Different calling forms of REST services with Feign client in Spring Cloud

1. Calling a REST service with Query Params

In Spring Cloud, you can send your query params with org.springframework.cloud.openfeign.SpringQueryMap annotation.

In your back-end code, you should use MultiValueMap and LinkedMultiValueMap. Key must be string.

MultiValueMap<String, String> params = new LinkedMultiValueMap<String, String>();
params.add("Name", "Ilhan");
params.add("Number", 26);
ResponseEntity<String> getRestServiceName1Response= feignClient.postRestServiceName1(params, "HEADER_VALUE");

In your feign client code,

@GetMapping(value = "${rest.service.name1}",
consumes = MediaType.APPLICATION_XML_VALUE,
produces = MediaType.APPLICATION_XML_VALUE)
public ResponseEntity<String> getRestServiceName1(
@SpringQueryMap MultiValueMap<String, String> params,
@RequestHeader(Constants.HEADER_NAME) String headerValue);

Consumes value will set HTTP Content-Type field of your request. Produces value will set HTTP Accept field of your request. With Content-Type field, you say content type of request body . With Accept field, you say content type of response body which you will be able to consume. Value of PostMapping|GetMapping|etc may be loaded from external properties.

2. Calling a REST service with string body

@PostMapping(value ="${rest.service.name2}", 
consumes = MediaType.APPLICATION_XML_VALUE, 
produces = MediaType.APPLICATION_XML_VALUE)
public ResponseEntity<String> postRestServiceName2(
@RequestBody String request,
@RequestHeader(Constants.HEADER_NAME) String headerValue);

3. Calling a REST service with APPLICATION_FORM_URLENCODED_VALUE

@PostMapping(value = "${rest.service.name3}", consumes = APPLICATION_FORM_URLENCODED_VALUE)
public ResponseEntity<String> postRestServiceName3(@RequestBody Map<String, ?> params);

You should use Map<String, ?> type param and also org.springframework.web.bind.annotation.RequestBody annotation.

It will continue…