Resolve placeholders before parsing request headers

spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/support/SpringMvcContract.java

@@ -404,6 +404,7 @@ private void parseHeaders(MethodMetadata md, RequestMapping annotation) {
 		// TODO: only supports one header value per key
 		if (annotation.headers() != null) {
 			for (String header : annotation.headers()) {
+				header = resolve(header);
 				int index = header.indexOf('=');
 				if (!header.contains("!=") && index >= 0) {
 					md.template()

spring-cloud-openfeign-core/src/test/java/org/springframework/cloud/openfeign/valid/ValidFeignClientTests.java

@@ -185,6 +185,13 @@ void testHeaderPlaceholders() {
 		assertThat(header).as("header was wrong").isEqualTo("myPlaceholderHeaderValue");
 	}
 
+	@Test
+	void testHeaderPlaceholderExpression() {
+		String header = testClient.getHelloHeadersPlaceholderExpression();
+		assertThat(header).as("header was null").isNotNull();
+		assertThat(header).as("header was wrong").isEqualTo("myPlaceholderHeaderValue");
+	}
+
 	@Test
 	void testFeignClientType() {
 		assertThat(feignClient).isInstanceOf(FeignBlockingLoadBalancerClient.class);
@@ -453,6 +460,9 @@ protected interface TestClient {
 				headers = "myPlaceholderHeader=${feignClient.myPlaceholderHeader}")
 		String getHelloHeadersPlaceholders();
 
+		@GetMapping(path = "/helloheadersplaceholders", headers = "${feignClient.placeholderHeader}")
+		String getHelloHeadersPlaceholderExpression();
+
 		@GetMapping("/helloparams")
 		List<String> getParams(@RequestParam("params") List<String> params);
 

spring-cloud-openfeign-core/src/test/resources/application.yml

@@ -20,6 +20,7 @@ feignClient:
   localappName: localapp
   methodLevelRequestMappingPath: /hello2
   myPlaceholderHeader: myPlaceholderHeaderValue
+  placeholderHeader: myPlaceholderHeader=myPlaceholderHeaderValue
 management.endpoints.web.expose: '*'
 
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