Add support for LiveReload without browser extensions

This commit improves Dev Tools live reload capabilities by adding
support for appending LiveReload.js script to rendered web pages.

See gh-32111

Signed-off-by: Vedran Pavic <vedran@vedranpavic.com>

Author: vpavic

spring-boot-project/spring-boot-devtools/build.gradle

@@ -47,6 +47,7 @@ dependencies {
 	optional("org.springframework:spring-jdbc")
 	optional("org.springframework:spring-orm")
 	optional("org.springframework:spring-web")
+	optional("org.springframework:spring-webmvc")
 	optional("org.springframework.security:spring-security-config")
 	optional("org.springframework.security:spring-security-web")
 	optional("org.springframework.data:spring-data-redis")

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/autoconfigure/LiveReloadServletConfiguration.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2012-2025 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.boot.devtools.autoconfigure;
+
+import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication.Type;
+import org.springframework.boot.devtools.livereload.LiveReloadScriptFilter;
+import org.springframework.boot.devtools.restart.RestartScope;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistration;
+import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+
+/**
+ * Servlet-specific local LiveReload configuration.
+ *
+ * @author Vedran Pavic
+ */
+@Configuration(proxyBeanMethods = false)
+@ConditionalOnWebApplication(type = Type.SERVLET)
+class LiveReloadServletConfiguration {
+
+	@Bean
+	@RestartScope
+	LiveReloadScriptFilter liveReloadScriptFilter(DevToolsProperties properties) {
+		return new LiveReloadScriptFilter(properties.getLivereload().getPort());
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	static class LiveReloadResourcesConfiguration implements WebMvcConfigurer {
+
+		@Override
+		public void addResourceHandlers(ResourceHandlerRegistry registry) {
+			ResourceHandlerRegistration registration = registry.addResourceHandler("/livereload.js");
+			registration.addResourceLocations("classpath:/org/springframework/boot/devtools/livereload/");
+		}
+
+	}
+
+}

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/autoconfigure/LocalDevToolsAutoConfiguration.java

@@ -44,6 +44,7 @@
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.Lazy;
 import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.context.event.GenericApplicationListener;
@@ -69,6 +70,7 @@ public class LocalDevToolsAutoConfiguration {
 	 */
 	@Configuration(proxyBeanMethods = false)
 	@ConditionalOnBooleanProperty(name = "spring.devtools.livereload.enabled", matchIfMissing = true)
+	@Import(LiveReloadServletConfiguration.class)
 	static class LiveReloadConfiguration {
 
 		@Bean

spring-boot-project/spring-boot-devtools/src/main/java/org/springframework/boot/devtools/livereload/LiveReloadScriptFilter.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2012-2025 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.boot.devtools.livereload;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+import jakarta.servlet.FilterChain;
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+
+import org.springframework.http.MediaType;
+import org.springframework.web.filter.OncePerRequestFilter;
+import org.springframework.web.util.ContentCachingResponseWrapper;
+
+/**
+ * A Servlet filter that appends LiveReload.js script to web pages.
+ *
+ * @author Vedran Pavic
+ * @since 3.5.0
+ */
+public class LiveReloadScriptFilter extends OncePerRequestFilter {
+
+	private final String scriptSnippet;
+
+	public LiveReloadScriptFilter(int liveReloadPort) {
+		this.scriptSnippet = String.format("<script src=\"/livereload.js?port=%d\"></script>", liveReloadPort);
+	}
+
+	@Override
+	protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
+			throws ServletException, IOException {
+		ContentCachingResponseWrapper responseToUse = new ContentCachingResponseWrapper(response);
+		filterChain.doFilter(request, responseToUse);
+		String contentType = responseToUse.getContentType();
+		if ((contentType != null) && MediaType.TEXT_HTML.isCompatibleWith(MediaType.parseMediaType(contentType))) {
+			String content = new String(responseToUse.getContentAsByteArray(), StandardCharsets.UTF_8);
+			String modifiedContent = content.replaceFirst("<head>", "<head>" + this.scriptSnippet);
+			response.setContentLength(modifiedContent.length());
+			response.getWriter().write(modifiedContent);
+		}
+		else {
+			responseToUse.copyBodyToResponse();
+		}
+	}
+
+}