Fix: Property resolution for extensions within @OpenAPIDefinition Info object

springdoc-openapi-starter-common/src/main/java/org/springdoc/core/service/OpenAPIService.java

@@ -636,9 +636,11 @@ public Class<? extends Annotation> annotationType() {
 	 */
 	private void buildOpenAPIWithOpenAPIDefinition(OpenAPI openAPI, OpenAPIDefinition apiDef, Locale locale) {
 		boolean isOpenapi3 = propertyResolverUtils.isOpenapi31();
-		Map<String, Object> extensions = AnnotationsUtils.getExtensions(isOpenapi3, apiDef.info().extensions());
 		// info
-		AnnotationsUtils.getInfo(apiDef.info(), true).map(info -> resolveProperties(info, extensions, locale)).ifPresent(openAPI::setInfo);
+		AnnotationsUtils.getInfo(apiDef.info(), true).map(info -> {
+			Map<String, Object> extensions = AnnotationsUtils.getExtensions(isOpenapi3, apiDef.info().extensions());
+			return resolveProperties(info, extensions, locale);
+		}).ifPresent(openAPI::setInfo);
 		// OpenApiDefinition security requirements
 		securityParser.getSecurityRequirements(apiDef.security()).ifPresent(openAPI::setSecurity);
 		// OpenApiDefinition external docs
@@ -702,7 +704,7 @@ private Info resolveProperties(Info info, Map<String, Object> extensions, Locale
 			resolveProperty(contact::getUrl, contact::url, propertyResolverUtils, locale);
 		}
 
-		if (propertyResolverUtils.isResolveExtensionsProperties() && extensions != null) {
+		if (extensions != null) {
 			Map<String, Object> extensionsResolved = propertyResolverUtils.resolveExtensions(locale, extensions);
 			if (propertyResolverUtils.isOpenapi31())
 				extensionsResolved.forEach(info::addExtension31);
@@ -713,7 +715,6 @@ private Info resolveProperties(Info info, Map<String, Object> extensions, Locale
 		return info;
 	}
 
-
 	/**
 	 * Resolve property.
 	 *

springdoc-openapi-starter-common/src/main/java/org/springdoc/core/utils/PropertyResolverUtils.java

@@ -224,21 +224,27 @@ public Map<String, Object> resolveExtensions(Locale locale, Map<String, Object>
 			Map<String, Object> extensionsResolved = new HashMap<>();
 			extensions.forEach((key, value) -> {
 				String keyResolved = resolve(key, locale);
-				if (value instanceof HashMap<?, ?>) {
+				if (value instanceof HashMap<?, ?> valueAsMap) {
 					Map<String, Object> valueResolved = new HashMap<>();
-					((HashMap<?, ?>) value).forEach((key1, value1) -> {
+					valueAsMap.forEach((key1, value1) -> {
 						String key1Resolved = resolve(key1.toString(), locale);
 						String value1Resolved = resolve(value1.toString(), locale);
 						valueResolved.put(key1Resolved, value1Resolved);
 					});
 					extensionsResolved.put(keyResolved, valueResolved);
 				}
-				else
+				else if (value instanceof String valueAsString) {
+					String valueResolved = resolve(valueAsString, locale);
+					extensionsResolved.put(keyResolved, valueResolved);
+				}
+				else {
 					extensionsResolved.put(keyResolved, value);
+				}
 			});
 			return extensionsResolved;
 		}
-		else
+		else {
 			return extensions;
+		}
 	}
 }

springdoc-openapi-starter-webmvc-api/src/test/java/test/org/springdoc/api/v31/app245/HelloController.java

@@ -0,0 +1,30 @@
+package test.org.springdoc.api.v31.app245;
+
+import io.swagger.v3.oas.annotations.OpenAPIDefinition;
+import io.swagger.v3.oas.annotations.extensions.Extension;
+import io.swagger.v3.oas.annotations.extensions.ExtensionProperty;
+import io.swagger.v3.oas.annotations.info.Info;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@SpringBootApplication
+@OpenAPIDefinition(
+    info = @Info(
+        title = "My App",
+        version = "${springdoc.version}",
+        extensions = {
+            @Extension(properties = {
+                @ExtensionProperty(name = "x-build-time", value = "${git.build.time}")
+            })
+        }
+    )
+)
+@RestController
+public class HelloController {
+
+    @GetMapping("/hello")
+    public String hello() {
+        return "hello";
+    }
+}

springdoc-openapi-starter-webmvc-api/src/test/java/test/org/springdoc/api/v31/app245/SpringDocApp245Test.java

@@ -0,0 +1,31 @@
+package test.org.springdoc.api.v31.app245;
+
+import static org.hamcrest.Matchers.is;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.web.servlet.MockMvc;
+
+@SpringBootTest(properties = {
+    "springdoc.version=v1",
+    "git.build.time=2025-07-08T12:00:00Z"
+})
+@AutoConfigureMockMvc
+class SpringDocApp245Test {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Test
+    void SpringDocTestApp() throws Exception {
+        mockMvc.perform(get("/v3/api-docs"))
+            .andExpect(status().isOk())
+            .andExpect(jsonPath("$.info.version", is("v1")))
+            .andExpect(jsonPath("$.info.x-build-time", is("2025-07-08T12:00:00Z")));
+    }
+}