Add support for negated parameters in SpringMvcContract

- Added 'allowNegatedParams' configuration option to FeignClientProperties
- Modified SpringMvcContract to skip negated parameters when the feature is enabled
- Added tests for both enabled and disabled cases
- Updated documentation with usage examples

Author: kssumin

docs/modules/ROOT/pages/spring-cloud-openfeign.adoc

@@ -760,7 +760,38 @@ The params attribute also supports the use of multiple `key=value` or only one `
 - When `params = { "key1=v1", "key2=v2" }`, the request url is parsed as `/stores/storeId?key1=v1&key2=v2`.
 - When `params = "key"`, the request url is parsed as `/stores/storeId?key`.
 
+[[negated-params-support]]
+=== Negated Parameters Support
 
+Spring Cloud OpenFeign provides optional support for negated parameters in `@RequestMapping` annotations. By default, negated parameters (such as `params = {"!expiration"}` or `params = {"param!=value"}`) are not supported in Feign clients, resulting in an `IllegalArgumentException`.
+
+When sharing interfaces between server and client, negated parameters can be useful for disambiguation of request mappings on the server side. To allow the use of negated parameters in your Feign clients, set the following property:
+
+[source,yaml]
+----
+spring:
+  cloud:
+    openfeign:
+      client:
+        config:
+          feignName:
+            allowNegatedParams: true
+----
+
+When enabled, negated parameters will be silently ignored when creating the client request. This is the expected behavior since negated parameters are constraints used only on the server side to avoid ambiguous mappings.
+
+Global configuration is also supported:
+
+[source,yaml]
+----
+spring:
+  cloud:
+    openfeign:
+      client:
+        config:
+          default:
+            allowNegatedParams: true
+----
 
 [[feign-querymap-support]]
 === Feign @QueryMap support

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

@@ -45,6 +45,7 @@
  * @author Hyeonmin Park
  * @author Jasbir Singh
  * @author Dominique Villard
+ * @author kssumin
  */
 @ConfigurationProperties("spring.cloud.openfeign.client")
 public class FeignClientProperties {
@@ -66,6 +67,11 @@ public class FeignClientProperties {
 	 */
 	private boolean removeTrailingSlash;
 
+	/**
+	 * If {@code true}, negated parameters (those starting with '!') will be allowed.
+	 */
+	private boolean allowNegatedParams = false;
+
 	public boolean isDefaultToProperties() {
 		return defaultToProperties;
 	}
@@ -106,6 +112,14 @@ public void setRemoveTrailingSlash(boolean removeTrailingSlash) {
 		this.removeTrailingSlash = removeTrailingSlash;
 	}
 
+	public void setAllowNegatedParams(Boolean allowNegatedParams) {
+		this.allowNegatedParams = allowNegatedParams;
+	}
+
+	public boolean getAllowNegatedParams() {
+		return allowNegatedParams;
+	}
+
 	@Override
 	public boolean equals(Object o) {
 		if (this == o) {

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

@@ -89,6 +89,7 @@
  * @author Ram Anaswara
  * @author Sam Kruglov
  * @author Tang Xiong
+ * @author kssumin
  */
 public class SpringMvcContract extends Contract.BaseContract implements ResourceLoaderAware {
 
@@ -118,6 +119,8 @@ public class SpringMvcContract extends Contract.BaseContract implements Resource
 
 	private final boolean removeTrailingSlash;
 
+	private final boolean allowNegatedParams;
+
 	public SpringMvcContract() {
 		this(Collections.emptyList());
 	}
@@ -172,6 +175,25 @@ public SpringMvcContract(List<AnnotatedParameterProcessor> annotatedParameterPro
 		convertingExpanderFactory = new ConvertingExpanderFactory(conversionService);
 		this.decodeSlash = decodeSlash;
 		this.removeTrailingSlash = removeTrailingSlash;
+		this.allowNegatedParams = false;
+	}
+
+	@Deprecated(forRemoval = true)
+	public SpringMvcContract(List<AnnotatedParameterProcessor> annotatedParameterProcessors,
+							 ConversionService conversionService, boolean decodeSlash, boolean removeTrailingSlash,
+							 boolean allowNegatedParams) {
+		Assert.notNull(annotatedParameterProcessors, "Parameter processors can not be null.");
+		Assert.notNull(conversionService, "ConversionService can not be null.");
+
+		List<AnnotatedParameterProcessor> processors = getDefaultAnnotatedArgumentsProcessors();
+		processors.addAll(annotatedParameterProcessors);
+
+		annotatedArgumentProcessors = toAnnotatedArgumentProcessorMap(processors);
+		this.conversionService = conversionService;
+		convertingExpanderFactory = new ConvertingExpanderFactory(conversionService);
+		this.decodeSlash = decodeSlash;
+		this.removeTrailingSlash = removeTrailingSlash;
+		this.allowNegatedParams = allowNegatedParams;
 	}
 
 	public SpringMvcContract(List<AnnotatedParameterProcessor> annotatedParameterProcessors,
@@ -411,7 +433,11 @@ private void parseParams(MethodMetadata data, Method method, RequestMapping meth
 				data.template().query(resolve(nameValueResolver.getName()), resolve(nameValueResolver.getValue()));
 			}
 			else {
-				throw new IllegalArgumentException("Negated params are not supported: " + param);
+				// Negated parameter case
+				if (!this.allowNegatedParams) {
+					throw new IllegalArgumentException("Negated params are not supported: " + param);
+				}
+				// When allowed, negated params are skipped
 			}
 		}
 	}

spring-cloud-openfeign-core/src/test/java/org/springframework/cloud/openfeign/support/SpringMvcContractTests.java

@@ -84,6 +84,7 @@
  * @author Sam Kruglov
  * @author Bhavya Agrawal
  * @author Tang Xiong
+ * @author kssumin
  **/
 
 class SpringMvcContractTests {
@@ -769,6 +770,28 @@ void shouldSetPageableAsBodyWhenQueryMapParamPresent() {
 		assertThat(data.get(1).bodyIndex()).isEqualTo(0);
 	}
 
+	@Test
+	void testAllowNegatedParams() throws Exception {
+		contract = new SpringMvcContract(Collections.emptyList(), getConversionService(), true, false, true);
+
+		Method method = TestTemplate_ParseParams.class.getDeclaredMethod("notEqualParams");
+		MethodMetadata data = contract.parseAndValidateMetadata(method.getDeclaringClass(), method);
+
+		assertThat(data.template().url()).isEqualTo("/test");
+		assertThat(data.template().method()).isEqualTo("GET");
+	}
+
+	@Test
+	void testDisallowNegatedParams() throws Exception {
+		contract = new SpringMvcContract(Collections.emptyList(), getConversionService(), true, false, false);
+
+		Method method = TestTemplate_ParseParams.class.getDeclaredMethod("notEqualParams");
+
+		assertThatIllegalArgumentException().isThrownBy(() -> {
+			contract.parseAndValidateMetadata(method.getDeclaringClass(), method);
+		}).withMessageContaining("Negated params are not supported");
+	}
+
 	private ConversionService getConversionService() {
 		FormattingConversionServiceFactoryBean conversionServiceFactoryBean = new FormattingConversionServiceFactoryBean();
 		conversionServiceFactoryBean.afterPropertiesSet();