Fix for issue #45000 - ServletRegistrationBean has those properties, but @ServletRegistration hasn't: initParameters, servletRegistrationBeans, multipartConfig

Author: dmytrodanilenkov

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/ServletContextInitializerBeans.java

@@ -321,10 +321,53 @@ private void configureFromAnnotation(ServletRegistrationBean<Servlet> bean, Serv
 			if (registration.urlMappings().length > 0) {
 				bean.setUrlMappings(Arrays.asList(registration.urlMappings()));
 			}
+
+			if (registration.initParameters().length > 0) {
+				bean.setInitParameters(parseInitParameters(registration.initParameters()));
+			}
+
+			ServletRegistration.MultipartConfigValues multipart = registration.multipartConfig();
+			boolean isMultipartConfigUsed = !(multipart.location().isEmpty()
+					&& multipart.maxFileSize() == -1L
+					&& multipart.maxRequestSize() == -1L
+					&& multipart.fileSizeThreshold() == 0);
+			if (isMultipartConfigUsed) {
+				bean.setMultipartConfig(new MultipartConfigElement(
+						multipart.location(),
+						multipart.maxFileSize(),
+						multipart.maxRequestSize(),
+						multipart.fileSizeThreshold()
+				));
+			}
+
+			for (Class<? extends ServletRegistrationBean<?>> beanClass : registration.servletRegistrationBeans()) {
+				ServletRegistrationBean<?> extraBean = this.beanFactory.getBean(beanClass);
+				bean.getInitParameters().putAll(extraBean.getInitParameters());
+			}
+
+		}
+
+		private Map<String, String> parseInitParameters(String[] initParamsArray) {
+			Map<String, String> initParams = new LinkedHashMap<>();
+			for (String kv : initParamsArray) {
+				int index = kv.indexOf('=');
+				if (index != -1) {
+					String key = kv.substring(0, index).trim();
+					String value = kv.substring(index + 1).trim();
+					initParams.put(key, value);
+				}
+				else {
+					throw new IllegalArgumentException(
+							"initParameters must be in 'key=value' format, got: " + kv);
+				}
+			}
+			return initParams;
 		}
 
 	}
 
+
+
 	/**
 	 * {@link RegistrationBeanAdapter} for {@link Filter} beans.
 	 */

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/servlet/ServletRegistration.java

@@ -23,6 +23,8 @@
 import java.lang.annotation.Target;
 
 import jakarta.servlet.Servlet;
+import jakarta.servlet.annotation.MultipartConfig;
+import jakarta.servlet.annotation.WebInitParam;
 
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.AliasFor;
@@ -87,4 +89,35 @@
 	 */
 	int loadOnStartup() default -1;
 
+	/**
+	 * Init parameters to set on the servlet, as {@code "key=value"} pairs.
+	 */
+	String[] initParameters() default {};
+
+	/**
+	 * (Optional) Additional servlet-registration beans to apply.
+	 * Usually left empty unless you need custom bean logic.
+	 */
+	Class<? extends ServletRegistrationBean<?>>[] servletRegistrationBeans() default {};
+
+	/**
+	 * Multi-part configuration. Mirrors {@link jakarta.servlet.annotation.MultipartConfig}.
+	 * If you omit it (no fields changed), it will not set a multipart config.
+	 */
+	MultipartConfigValues multipartConfig() default @MultipartConfigValues;
+
+	/**
+	 * Nested annotation that parallels the fields of {@link jakarta.servlet.annotation.MultipartConfig}.
+	 */
+	@Target({})
+	@Retention(RetentionPolicy.RUNTIME)
+	@Documented
+	@interface MultipartConfigValues {
+
+		String location() default "";
+		long maxFileSize() default -1L;
+		long maxRequestSize() default -1L;
+		int fileSizeThreshold() default 0;
+
+	}
 }

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/servlet/ServletContextInitializerBeansTests.java

@@ -179,6 +179,73 @@ void shouldApplyOrderFromOrderAttribute() {
 					.isEqualTo(ServletConfigurationWithAnnotationAndOrder.ORDER));
 	}
 
+	@Test
+	@SuppressWarnings("unchecked")
+	void shouldApplyExtendedServletRegistrationAnnotation() {
+		load(ServletConfigurationWithExtendedAttributes.class);
+		// Grab all initializers in the context, including beans that are adapted from @ServletRegistration
+		ServletContextInitializerBeans initializerBeans = new ServletContextInitializerBeans(
+				this.context.getBeanFactory(), TestServletContextInitializer.class);
+
+		// We expect two registrations in this config: 'testServletWithInitParametersAndMultipart'
+		// and 'testServletWithExtraBean'. So let's filter them individually or pick the one we want to assert.
+
+		// 1) Check the one with initParameters + multipartConfig
+		ServletRegistrationBean<?> bean = findServletRegistrationBeanByName(initializerBeans, "extended");
+		assertThat(bean).as("extended servlet registration bean").isNotNull();
+
+		// Verify that the standard attributes were applied
+		assertThat(bean.getServletName()).isEqualTo("extended");
+		assertThat(bean.getUrlMappings()).containsExactly("/extended/*");
+
+		// Verify our new initParameters
+		assertThat(bean.getInitParameters()).containsEntry("hello", "world")
+				.containsEntry("flag", "true");
+
+		// Verify multi-part config
+		assertThat(bean.getMultipartConfig()).isNotNull();
+		assertThat(bean.getMultipartConfig().getLocation()).isEqualTo("/tmp");
+		assertThat(bean.getMultipartConfig().getMaxFileSize()).isEqualTo(1024);
+		assertThat(bean.getMultipartConfig().getMaxRequestSize()).isEqualTo(4096);
+		assertThat(bean.getMultipartConfig().getFileSizeThreshold()).isEqualTo(128);
+	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	void shouldApplyServletRegistrationAnnotationWithExtraRegistrationBeans() {
+		load(ServletConfigurationWithExtendedAttributes.class);
+		ServletContextInitializerBeans initializerBeans = new ServletContextInitializerBeans(
+				this.context.getBeanFactory(), TestServletContextInitializer.class);
+
+		// 2) Check the one referencing 'servletRegistrationBeans'
+		ServletRegistrationBean<?> bean = findServletRegistrationBeanByName(initializerBeans, "extendedWithExtraBeans");
+		assertThat(bean).as("extendedWithExtraBeans registration bean").isNotNull();
+
+		// Confirm standard attributes
+		assertThat(bean.getServletName()).isEqualTo("extendedWithExtraBeans");
+		assertThat(bean.getUrlMappings()).containsExactly("/extra/*");
+
+		// Confirm that the extra init param from MyExtraServletRegistrationBean was merged
+		assertThat(bean.getInitParameters()).containsEntry("extra", "fromExtraBean");
+	}
+
+	/**
+	 * Simple helper method to locate a specific ServletRegistrationBean by its name
+	 * from the given ServletContextInitializerBeans collection.
+	 */
+	@SuppressWarnings("rawtypes")
+	private ServletRegistrationBean findServletRegistrationBeanByName(
+			ServletContextInitializerBeans initializerBeans, String servletName) {
+
+		return initializerBeans.stream()
+				.filter(ServletRegistrationBean.class::isInstance)
+				.map(ServletRegistrationBean.class::cast)
+				.filter((registrationBean) -> servletName.equals(registrationBean.getServletName()))
+				.findFirst()
+				.orElse(null);
+	}
+
+
 	private void load(Class<?>... configuration) {
 		this.context = new AnnotationConfigApplicationContext(configuration);
 	}
@@ -385,4 +452,50 @@ public void onStartup(ServletContext servletContext) {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class ServletConfigurationWithExtendedAttributes {
+
+		@Bean
+		@ServletRegistration(
+				name = "extended",
+				urlMappings = "/extended/*",
+				initParameters = { "hello=world", "flag=true" },
+				multipartConfig = @ServletRegistration.MultipartConfigValues(
+						location = "/tmp",
+						maxFileSize = 1024,
+						maxRequestSize = 4096,
+						fileSizeThreshold = 128
+				)
+		)
+		TestServlet testServletWithInitParametersAndMultipart() {
+			return new TestServlet();
+		}
+
+		@Bean
+		MyExtraServletRegistrationBean myExtraServletRegistrationBean() {
+			MyExtraServletRegistrationBean bean = new MyExtraServletRegistrationBean();
+			bean.addInitParameter("extra", "fromExtraBean");
+			return bean;
+		}
+
+		@Bean
+		@ServletRegistration(
+				name = "extendedWithExtraBeans",
+				urlMappings = "/extra/*",
+				servletRegistrationBeans = { MyExtraServletRegistrationBean.class }
+		)
+		TestServlet testServletWithExtraBean() {
+			return new TestServlet();
+		}
+
+		static class MyExtraServletRegistrationBean extends ServletRegistrationBean<HttpServlet> {
+
+			MyExtraServletRegistrationBean() {
+				super();
+			}
+
+		}
+	}
+
+
 }