Disable resource cache when DevTools is enabled

Closes spring-projectsgh-3794
Closes spring-projectsgh-3739

Author: htynkn

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/env/DevToolsPropertyDefaultsPostProcessor.java

@@ -46,6 +46,7 @@ public class DevToolsPropertyDefaultsPostProcessor implements EnvironmentPostPro
 		properties.put("spring.mustache.cache", "false");
 		properties.put("server.session.persistent", "true");
 		properties.put("spring.h2.console.enabled", "true");
+		properties.put("spring.resources.cache-period", "0");
 		PROPERTIES = Collections.unmodifiableMap(properties);
 	}
 

spring-boot-devtools/src/test/java/org/springframework/boot/devtools/autoconfigure/LocalDevToolsAutoConfigurationTests.java

@@ -28,6 +28,7 @@
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.thymeleaf.ThymeleafAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.ResourceProperties;
 import org.springframework.boot.devtools.classpath.ClassPathChangedEvent;
 import org.springframework.boot.devtools.classpath.ClassPathFileSystemWatcher;
 import org.springframework.boot.devtools.filewatch.ChangedFiles;
@@ -89,6 +90,13 @@ public void thymeleafCacheIsFalse() throws Exception {
 		assertThat(resolver.isCacheable(), equalTo(false));
 	}
 
+	@Test
+	public void resourceCachePeriodIsZero() throws Exception {
+		this.context = initializeAndRun(WebResourcesConfig.class);
+		ResourceProperties properties = this.context.getBean(ResourceProperties.class);
+		assertThat(properties.getCachePeriod(), equalTo(0));
+	}
+
 	@Test
 	public void liveReloadServer() throws Exception {
 		this.context = initializeAndRun(Config.class);
@@ -242,4 +250,9 @@ public LiveReloadServer liveReloadServer() {
 
 	}
 
+	@Configuration
+	@Import({ LocalDevToolsAutoConfiguration.class, ResourceProperties.class })
+	public static class WebResourcesConfig {
+
+	}
 }