OpenFeign practice makes GET requests in Feign interface support POJO parameters through @SpringQueryMap annotation

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1. Problem description:

In one sentence: Does our FeignClient interface support POJO parameters under GET requests?

If the interface we call is a GET request, if we use @FeignClient to directly define POJO parameters, the code is as follows:

@FeignClient(name = "payment-service", contextId = "payment-core", path = "/payment")
public interface PaymentFeign {
  
    @GetMapping("/refund")
    RefundPaymentVo refund(RefundPaymentDto refundPaymentDto);
}
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The following error message will be reported:

feign.FeignException$MethodNotAllowed: [405] during [GET] to [http://payment-service/payment/refund] [PaymentFeign#refund(RefundPaymentDto)]: [{"timestamp":"2022-03-26T18:34:47.058+00:00","status":405,"error":"Method Not Allowed","path":"/payment/refund"}]
  at feign.FeignException.clientErrorStatus(FeignException.java:221)
  at feign.FeignException.errorStatus(FeignException.java:194)
  at feign.FeignException.errorStatus(FeignException.java:185)
  at feign.codec.ErrorDecoder$Default.decode(ErrorDecoder.java:92)
  at feign.AsyncResponseHandler.handleResponse(AsyncResponseHandler.java:96)
  at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:138)
  at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:89)
  at org.springframework.cloud.openfeign.FeignCircuitBreakerInvocationHandler.lambda$asSupplier$1(FeignCircuitBreakerInvocationHandler.java:112)
  at java.util.concurrent.FutureTask.run(FutureTask.java:266)
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
  at java.lang.Thread.run(Thread.java:748)
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Second, the solution:

OpenFeign @QueryMapannotations support using POJOs as GET parameter mappings. Unfortunately, the default OpenFeign QueryMap annotation is not compatible with Spring because it lacks valueproperties.

Spring Cloud OpenFeign provides equivalent @SpringQueryMapannotations for annotating POJO or Map parameters as query parameter mappings.

For example, RefundPaymentDtothe class defines parameters orderCodeand refundAmount:

@Data
public class RefundPaymentDto {
    /**
     * 订单号
     */
    private String orderCode;

    /**
     * 退款金额（单位：分）
     */
    private Integer refundAmount;
}
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The following feign clients use Paramsthis class via the annotation:@SpringQueryMap

@FeignClient(name = "payment-service", contextId = "payment-core", path = "/payment")
public interface PaymentFeign {
  
    @GetMapping("/refund")
    RefundPaymentVo refund(@SpringQueryMap RefundPaymentDto refundPaymentDto);
}
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If you need more control over the generated query parameter mapping, you can implement a custom QueryMapEncoderbean.

3. Summary:

@SpringQueryMapThe use of annotations simplifies our complex definition of GET parameters in FeignClient (if we can only use a single definition @RequestParam)

References: 1. Spring Cloud OpenFeign official documentation