Feign Client with Spring Boot: RequestParam.value() was empty on parameter 0

Question

I created a simple Feign Client with Spring Boot like this:

@FeignClient("spring-cloud-eureka-client")
public interface GreetingClient {
    @RequestMapping("/greeting")
    String greeting(@RequestParam String name);
}

But when I try just to start an application I get an error:

java.lang.IllegalStateException: RequestParam.value() was empty on parameter 0

First I didn't understand what is the reason and googled a lot but didn't find an answer. Almost excidentely I figured out that it works if to write request param name explicitly:

@RequestParam("name") String name

So my question: is it a bug or could it be configured to not write request params names explicitly?

I believe there needs to be a jvm setting so the parameter names can be used with java 8. — spencergibb, Jun 01 '17 at 17:54
@spencergibb it works without any additional settings on the same jvm for a plain Spring rest controllers — Igorock, Jun 01 '17 at 17:57

yongsung.yoon · Accepted Answer · 2019-02-08T11:09:03.787

Both Spring MVC and Spring cloud feign are using the same ParameterNameDiscoverer - named DefaultParameterNameDiscoverer to find parameter name. It tries to find the parameter names with the following step.

First, it uses StandardReflectionParameterNameDiscoverer. It tries to find the variable name with reflection. It is only possible when your classes are compiled with -parameters.

Second, if it fails, it uses LocalVariableTableParameterNameDiscoverer. It tries to find the variable name from the debugging info in the class file with ASM libraries.

The difference between Spring MVC and Feign occurs here. Feign uses above annotations (like @RequestParam) on methods of Java interfaces. But, we use these on methods of Java classes when using Spring MVC. Unfortunately, javac compiler omits the debug information of parameter name from class file for java interfaces. That's why feign fails to find parameter name without -parameter.

Namely, if you compile your code with -parameters, both Spring MVC and Feign will succeed to acquire parameter names. But if you compile without -parameters, only Spring MVC will succeed.

As a result, it's not a bug. it's a limitation of Feign at this moment as I think.

Maven solution for spring boot 2: https://stackoverflow.com/questions/31845676/how-to-compile-spring-boot-applications-with-java-8-parameter-flag — Robin Bruneel, Mar 04 '19 at 13:50

score 33 · Answer 2 · answered Aug 30 '18 at 14:03

33

Just use String greeting(@RequestParam("name") String name);

    @FeignClient("spring-cloud-eureka-client")
    public interface GreetingClient {
       @RequestMapping("/greeting")
       String greeting(@RequestParam("name") String name);
    }

answered Aug 30 '18 at 14:03

Jebil

1,144
13
25

thanks it helped me , but why need to add @RequestParam("name") instead of @RequestParam , it should be by default take it right ? – Mosa Jan 26 '23 at 07:12
1

@Mosa check youngsung.yoon answer – Jebil Jan 26 '23 at 14:55

score 1 · Answer 3 · answered Sep 30 '22 at 08:44

This worked for me.

    @FeignClient(name="session-service", url="${session.host}")
    public interface SrocessingProxy {

    @RequestMapping(value = "/process/{key}", method = RequestMethod.POST)
    public Response processSession(@RequestParam String key, @RequestBody PayloadHolder payload);
    }
    
    //Service 
    @RequestMapping(value = "/process/{key}", method = RequestMethod.POST)
    public Response processSession(@RequestParam String key, @RequestBody PayloadHolder payload) { 
        System.out.print("Key : " + key);
    }

score 0 · Answer 4 · answered Dec 19 '20 at 03:44

0

I use upgrade maven-compiler-plugin to solve this plobrem. you can access: https://blog.51cto.com/thinklili/2566864

answered Dec 19 '20 at 03:44

LiLi

391
3
11

Feign Client with Spring Boot: RequestParam.value() was empty on parameter 0

4 Answers4

Linked