Sets spring.servlet.multipart.enabled to false by default.

Fixes gh-3527

spring-cloud-gateway-server-mvc/src/main/java/org/springframework/cloud/gateway/server/mvc/common/MultipartEnvironmentPostProcessor.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package org.springframework.cloud.gateway.server.mvc.common;
+
+import java.util.Map;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.env.EnvironmentPostProcessor;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.MapPropertySource;
+import org.springframework.util.StringUtils;
+
+public class MultipartEnvironmentPostProcessor implements EnvironmentPostProcessor {
+
+	/* for testing */ static final String MULTIPART_ENABLED_PROPERTY = "spring.servlet.multipart.enabled";
+	/* for testing */ static final String MULTIPART_PROPERTY_SOURCE_NAME = "gatewayServerWebmvcMultipartPropertySource";
+
+	@Override
+	public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
+		String multipartEnabled = environment.getProperty(MULTIPART_ENABLED_PROPERTY);
+		if (!StringUtils.hasText(multipartEnabled)) {
+			// no user set property, set it to false.
+			MapPropertySource propertySource = new MapPropertySource(MULTIPART_PROPERTY_SOURCE_NAME,
+					Map.of(MULTIPART_ENABLED_PROPERTY, Boolean.FALSE));
+			environment.getPropertySources().addFirst(propertySource);
+		}
+	}
+
+}

spring-cloud-gateway-server-mvc/src/main/resources/META-INF/spring.factories

@@ -1,3 +1,20 @@
+#
+# Copyright 2025 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+#
+
 org.springframework.cloud.gateway.server.mvc.filter.FilterSupplier=\
   org.springframework.cloud.gateway.server.mvc.filter.Bucket4jFilterFunctions.FilterSupplier,\
   org.springframework.cloud.gateway.server.mvc.filter.CircuitBreakerFilterFunctions.FilterSupplier,\
@@ -12,3 +29,6 @@ org.springframework.cloud.gateway.server.mvc.handler.HandlerSupplier=\
 org.springframework.cloud.gateway.server.mvc.predicate.PredicateSupplier=\
   org.springframework.cloud.gateway.server.mvc.predicate.MvcPredicateSupplier,\
   org.springframework.cloud.gateway.server.mvc.predicate.GatewayRequestPredicates.PredicateSupplier
+
+org.springframework.boot.env.EnvironmentPostProcessor=\
+  org.springframework.cloud.gateway.server.mvc.common.MultipartEnvironmentPostProcessor

spring-cloud-gateway-server-mvc/src/test/java/org/springframework/cloud/gateway/server/mvc/common/MultipartEnvironmentPostProcessorTests.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2013-2025 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+
+package org.springframework.cloud.gateway.server.mvc.common;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.mock.env.MockEnvironment;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.cloud.gateway.server.mvc.common.MultipartEnvironmentPostProcessor.MULTIPART_ENABLED_PROPERTY;
+import static org.springframework.cloud.gateway.server.mvc.common.MultipartEnvironmentPostProcessor.MULTIPART_PROPERTY_SOURCE_NAME;
+
+public class MultipartEnvironmentPostProcessorTests {
+
+	@Test
+	void multipartDisabledByDefault() {
+		MockEnvironment environment = new MockEnvironment();
+		MultipartEnvironmentPostProcessor processor = new MultipartEnvironmentPostProcessor();
+		processor.postProcessEnvironment(environment, null);
+
+		assertThat(environment.getPropertySources().contains(MULTIPART_PROPERTY_SOURCE_NAME)).isTrue();
+
+		Boolean multipartEnabled = environment.getProperty(MULTIPART_ENABLED_PROPERTY, Boolean.class);
+		assertThat(multipartEnabled).isFalse();
+	}
+
+	@Test
+	void multipartEnabledByUser() {
+		MockEnvironment environment = new MockEnvironment();
+		environment.setProperty(MULTIPART_ENABLED_PROPERTY, "true");
+		MultipartEnvironmentPostProcessor processor = new MultipartEnvironmentPostProcessor();
+		processor.postProcessEnvironment(environment, null);
+
+		assertThat(environment.getPropertySources().contains(MULTIPART_PROPERTY_SOURCE_NAME)).isFalse();
+
+		Boolean multipartEnabled = environment.getProperty(MULTIPART_ENABLED_PROPERTY, Boolean.class);
+		assertThat(multipartEnabled).isTrue();
+	}
+}