How to add data to the request header when feign is called remotely

1. Solutions to problems firstBy implementing Feign's RequestInterceptor (interceptor) interface, rewrite the apply method inside, and add custom request header parameters and data input to RequestTemplate.When the request first comes in, it will enter the interceptor, and when the business code makes a remote call, it will also enter the request.

@Componentpublic class FeignClientsExtendInterceptor implements RequestInterceptor {@Overridepublic void apply(RequestTemplate requestTemplate) {// This method is thread safeServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();// When it is not empty, take out the header in the request and set it to the feign request as it isif (null != attributes) {HttpServletRequest request = attributes.getRequest();if (null != request) {// Traversing the settings can also take the entire Header from the request and write it to the RequestTemplateEnumeration headerNames = request.getHeaderNames();if (headerNames != null) {while (headerNames.hasMoreElements()) {String name = headerNames.nextElement();String values ​​= request.getHeader(name);requestTemplate.header(name, values);}}}}// Process the request body parameter information// When feign calls the get interface, it will report a 405 Request method 'POST' not supported error// When you don't need to transmit the information in the request body, you can solve it by commenting the code that processes the request body information// The reason is that when feign sends a request at the bottom layer, it finds that the request body with parameters will be automatically converted into a post request./*Enumeration bodyNames = request.getParameterNames();StringBuilder body = new StringBuilder();if (bodyNames != null) {while (bodyNames.hasMoreElements()) {String name = bodyNames.nextElement();String values ​​= request.getParameter(name);body.append(name).append("=").append(values).append("&");}}if (body.length() != 0) {body.deleteCharAt(body.length() - 1);requestTemplate.body(body.toString());}*/}}

2. Business scenario (to ensure that the caller's information is consistent in subsequent requests)

(1) MQ messages are consumed and remote calls are initiated.

That is, there is no request-related information at this time, but when feign initiates a request, it is necessary to ensure that the information in the request header is the relevant information of the current thread. At this time, the required relevant information can be put into a thread copyIn the middle, by inheriting RequestContextHolder or rewriting a similar class, put the information of the current thread in, and then when feign initiates a remote call, take out the required information and put it into the request header.

(2) Same thread

When the front-end request is made, it will bring a series of verification parameters in the request header, call my service, and need to call other services.In other services, it is necessary to extract or verify the information in the request header.

When feign is called remotely, the bottom layer is to encapsulate the parameters and then make a request. It is a new request, so the header file information in the incoming request from the front end will not be passed, so you can rewrite the RequestInterceptor,Copy the information in the request header intact.

(3) Multi-threaded asynchronous calls to other microservices

The above rewritten code may not be able to obtain the request information of the main thread. The main reason is: RequestContextHolder to obtain the request information. When an asynchronous call is found, after the main thread ends, the child thread cannot obtain the request and will reporterror message.

Solution 1:

By obtaining the request of the main thread, when the front-end call is made, the front-end request will come in. At this time, the sub-thread sharing is enabled, then when the subsequent business is executed, when the asynchronous call is found, after the main thread ends, the sub-thread isInformation about the request can be obtained.

ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();// Enable child thread sharing after the above codeRequestContextHolder.setRequestAttributes(servletRequestAttributes,true);//Set child thread sharing

Solution 2:

    is similar to the processing method of (2) the same thread, put the request and session information of the main thread into ThreadLocal, and transparently transmit it to the child thread to obtain it.