果不存在url配置：org.springframework.cloud.openfeign.FeignClientFactoryBean\#loadBalance
5.  否则
    
    1.  获取Client：org.springframework.cloud.openfeign.FeignClientFactoryBean\#getOptional。如果client不为空并且是LoadBalancerFeignClient类型则获取其代理的实际Client
    2.  获取Targeter：org.springframework.cloud.openfeign.FeignClientFactoryBean\#get
    3.  构建目标bean：org.springframework.cloud.openfeign.Targeter\#target（feign.Target.HardCodedTarget）

当前案例默认无url，即步骤3：org.springframework.cloud.openfeign.FeignClientFactoryBean\#loadBalance

1.  获取Client：org.springframework.cloud.openfeign.FeignClientFactoryBean\#getOptional。常用实现：ApacheHttpClient，OkHttpClient，feign.Client.Default。AnnotationConfigApplicationContext上下文（每一个应用都有一个独立的上下文，拥有同一个parent Spring应用上下文）仅管理FeignClient注解的bean。从中获取对应的bean（org.springframework.cloud.context.named.NamedContextFactory\#getInstance(java.lang.String, java.lang.Class)）。当前案例使用自定义封装ReWriteHeaderFeignClient客户端，继承自：org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient
2.  获取Targeter：org.springframework.cloud.openfeign.HystrixTargeter
3.  构建目标bean：org.springframework.cloud.openfeign.Targeter\#target（feign.Target.HardCodedTarget）

##### Client #####

配置入口：org.springframework.cloud.openfeign.ribbon.FeignRibbonClientAutoConfiguration-》org.springframework.cloud.openfeign.ribbon.HttpClientFeignLoadBalancedConfiguration\#feignClient  
默认实现：org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient\#LoadBalancerFeignClient

1.  lbClientFactory：配置入口org.springframework.cloud.openfeign.ribbon.FeignRibbonClientAutoConfiguration\#cachingLBClientFactory
2.  clientFactory：配置入口org.springframework.cloud.netflix.ribbon.RibbonAutoConfiguration\#springClientFactory

##### 构建目标bean #####

构建Feign：feign.hystrix.HystrixFeign.Builder\#build(feign.hystrix.FallbackFactory<?>)

1.  实现InvocationHandler：feign.hystrix.HystrixInvocationHandler
2.  包装contract：feign.hystrix.HystrixDelegatingContract\#HystrixDelegatingContract
3.  调用父类build方法构建Feign：feign.Feign.Builder\#build

public Feign build() {
        
      SynchronousMethodHandler.Factory synchronousMethodHandlerFactory =
          new SynchronousMethodHandler.Factory(client, retryer, requestInterceptors, logger,
              logLevel, decode404, closeAfterDecode, propagationPolicy);
      ParseHandlersByName handlersByName =
          new ParseHandlersByName(contract, options, encoder, decoder, queryMapEncoder,
              errorDecoder, synchronousMethodHandlerFactory);
      return new ReflectiveFeign(handlersByName, invocationHandlerFactory, queryMapEncoder);
    }

SynchronousMethodHandler.Factory工厂相关属性

1.  client:常用实现：ApacheHttpClient，OkHttpClient，feign.Client.Default。当前案例使用自定义封装ReWriteHeaderFeignClient客户端
2.  retryer:feign.Retryer.Default\#Default()
3.  requestInterceptors
    
    1.  自定义：OpenFeignRequestInterceptor
    2.  自定义：GrayPatternMatcherRequestInterceptor
    3.  自定义：GzipFeignAcceptGzipEncodingInterceptor继承FeignAcceptGzipEncodingInterceptor，如果配置feign.compression.response.enabled=true，则启用该拦截器，追加header Accept-Encoding -> gzip
    4.  自定义：FeignEnvFlagInterceptor
4.  decode404：false
5.  closeAfterDecode：true
6.  propagationPolicy：feign.Feign.Builder\#propagationPolicy（NONE）

ParseHandlersByName相关属性

1.  options：feign.Request.Options\#Options()，connectTimeoutMillis默认10s，readTimeoutMillis默认60s
2.  encoder，decoder，contract：同Feign.Builder
3.  queryMapEncoder：feign.QueryMapEncoder.Default
4.  errorDecoder：自定义实现new ErrorDecoder()
5.  contract：HystrixDelegatingContract

ReflectiveFeign相关属性

1.  invocationHandlerFactory：feign.InvocationHandlerFactory.Default。当前案例为内部实现类，工厂创建的handler为：HystrixInvocationHandler
2.  queryMapEncoder：同上
3.  handlersByName：ParseHandlersByName

创建目标实例  
feign.ReflectiveFeign\#newInstance

1.  获取nameToHandler映射：feign.ReflectiveFeign.ParseHandlersByName\#apply
    
    1.  解析与校验元数据：feign.Contract\#parseAndValidatateMetadata，当前案例：自定义实现重写父类方法feign.OpenFeignBaseContract\#parseAndValidateMetadata
    2.  processAnnotationOnClass
    3.  processAnnotationOnMethod
    4.  processAnnotationsOnParameter
    5.  checkState
    6.  checkMapString：HeaderMap
    7.  checkMapKeys：QueryMap
    8.  回调handler：feign.FeignClientMethodMetadataParseHandler\#parsed
2.  根据default与nameToHandler获取methodToHandler映射
3.  创建InvocationHandler：feign.InvocationHandlerFactory.Default\#create
4.  创建目标实例代理：java.lang.reflect.Proxy\#newProxyInstance(java.lang.ClassLoader, java.lang.Class<?>\[\], java.lang.reflect.InvocationHandler)
5.  如果是default方法：feign.Util\#isDefault，绑定feign.DefaultMethodHandler至动态代理
6.  返回代理对象

isDefault默认方法定义

// Default methods are public non-abstract, non-synthetic, and non-static instance methods
        // declared in an interface.
        // method.isDefault() is not sufficient for our usage as it does not check
        // for synthetic methods. As a result, it picks up overridden methods as well as actual default
        // methods.

动态代理InvocationHandler

static final class Default implements InvocationHandlerFactory {
        
    
        @Override
        public InvocationHandler create(Target target, Map<Method, MethodHandler> dispatch) {
        
          return new ReflectiveFeign.FeignInvocationHandler(target, dispatch);
        }
      }

#### 请求过程 ####

##### 关键对象属性 #####

FeignInvocationHandler

1.  target：HardCodedTarget
    
    1.  type：目标对象class，例如：MyTestAPI
    2.  name：my-feign-client
    3.  url：http://my-feign-client
2.  dispatch：key代理对象方法，例如：MyTestAPI.helloWorld()，value：feign.SynchronousMethodHandler

SynchronousMethodHandler

1.  与SynchronousMethodHandler.Factory相同部分不再重复，搜索上方关键字：SynchronousMethodHandler.Factory
2.  target：HardCodedTarget
3.  decoder，options，errorDecoder：同ParseHandlersByName.decoder
4.  metadata：feign.MethodMetadata
5.  buildTemplateFromArgs：feign.ReflectiveFeign.BuildEncodedTemplateFromArgs\#BuildEncodedTemplateFromArgs/BuildTemplateByResolvingArgs/BuildFormEncodedTemplateFromArgs
6.  client: 同工厂（SynchronousMethodHandler.Factory），当前案例为自定义实现：ReWriteHeaderFeignClient

FeignLoadBalancer

1.  lb:ZoneAwareLoadBalancer->com.netflix.loadbalancer.DynamicServerListLoadBalancer，定期更新server列表updateListOfServers
2.  config：com.netflix.client.config.DefaultClientConfigImpl

ZoneAwareLoadBalancer

1.  serverListImpl：org.springframework.cloud.netflix.ribbon.eureka.DomainExtractingServerList

DynamicServerListLoadBalancer

1.  list：com.netflix.niws.loadbalancer.DiscoveryEnabledNIWSServerList

DiscoveryEnabledNIWSServerList

1.  eurekaClientProvider:com.netflix.niws.loadbalancer.LegacyEurekaClientProvider，get获取返回EurekaClient：com.netflix.discovery.DiscoveryManager\#getDiscoveryClient/getEurekaClient
2.  obtainServersViaDiscovery：刷新服务实例列表方法，按照服务名称（vipAddresses，例如：MyEurekaService1,MyEurekaService2）获取实例列表：com.netflix.discovery.EurekaClient\#getInstancesByVipAddress(java.lang.String, boolean, java.lang.String)->com.netflix.discovery.DiscoveryClient\#getInstancesByVipAddress(java.lang.String, boolean, java.lang.String)

##### 请求过程 #####

1.  动态代理调用：feign.ReflectiveFeign.FeignInvocationHandler\#invoke
2.  调用代理方法：feign.SynchronousMethodHandler\#invoke
3.  创建RequestTemplate：feign.ReflectiveFeign.BuildTemplateByResolvingArgs\#create
    
    1.  解析参数构建EncodedTemplate对象：feign.ReflectiveFeign.BuildEncodedTemplateFromArgs\#resolve
    2.  encode request body：org.springframework.cloud.openfeign.support.PageableSpringEncoder\#encode->org.springframework.cloud.openfeign.support.SpringEncoder\#encode
    3.  org.springframework.http.converter.json.MappingJackson2HttpMessageConverter->org.springframework.http.converter.AbstractHttpMessageConverter\#write将request body写入org.springframework.cloud.openfeign.support.SpringEncoder.FeignOutputMessage
    4.  如果请求没有Content-Type header默认值设置为：application/json;charset=UTF-8
    5.  写入encoded body，并追加Content-Length header
4.  克隆Retryer：feign.Retryer.Default\#clone
5.  发起请求并解析响应结果：feign.SynchronousMethodHandler\#executeAndDecode
6.  构建请求：feign.SynchronousMethodHandler\#targetRequest
    
    1.  回调拦截器处理请求：feign.RequestInterceptor
    2.  创建request请求：feign.Target.HardCodedTarget\#apply-》feign.RequestTemplate\#request
7.  客户端执行请求：feign.SynchronousMethodHandler\#client\#execute(request, options)：org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient\#execute
8.  按照客户端名称创建负载均衡客户端：org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient\#lbClient-》org.springframework.cloud.openfeign.ribbon.CachingSpringLoadBalancerFactory\#create，从Spring client Factory中获取ILoadBalancer+IClientConfig，构建FeignLoadBalancer或RetryableFeignLoadBalancer
9.  负载均衡，构建LB命令：com.netflix.client.AbstractLoadBalancerAwareClient\#buildLoadBalancerCommand，如果LoadBalancerCommand.server为null则选择server：com.netflix.loadbalancer.reactive.LoadBalancerCommand\#selectServer-》com.netflix.loadbalancer.LoadBalancerContext\#getServerFromLoadBalancer-》com.netflix.loadbalancer.ZoneAwareLoadBalancer\#chooseServer-》自定义实现LB规则…platform.ribbon.wrapper.ZoneAvoidanceAndGrayAndLoadBasedRule\#choose（请求eureka刷新服务器列表com.netflix.discovery.DiscoveryClient\#refreshRegistry，按照LB规则选择服务器）
10. 提交命令执行请求。自定义实现com.netflix.loadbalancer.reactive.ServerOperation：重构Server请求URI：com.netflix.client.AbstractLoadBalancerAwareClient\#executeWithLoadBalancer(S, com.netflix.client.config.IClientConfig)-》com.netflix.loadbalancer.LoadBalancerContext\#reconstructURIWithServer
11. 完成请求返回响应结果feign.Response
12. decode response
13. org.springframework.web.client.HttpMessageConverterExtractor.extractData
14. 如果转换器类型为GenericHttpMessageConverter，根据responseType+contentType获取转换器GenericHttpMessageConverter
15. 否则根据responseClass+contentType获取转换器
16. HttpMessageConverter将response转换为目标方法返回值类型

### 问题分析 ###

#### 客户端 ####

ReWriteHeaderFeignClient自定义封装调用链路

1.  feign.SynchronousMethodHandler\#invoke->executeAndDecode->自定义实现ReWriteHeaderFeignClient\#execute ->org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient\#execute->org.springframework.cloud.openfeign.ribbon.LoadBalancerFeignClient\#lbClient->自定义实现EncodeHeaderCachingSpringLoadBalancerFactory\#create->FeignLoadBalancer(如果存在重试工厂loadBalancedRetryFactory则使用RetryableFeignLoadBalancer）->自定义实现EncodeHeaderCachingSpringLoadBalancerFactory.EncodeFeignLoadBalancer\#executeWithLoadBalancer->LoadBalancerCommand.submit->异步调用org.springframework.cloud.openfeign.ribbon.FeignLoadBalancer\#execute-》org.springframework.cloud.openfeign.ribbon.FeignLoadBalancer.RibbonRequest.client()->自定义实现ResetTimeoutFeignClient\#execute-》自定义实现JettyHttpClient\#execute-〉org.eclipse.jetty.client.HttpRequest\#send(org.eclipse.jetty.client.api.Response.CompleteListener)-》请求完成回调org.eclipse.jetty.client.util.FutureResponseListener\#onComplete-》将org.eclipse.jetty.client.HttpResponse封装为org.eclipse.jetty.client.HttpContentResponse\#HttpContentResponse->自定义实现JettyHttpClient\#toFeignResponse（代码见下方）-》org.springframework.cloud.openfeign.ribbon.FeignLoadBalancer\#execute将Response封装为RibbonResponse->feign.SynchronousMethodHandler\#decode

return Response.builder().status(status).reason(reason).headers(headers).request(feignRequest).body(body).build();

查看所有自定义实现的类没有重写Content-Type header的类，故而排除

#### 服务端 ####

##### 处理流程 #####

1.  接收派发请求：org.springframework.web.servlet.DispatcherServlet\#doDispatch
2.  根据请求查找处理句柄：org.springframework.web.servlet.DispatcherServlet\#getHandler
3.  查找Handler适配器（即目标方法适配器）：org.springframework.web.servlet.DispatcherServlet\#getHandlerAdapter
4.  预处理句柄回调：org.springframework.web.servlet.HandlerExecutionChain\#applyPreHandle-》org.springframework.web.servlet.HandlerInterceptor\#preHandle
5.  实际执行处理句柄：org.springframework.web.servlet.HandlerAdapter\#handle
6.  回处理完成后置调拦截器：org.springframework.web.servlet.HandlerInterceptor\#postHandle
7.  处理派发请求处理结果：org.springframework.web.servlet.DispatcherServlet\#processDispatchResult
    
    1.  如果存在异常则处理：org.springframework.web.servlet.DispatcherServlet\#processHandlerException
    2.  如果存在ModelAndView，则渲染mv：org.springframework.web.servlet.DispatcherServlet\#render
    3.  如果是并发异步处理则返回
    4.  否则回调拦截器：org.springframework.web.servlet.HandlerInterceptor\#afterCompletion
8.  如果是并发异步处理则回调拦截器：org.springframework.web.servlet.AsyncHandlerInterceptor\#afterConcurrentHandlingStarted
9.  如果是multipart请求清理multipart：org.springframework.web.servlet.DispatcherServlet\#cleanupMultipart
10. 发布事件：org.springframework.web.servlet.FrameworkServlet\#publishRequestHandledEvent
11. javax.servlet.FilterChain

##### 实际执行处理句柄 #####

org.springframework.web.servlet.DispatcherServlet\#doDispatch->org.springframework.web.servlet.HandlerAdapter\#handle

1.  org.springframework.web.servlet.HandlerAdapter\#handle，当前案例实现类：org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter-》org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter\#handle
2.  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter\#handleInternal
3.  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter\#invokeHandlerMethod
    
    1.  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter\#getDataBinderFactory
    2.  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter\#getModelFactory
    3.  org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter\#createInvocableHandlerMethod
    4.  设置argumentResolvers（见图1）
    5.  设置returnValueHandlers（见图2）
    6.  设置parameterNameDiscoverer：org.springframework.core.DefaultParameterNameDiscoverer
    7.  设置ignoreDefaultModelOnRedirect，默认true
    8.  设置asyncRequestTimeout，默认null
    9.  设置TaskExecutor：new SimpleAsyncTaskExecutor(“MvcAsync”)
    10. 注册callableInterceptors，默认空数组：CallableProcessingInterceptor
    11. 注册deferredResultInterceptors，默认空数组：DeferredResultProcessingInterceptor
    12. 执行目标方法：org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod\#invokeAndHandle
    13. 反射调用目标方法，得到返回值
    14. 如果返回值为空或者responseStatusReason不为空设置setRequestHandled后返回
    15. 选择支持返回值类型的处理句柄：org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite\#selectHandler，当前案例：org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor
    16. 回调返回值拦截器：org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite\#handleReturnValue，当前案例：org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor\#handleReturnValue
    17. 创建输入输出消息对象：org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver\#createInputMessage，org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor\#createOutputMessage
    18. 写入数据：org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor\#writeWithMessageConverters(T, org.springframework.core.MethodParameter, org.springframework.http.server.ServletServerHttpRequest, org.springframework.http.server.ServletServerHttpResponse)
    19. 如果是isResourceType，写入header：Accept-Ranges，存在异常则写入header：Content-Range，当前案例：否
    20. 如果outputMessage存在Content-Type则使用，当前案例：不存在
    21. 否则获取request请求的Accept类型org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor\#getAcceptableMediaTypes
    22. 获取请求producible类型（对应注解produces属性：@PostMapping(value = “/hello”, produces = “application/json;charset=utf8”)）rg.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor\#getProducibleMediaTypes(javax.servlet.http.HttpServletRequest, java.lang.Class<?>, java.lang.reflect.Type)：当前案例请求中org.springframework.web.servlet.HandlerMapping\#PRODUCIBLE\_MEDIA\_TYPES\_ATTRIBUTE参数不存在，走兜底：org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver\#allSupportedMediaTypes
    23. 根据请求方acceptableTypes获取可兼容的producibleTypes作为可使用的Content-Type MediaType列表：mediaTypesToUse，当前案例：Content-Type列表见：注释1
    24. 排序可兼容的mediaTypes：org.springframework.http.MediaType\#sortBySpecificityAndQuality，排序结果见：注释2
    25. 选择第一个具体的MediaType：org.springframework.util.MimeType\#isConcrete
    26. 获取匹配的转换器：org.springframework.http.converter.HttpMessageConverter，当前案例：org.springframework.http.converter.json.MappingJackson2HttpMessageConverter
    27. 写入body前置通知回调：org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice\#beforeBodyWrite
    28. 如果存在则写入Response header：Content-Disposition
    29. 写入body数据：MappingJackson2HttpMessageConverter-》org.springframework.http.converter.AbstractGenericHttpMessageConverter\#write
    30. 添加默认header：org.springframework.http.converter.AbstractHttpMessageConverter\#addDefaultHeaders，Content-Type，Content-Length（当前案例均为null不写入：org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter\#getContentLength）
    31. 向outputMessage写入body数据：org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter\#writeInternal
    32. 构建ModelAndView：org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter\#getModelAndView
4.  请求完成后置处理：org.springframework.web.context.request.AbstractRequestAttributes\#requestCompleted
5.  如果Response不包含header（Cache-Control），并且org.springframework.web.method.annotation.SessionAttributesHandler\#hasSessionAttributes，处理cache：org.springframework.web.servlet.support.WebContentGenerator\#applyCacheSeconds(javax.servlet.http.HttpServletResponse, int)
6.  否则准备Response：org.springframework.web.servlet.support.WebContentGenerator\#prepareResponse
    
    1.  cacheControl不为空，则设置header（Cache-Control），或header（Pragma），或header（Expires）
    2.  否则设置header（Cache-Control），或header（Pragma），或header（Expires）为指定值，例如：no-cache，no-store，1L
    3.  如果varyByRequestHeaders不为空，设置header（Vary）

#### 问题原因 ####

响应体如果没有指定Content-Type，那么就会从兼容请求体Accept的Content-Type中选择一个进行响应，也就是说请求方使用了非json格式的Accept引起，为了验证问题，我们查看线上pinpoint（开源的链路监控平台）监控，出现问题的请求的Accept header如下，与报错原因也就对应上了

accept=text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7

### 解决方法 ###

1.  请求方使用适配的Accept类型，例如：application/json;charset=utf8或\*/\*
2.  接口PostMapping/RequestMapping等注解增加配置  
    a. 下游接口可以增加produces配置响应内容为json格式，即content-type header：org.springframework.web.bind.annotation.PostMapping\#produces  
    b. 上游接口可以增加consumes配置请求内容为json格式，即accept header：org.springframework.web.bind.annotation.PostMapping\#consumes
3.  实现接口org.springframework.http.converter.HttpMessageConverter\#write写入OutMessage Content-Type，例如：open-feign在编译时写入header：org.springframework.cloud.openfeign.support.SpringEncoder\#encode-》write，服务端是在将return type写入outputMessage时处理（Writes the given return type to the given output message）：org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor\#writeWithMessageConverters(T, org.springframework.core.MethodParameter, org.springframework.http.server.ServletServerHttpRequest, org.springframework.http.server.ServletServerHttpResponse)
4.  为OutputMessage设置适配的Content-Type header org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor\#createOutputMessage
    
    1.  增加自定义ServletHandler，例如：xxl-job中的方法，代码见附件3
    2.  实现预处理handle拦截器处理：org.springframework.web.servlet.HandlerInterceptor\#preHandle

注意：方法2-4要根据实际业务场景是否可以使用，客户端期望xhtml，但是实际响应json，是否有潜在的风险？  
Q&A

1.  接口PostMapping/RequestMapping等注解增加headers配置是否可以？org.springframework.web.bind.annotation.PostMapping\#headers
    
    1.  不可以，因为该header是添加再Request请求中，需要添加在Response中的header才可以

### 注释 ###

注释1

0 = {
        MediaType@22077} "application/octet-stream"
    1 = {
        MediaType@22078} "text/plain"
    2 = {
        MediaType@22079} "application/xml"
    3 = {
        MediaType@22080} "text/xml"
    4 = {
        MediaType@22081} "application/x-www-form-urlencoded"
    5 = {
        MediaType@22082} "application/cbor"
    6 = {
        MediaType@22083} "application/*+xml"
    7 = {
        MediaType@22084} "multipart/form-data"
    8 = {
        MediaType@22085} "application/json"
    9 = {
        MediaType@22086} "application/*+json"
    10 = {
        MediaType@22057} "*/*"

注释2

0 = {
        MediaType@22085} "application/json"
    1 = {
        MediaType@22085} "application/json"
    2 = {
        MediaType@22082} "application/cbor"
    3 = {
        MediaType@22293} "application/xml"
    4 = {
        MediaType@22296} "application/xml"
    5 = {
        MediaType@22086} "application/*+json"
    6 = {
        MediaType@22292} "application/*+json"
    7 = {
        MediaType@22294} "text/xml"
    8 = {
        MediaType@22295} "application/*+xml"
    9 = {
        MediaType@22297} "text/xml"
    10 = {
        MediaType@22298} "application/*+xml"

### 附件 ###

图1  
![argumentResolvers.png][]  
图2  
![returnValueHandlers.png][]  
附件3  
![在这里插入图片描述][215e195c5d8c44c788c4b52d7b536706.png_pic_center]

[argumentResolvers.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/ca805358de5244069dff743169be91ab.png
[returnValueHandlers.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/49b0e32bc1734cc2b65f968e80716cf5.png
[215e195c5d8c44c788c4b52d7b536706.png_pic_center]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/26/030d1fd59e21473f96ce9578a3987d00.png