Feign: Allow to customize encoding process of path params

[tjuchniewicz]

Currently Encoder is applied only for @RequestBody params. What about @RequestParam?

I know this is special case but we have lot of working legacy code. For current solution this objects are serialized using Jackson (we use @JsonValue) but Feign uses simple toString().

Possible solutions:

• invoke Encoder for all parameter types
• use Jackson to serialize object

[rmaciej1983]

If you use @FeignClient and Spring Cloud Netflix you can use org.springframework.cloud.netflix.feign.FeignFormatterRegistrar.
You should create a bean in client's configuration:

@Bean
public FeignFormatterRegistrar localDateFeignFormatterRegistrar() {
     return new FeignFormatterRegistrar() {
         @Override
         public void registerFormatters(FormatterRegistry formatterRegistry) {
            //Here should be some code.
          }
     };
}

In registerFormatters() method you have access to object of FormatterRegistry.
If you look inside the FormatterRegistry class, you will see a method:

void addFormatterForFieldType(Class<?> fieldType, Printer<?> printer, Parser<?> parser);

This is a method that will let you to associate specific class with a printer (for building a string from an object) and parser (for building an object from a string).

[tjuchniewicz]

FeignFormatterRegistrar has some minor side-effect when encoding object and its fields for example Pageable. Using encoder we can encode to &size=10&page=1 but using FeignFormatterRegistrar we can encode only to &pageable=true&size=10&page=1 which introduces unnecessary url parameter pageable=true.

[spencergibb]

This is not the forum to discuss FeignFormatterRegistrar and other spring cloud Netflix things

[rage-shadowman]

Using JSON for request params seems like a bad design to me. However, since you need to... Why doesn't @Param(expander = MyJsonTextExpander.class) work for you?

[kdavisk6]

Since this issue is related primarily to Spring, I'm going to close this. If this comes up again and is related to Param.Expander, I'll reconsider.