fix post request with body processed twice in retry filter https://github.com/spring-cloud/spring-cloud-gateway/issues/1315

spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/AdaptCachedBodyGlobalFilter.java

@@ -70,11 +70,18 @@ public class AdaptCachedBodyGlobalFilter
 			return chain.filter(exchange);
 		}
 
+		final Mono<String> requestProcessingFinishedFlag = Mono
+				.just("requestProcessingFinishedFlag");
 		return ServerWebExchangeUtils
-				.cacheRequestBody(exchange,
-						(serverHttpRequest) -> chain.filter(
-								exchange.mutate().request(serverHttpRequest).build()))
-				.switchIfEmpty(chain.filter(exchange));
+				.cacheRequestBody(exchange, (serverHttpRequest) -> chain
+						.filter(exchange.mutate().request(serverHttpRequest).build())
+						// suppress empty mono response from FilteringWebHandler, see
+						// https://github.com/spring-cloud/spring-cloud-gateway/issues/1315
+						.then(requestProcessingFinishedFlag))
+				// when request body is empty - we return from cacheRequestBody() with
+				// empty mono - so we will process that request
+				.switchIfEmpty(chain.filter(exchange).then(requestProcessingFinishedFlag))
+				.then();
 	}
 
 	@Override

spring-cloud-gateway-core/src/test/java/org/springframework/cloud/gateway/filter/factory/RetryGatewayFilterFactoryIntegrationTests.java

@@ -27,6 +27,8 @@ import com.netflix.loadbalancer.ServerList;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.hamcrest.CoreMatchers;
+import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 
@@ -34,6 +36,7 @@ import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.SpringBootConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.rule.OutputCapture;
 import org.springframework.boot.web.server.LocalServerPort;
 import org.springframework.cloud.gateway.filter.GatewayFilter;
 import org.springframework.cloud.gateway.filter.factory.RetryGatewayFilterFactory.RetryConfig;
@@ -49,6 +52,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ActiveProfiles;
 import org.springframework.test.context.junit4.SpringRunner;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -63,8 +67,20 @@ import static org.springframework.boot.test.context.SpringBootTest.WebEnvironmen
 		"spring.cloud.gateway.httpclient.connect-timeout=500",
 		"spring.cloud.gateway.httpclient.response-timeout=2s" })
 @DirtiesContext
+// default filter AddResponseHeader suppresses bug
+// https://github.com/spring-cloud/spring-cloud-gateway/issues/1315,
+// so we use only PrefixPath filter
+@ActiveProfiles("only-prefix-filter")
 public class RetryGatewayFilterFactoryIntegrationTests extends BaseWebClientTests {
 
+	@Rule
+	public final OutputCapture capture = new OutputCapture();
+
+	@Before
+	public void before() {
+		capture.reset();
+	}
+
 	@Test
 	public void retryFilterGet() {
 		testClient.get().uri("/retry?key=get").exchange().expectStatus().isOk()
@@ -115,6 +131,17 @@ public class RetryGatewayFilterFactoryIntegrationTests extends BaseWebClientTest
 				.exchange().expectStatus().isOk().expectBody(String.class).isEqualTo("3");
 	}
 
+	@Test
+	public void retryFilterPostOneTime() {
+		testClient.post().uri(
+				"/retrypost?key=retryFilterPostOneTime&expectedbody=HelloGateway&count=1")
+				.header(HttpHeaders.HOST, "www.retrypostconfig.org")
+				.syncBody("HelloGateway").exchange().expectStatus().isOk();
+		assertThat(this.capture.toString()).contains("setting new iteration in attr 0");
+		assertThat(this.capture.toString())
+				.doesNotContain("setting new iteration in attr 1");
+	}
+
 	@Test
 	public void retriesSleepyRequest() throws Exception {
 		testClient.mutate().responseTimeout(Duration.ofSeconds(10)).build().get()

spring-cloud-gateway-core/src/test/resources/application-only-prefix-filter.yml

@@ -0,0 +1,5 @@
+spring:
+  cloud:
+    gateway:
+      default-filters:
+        - PrefixPath=/httpbin