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SpringCloud Feign传递HttpServletRequest对象流程

作者：小白的救赎

HttpServletRequest接口的对象代表客户端的请求，当客户端通过HTTP协议访问Tomcat服务器时，HTTP请求中的所有信息都封装在HttpServletRequest接口的对象中，这篇文章介绍了Feign传递HttpServletRequest对象的流程，感兴趣的同学可以参考下文

这里我的业务场景是：在请求头中获取服务端登录时传给客户端的token，并且客户端将token放在请求头中。以至于我需要在参数传递上传入HttpServletRequest。如果你非要向我一样传入HttpServletRequest对象那么就往下看，当然你如果可以改成其他参数传递就不需要往下看了。

使用Feign所需要的必需知识别忘记：

一、需要在调用方以及被调用方以及Feign接口模块引入依赖

二、被调用方与调用方的主启动类均需要加上@EnableFeignClients注解

三、被调用方的注解后面还需要加扫描路径，对于我本人项目则是@EnableFeignClients(basePackages = "com.chf")

四、被调用方的控制层(Controller)的方法需要是public。因为写在Feign接口中的方法就是默认的public static final。所以说两个的访问权限修饰符必须是一致的。

五、将被调用方的方法copy到Feign接口中，这里需要注意三点：

feign.codec.EncodeException: Could not write JSON: getInputStream() has already been called for this request; nested exception is com.fasterxml.jackson.databind.JsonMappingException: getInputStream() has already been called for this request (through reference chain: org.apache.catalina.connector.RequestFacade["reader"])
    at feign.ReflectiveFeign$BuildEncodedTemplateFromArgs.resolve(ReflectiveFeign.java:376)
    at feign.ReflectiveFeign$BuildTemplateByResolvingArgs.create(ReflectiveFeign.java:224)
    at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:75)
    at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103)
    at com.sun.proxy.$Proxy81.concertCount(Unknown Source)
    at com.chf.service.impl.ApiEChartsServiceImpl.ticketCount(ApiEChartsServiceImpl.java:25)
    at com.chf.controller.api.ApiEChartsController.ticketCount(ApiEChartsController.java:25)
    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:190)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:888)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:526)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1579)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)
Caused by: org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: getInputStream() has already been called for this request; nested exception is com.fasterxml.jackson.databind.JsonMappingException: getInputStream() has already been called for this request (through reference chain: org.apache.catalina.connector.RequestFacade["reader"])
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:296)
    at org.springframework.http.converter.AbstractGenericHttpMessageConverter.writeInternal(AbstractGenericHttpMessageConverter.java:113)
    at org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:227)
    at org.springframework.cloud.openfeign.support.SpringEncoder.encode(SpringEncoder.java:114)
    at feign.ReflectiveFeign$BuildEncodedTemplateFromArgs.resolve(ReflectiveFeign.java:372)
    ... 56 more
Caused by: com.fasterxml.jackson.databind.JsonMappingException: getInputStream() has already been called for this request (through reference chain: org.apache.catalina.connector.RequestFacade["reader"])
    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:394)
    at com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:353)
    at com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:316)
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:729)
    at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:166)
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480)
    at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319)
    at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1433)
    at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:921)
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:287)
    ... 60 more
Caused by: java.lang.IllegalStateException: getInputStream() has already been called for this request
    at org.apache.catalina.connector.Request.getReader(Request.java:1208)
    at org.apache.catalina.connector.RequestFacade.getReader(RequestFacade.java:504)
    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 com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:688)
    at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:721)
    ... 66 more

报这个错误的原因主要是：Feign没有接受HttpServletRequest参数。以下三点是处理这个问题的解决办法。

一、在Feign模块中写一个配置类实现RequestInterceptor重写apply()方法。

二、修改Feign接口中的两处地方。

三、在调用方调用Feign接口地方改为请求头中的参数。

@Component
public class FeignConfig implements RequestInterceptor {
    @Override
    public void apply(RequestTemplate requestTemplate) {
        ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        HttpServletRequest request = attributes.getRequest();
        requestTemplate.header("token",request.getHeader("token"));
    }
}
@Component
// 第一处更改的位置：加上configuration
@FeignClient(value = "service:application:name",configuration = FeignConfig.class)
public interface FeignClient {
    @GetMapping("全路径名")
    // 第二处更改的位置：加上@RequestHeader注解并且带上需要的请求头类型
    Integer count(@RequestHeader("token") String token);
}
@Service
public class AServiceImpl implements AService {
    @Autowired
    private FeignClient feignClient;
    @Override
    public Integer personCount(HttpServletRequest request) {
        String token = request.getHeader("token");
        return feignClient.count(token);
    }
}

到此这篇关于SpringCloud Feign传递HttpServletRequest对象流程的文章就介绍到这了,更多相关SpringCloud传递HttpServletRequest内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！

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