How to make GET requests to other Feign clients inside of a POST request?

Question

I have a REST API endpoint that makes use of several Feign clients to perform validation and processing. The endpoint in question accepts a POST request, but the Feign clients used for validation accept GET requests. When I make a POST request to my API endpoint I get the error below from the Feign clients that require a GET. I have my Feign clients methods annotated with @GetMapping, but it seems the request is still being sent as a POST. How do I make GET requests to Feign clients inside a POST request?

feign.FeignException: status 405 reading ValidationClient#checkData(String); content:
{"timestamp":"2018-08-06T14:43:45.998+0000","status":405,"error":"Method Not Allowed","message":"Request method 'POST' not supported","path":"/"}
    at feign.FeignException.errorStatus(FeignException.java:62) ~[feign-core-9.5.1.jar:na]
    at feign.codec.ErrorDecoder$Default.decode(ErrorDecoder.java:91) ~[feign-core-9.5.1.jar:na]
    at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:138) ~[feign-core-9.5.1.jar:na]
    at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:76) ~[feign-core-9.5.1.jar:na]
    at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103) ~[feign-core-9.5.1.jar:na]
    at com.sun.proxy.$Proxy129.checkFormat(Unknown Source) ~[na:na]
    at com.example.datainput.DataInputController.acceptData(DataInputController.java:20) ~[classes/:na]
    at sun.reflect.GeneratedMethodAccessor126.invoke(Unknown Source) ~[na:na]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:45005) ~[na:1.8.0_172]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_172]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:209) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:877) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:783) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:991) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:925) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:877) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:661) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851) ~[spring-webmvc-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.0.8.RELEASE.jar:5.0.8.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:96) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:40002) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:493) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:800) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:800) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1471) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_172]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_172]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.32.jar:8.5.32]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_172]

Edit:

Feign Client

@FeignClient("validation")
public interface ValidationClient {

    @GetMapping("/")
    boolean checkFormat(String data);

}

The controller of the client

@RestController
public class ValidationController {

    @Autowired
    ValidationProperties properties;

    @GetMapping("/")
    public boolean isValidFormat(@RequestParam String inputData) {
        return inputData.matches(properties.getValidFormat());
    }

}

The REST endpoint that uses the client

@RestController
public class DataInputController {

    @Autowired
    ValidationClient validationClient;

    @PostMapping("/")
    public String saveData(@RequestParam(name = "inputData") String inputData) {

        if (!validationClient.checkFormat(inputData)) {
            return "Invalid Format";
        }

        // save data here

        return "Input Success";
    }

}

I am using version FINCHLEY.SR1

Edit 2:

I've noticed that my Feign clients in my controller seem to be misconfigured. They are of type HardCodedTarget and the url property just http://<service-name> (in this case http://validation), it doesnt actually point to the real service the client is supposed to be using.

Edit 3: I added Ribbon

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</dependency>

to my service applications and to my api that is using the Feign clients. Unfortunately I am still having the same issue. I have refreshed and rebuilt everything.

Edit 4: I have created a GitHub project for this question.

https://github.com/zero01alpha/spring-cloud-demo

the input-entry module uses the input-format and input-parse modules as Feign clients to validate the length and parse/print items of an input string. I have been using the alphabet as input so the minimum length for the input parameter is set to 26. input-format runs on port 8080, input-parse on 8081, and input-entry on 8082, all using the default path / as their only endpoint and requiring a request param named input. So to recreate the issue I'm having

1. Start Config server
2. Start Eureka Server
3. Start input-format service
4. Start input-parse service
5. Start input-entry service

Then, send a POST request to localhost:8082 with a request param of input that is at least 26 characters. When I do this I get this response body.

{
    "timestamp": "2018-08-09T13:29:34.536+0000",
    "status": 500,
    "error": "Internal Server Error",
    "message": "status 405 reading InputFormatClient#checkFormat(String); content:\n{\"timestamp\":\"2018-08-09T13:29:34.504+0000\",\"status\":405,\"error\":\"Method Not Allowed\",\"message\":\"Request method 'POST' not supported\",\"path\":\"/\"}",
    "path": "/"
}

Answer 1

It's a Feign bug on kotlin. When I try to send GET rq through Feign client on GET endpoint I have same error. FROM service:

nested exception is feign.FeignException$MethodNotAllowed: [405 Method Not Allowed] during [GET] to [http://host:9000/api/users] [HierarchyClient#getUserIdsByImei(List)]

TO service:

[org.springframework.web.HttpRequestMethodNotSupportedException: Request method 'POST' not supported]

To fix this problem you can use Spring Boot 3 version, or add this request mapping to requested endpoint:

@RequestMapping(value = ["/api/users"], method = [RequestMethod.GET, RequestMethod.POST])

and use @PostMappping for request to it:

@PostMapping("/api/users")

Answer 2

By default, any parameter to a feign method is treated as the body, so your checkFormat() method will send a post because it has a body (a get cannot). So this:

@FeignClient("input-format")
public interface InputFormatClient {

    @GetMapping("/")
    boolean checkFormat(String input);

}

Needs to be:

@FeignClient("input-format")
public interface InputFormatClient {

    @GetMapping("/")
    boolean checkFormat(@RequestParam("input") String input);

}

Also the other client needs to be updated similarly

@FeignClient("input-parse")
public interface InputParseClient {

    @GetMapping("/")
    Map<String, String> getParsedItems(@RequestParam("input") String input);

}