Spring Cloud Feign Client 上传文件

青旅半醒 2022-05-28 05:39 136阅读 0赞

项目是用Spring Cloud搭的微服务，使用了eureka，FeignClient。今天在做上传文件功能时，直接使用FeignClient去远程调用注册中心上的上传文件接口，一直报错。

解决方案：

加入maven依赖

<dependency>  
    	<groupId>io.github.openfeign.form</groupId>  
    	<artifactId>feign-form-spring</artifactId>  
    	<version>3.2.2</version>  
    </dependency>  
    <dependency>  
    	<groupId>io.github.openfeign.form</groupId>  
    	<artifactId>feign-form</artifactId>  
    	<version>3.2.2</version>  
    </dependency>

FeignClient接口里方法参数是文件类型的要用@RequestPart注解，且要设置ContentType为multipart/form-data

@FeignClient(value = "quote-service/api/attendance", configuration = IFeignAttendanceService.MultipartSupportConfig.class)
    public interface IFeignAttendanceService {
    	
        @PostMapping(value = "uploadFile", consumes = MediaType.MULTIPART_FORM_DATA )
        Object uploadFile(@RequestPart(value = "file") MultipartFile file, @RequestParam("prefixName") String prefixName);
    
        @Configuration
        class MultipartSupportConfig {
            @Bean
            public Encoder feignFormEncoder() {
                return new SpringFormEncoder();
            }
        }
    }

上面的MultipartSupportConfig 类也可以单独作为一个类，这里为了省事，用了内部类。

通过测试后发现，该方案确实可以上传文件，但是当我的接口参数使用实体类接收时，会抛如下异常：

2018-04-04 09:52:13.410 [http-nio-8720-exec-1] ERROR o.a.c.c.C.[.[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is feign.codec.EncodeException: class cn.erongcai.hrplatform.entity.Quote is not a type supported by this encoder.] with root cause
    feign.codec.EncodeException: class cn.erongcai.hrplatform.entity.Quote is not a type supported by this encoder.
    	at feign.codec.Encoder$Default.encode(Encoder.java:90)
    	at feign.form.FormEncoder.encode(FormEncoder.java:87)
    	at feign.form.spring.SpringFormEncoder.encode(SpringFormEncoder.java:64)
    	at feign.ReflectiveFeign$BuildEncodedTemplateFromArgs.resolve(ReflectiveFeign.java:350)
    	at feign.ReflectiveFeign$BuildTemplateByResolvingArgs.create(ReflectiveFeign.java:213)
    	at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:72)
    	at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103)
    	at com.sun.proxy.$Proxy96.saveQuote(Unknown Source)
    	at cn.erongcai.hrplatform.web.FeignQuoteController.saveQuote(FeignQuoteController.java:45)
    	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:498)
    	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
    	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
    	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116)
    	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
    	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
    	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    	at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:105)
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    	at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
    	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
    	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:474)
    	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
    	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:783)
    	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:798)
    	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1434)
    	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    	at java.lang.Thread.run(Thread.java:748)

为什么会抛异常呢，查看SpringFormEncoder类的源码：

public class SpringFormEncoder extends FormEncoder
    {
    
        public SpringFormEncoder()
        {
            this(((Encoder) (new feign.codec.Encoder.Default())));
        }
    
        public SpringFormEncoder(Encoder delegate)
        {
            super(delegate);//调用父类的构造方法
            MultipartFormContentProcessor processor = (MultipartFormContentProcessor)getContentProcessor(ContentType.MULTIPART);
            processor.addWriter(new SpringSingleMultipartFileWriter());
            processor.addWriter(new SpringManyMultipartFilesWriter());
        }
    
        public void encode(Object object, Type bodyType, RequestTemplate template)
            throws EncodeException
        {
            if(!bodyType.equals(org/springframework/web/multipart/MultipartFile))
            {
                super.encode(object, bodyType, template);//调用FormEncoder对应方法
                return;
            } else
            {
                MultipartFile file = (MultipartFile)object;
                java.util.Map data = Collections.singletonMap(file.getName(), object);
                super.encode(data, MAP_STRING_WILDCARD, template);
                return;
            }
        }
    }

我们可以发现SpringFormEncoder的encode方法当传送的对象不是MultipartFile的时候，就会调用super.encode， 也就是FormEncoder的encode方法。

FormEncoder类的部分源码：

public FormEncoder()
        {
            this(((Encoder) (new feign.codec.Encoder.Default())));
        }
    
        public FormEncoder(Encoder delegate)
        {
            _flddelegate = delegate;
            List list = Arrays.asList(new ContentProcessor[] {
                new MultipartFormContentProcessor(delegate), new UrlencodedFormContentProcessor()
            });
            processors = new HashMap(list.size(), 1.0F);
            ContentProcessor processor;
            for(Iterator iterator = list.iterator(); iterator.hasNext(); processors.put(processor.getSupportedContentType(), processor))
                processor = (ContentProcessor)iterator.next();
    
        }
    
        public void encode(Object object, Type bodyType, RequestTemplate template)
            throws EncodeException
        {
            String contentTypeValue = getContentTypeValue(template.headers());//这里会去到@PostMapping中consumes的值，所以参数需要传对象时指定一下consumes
            ContentType contentType = ContentType.of(contentTypeValue);//为啥指定consumes，是因为不指定就是application/x-www-form-urlencoded，而且processors中也包含，为啥包含见FormEncoder的构造函数
            if(!MAP_STRING_WILDCARD.equals(bodyType) || !processors.containsKey(contentType))
            {
                _flddelegate.encode(object, bodyType, template);//_flddelegate是啥呢，是SpringFormEncoder传递过来，也就是new Encoder.Default()
                return;
            }
            Charset charset = getCharset(contentTypeValue);
            Map data = (Map)object;
            try
            {
                ((ContentProcessor)processors.get(contentType)).process(template, charset, data);
            }
            catch(Exception ex)
            {
                throw new EncodeException(ex.getMessage());
            }
        }

FormEncoderr的encode方法当传送的对象是json格式的字符串的时候，就会调用 \_flddelegate.encode，即Encoder.Default的encode方法，而这个Encoder.Default的encode方法判断传送的类型不是String或者byte\[\]，就会抛异常

public interface Encoder
    {
        public static class Default
            implements Encoder
        {
    
            public void encode(Object object, Type bodyType, RequestTemplate template)
            {
                if(bodyType == java/lang/String)
                    template.body(object.toString());
                else
                if(bodyType == [B)
                    template.body((byte[])(byte[])object, null);
                else
                if(object != null)//当我们用对象传递参数的时候，会走这里
                    throw new EncodeException(String.format("%s is not a type supported by this encoder.", new Object[] {
                        object.getClass()
                    }));
            }
    
            public Default()
            {
            }
        }
    
    
        public abstract void encode(Object obj, Type type, RequestTemplate requesttemplate)
            throws EncodeException;
    
        public static final Type MAP_STRING_WILDCARD = Util.MAP_STRING_WILDCARD;
    
    }

因为我的项目中有很多接口用实体类作为接收参数的，所以上述解决方案无法满足我的要求。所以只能继续各种百度、各种谷歌，终于找到了合适的解决方案。

解决方案一：继续使用前面提到的方案，如果引用该配置类的FeignClient中，没有使用实体类作为参数的接口，则去掉配置类上的注解@Configuration就可以了，去掉注解@Configuration之后，该配置就只对通过configuration属性引用该配置的FeignClient起作用(或者将该文件上传接口单独放到一个FeignClient中，去掉配置类上的注解@Configuration)。

方案一只支持文件上传，如果引用该配置的FeignClient中有使用实体类作为参数接收的接口，则调用该接口时会抛异常。

解决方案二：继续使用前面提到的方案，将配置文件修改为如下：

@Configuration
    class MultipartSupportConfig {
    	@Autowired
    	private ObjectFactory<HttpMessageConverters> messageConverters;
    		
        @Bean
        public Encoder feignFormEncoder() {
            return new SpringFormEncoder(new SpringEncoder(messageConverters));
        }
     }

方案二既支持文件上传也支持实体类作为参数接收。