Add support for custom ProtocolResolver with Devtools

Prior to this commit, custom `ProtocolResolvers` set on the
`ApplicationContext` were lost when Devtools is used as the customized
`ResourceLoader` did not copy any customization made to the default
resource loader.

This commit makes sure to copy any `ProtocolResolver` set on the context.

Closes gh-9331

Author: snicoll

spring-boot-devtools/src/main/java/org/springframework/boot/devtools/restart/ClassLoaderFilesResourcePatternResolver.java

@@ -22,6 +22,7 @@
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 import java.util.Map.Entry;
 
@@ -33,6 +34,7 @@
 import org.springframework.context.ApplicationContext;
 import org.springframework.core.io.AbstractResource;
 import org.springframework.core.io.DefaultResourceLoader;
+import org.springframework.core.io.ProtocolResolver;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.io.UrlResource;
@@ -52,6 +54,7 @@
  *
  * @author Andy Wilkinson
  * @author Phillip Webb
+ * @author Stephane Nicoll
  */
 final class ClassLoaderFilesResourcePatternResolver implements ResourcePatternResolver {
 
@@ -206,7 +209,20 @@ private static class ResourcePatternResolverFactory {
 		public ResourcePatternResolver getResourcePatternResolver(
 				ApplicationContext applicationContext, ResourceLoader resourceLoader) {
 			return new PathMatchingResourcePatternResolver(resourceLoader == null
-					? new DefaultResourceLoader() : resourceLoader);
+					? createResourceLoader(applicationContext) : resourceLoader);
+		}
+
+		private ResourceLoader createResourceLoader(
+				ApplicationContext applicationContext) {
+			DefaultResourceLoader resourceLoader = new DefaultResourceLoader();
+			if (applicationContext instanceof DefaultResourceLoader) {
+				Collection<ProtocolResolver> protocolResolvers =
+						((DefaultResourceLoader) applicationContext).getProtocolResolvers();
+				for (ProtocolResolver protocolResolver : protocolResolvers) {
+					resourceLoader.addProtocolResolver(protocolResolver);
+				}
+			}
+			return resourceLoader;
 		}
 
 	}
@@ -223,13 +239,26 @@ public ResourcePatternResolver getResourcePatternResolver(
 				ApplicationContext applicationContext, ResourceLoader resourceLoader) {
 			if (applicationContext instanceof WebApplicationContext) {
 				return new ServletContextResourcePatternResolver(resourceLoader == null
-						? new WebApplicationContextResourceLoader(
-								(WebApplicationContext) applicationContext)
+						? createResourceLoader((WebApplicationContext) applicationContext)
 						: resourceLoader);
 			}
 			return super.getResourcePatternResolver(applicationContext, resourceLoader);
 		}
 
+		private ResourceLoader createResourceLoader(
+				WebApplicationContext applicationContext) {
+			WebApplicationContextResourceLoader resourceLoader =
+					new WebApplicationContextResourceLoader(applicationContext);
+			if (applicationContext instanceof DefaultResourceLoader) {
+				Collection<ProtocolResolver> protocolResolvers =
+						((DefaultResourceLoader) applicationContext).getProtocolResolvers();
+				for (ProtocolResolver protocolResolver : protocolResolvers) {
+					resourceLoader.addProtocolResolver(protocolResolver);
+				}
+			}
+			return resourceLoader;
+		}
+
 	}
 
 	/**

spring-boot-devtools/src/test/java/org/springframework/boot/devtools/restart/ClassLoaderFilesResourcePatternResolverTests.java

@@ -30,6 +30,7 @@
 import org.springframework.boot.devtools.restart.classloader.ClassLoaderFiles;
 import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.ProtocolResolver;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.mock.web.MockServletContext;
@@ -38,6 +39,9 @@
 import org.springframework.web.context.support.ServletContextResource;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Matchers.any;
+import static org.mockito.Matchers.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
 
@@ -46,6 +50,7 @@
  *
  * @author Phillip Webb
  * @author Andy Wilkinson
+ * @author Stephane Nicoll
  */
 public class ClassLoaderFilesResourcePatternResolverTests {
 
@@ -125,6 +130,18 @@ public void customResourceLoaderIsUsedInNonWebApplication() throws Exception {
 		verify(resourceLoader).getResource("foo.txt");
 	}
 
+	@Test
+	public void customProtocolResolverIsUsedInNonWebApplication() throws Exception {
+		GenericApplicationContext context = new GenericApplicationContext();
+		Resource resource = mock(Resource.class);
+		ProtocolResolver resolver = mockProtocolResolver("foo:some-file.txt", resource);
+		context.addProtocolResolver(resolver);
+		this.resolver = new ClassLoaderFilesResourcePatternResolver(context, this.files);
+		Resource actual = this.resolver.getResource("foo:some-file.txt");
+		assertThat(actual).isSameAs(resource);
+		verify(resolver).resolve(eq("foo:some-file.txt"), any(ResourceLoader.class));
+	}
+
 	@Test
 	public void customResourceLoaderIsUsedInWebApplication() throws Exception {
 		GenericWebApplicationContext context = new GenericWebApplicationContext(
@@ -136,6 +153,26 @@ public void customResourceLoaderIsUsedInWebApplication() throws Exception {
 		verify(resourceLoader).getResource("foo.txt");
 	}
 
+	@Test
+	public void customProtocolResolverIsUsedInWebApplication() throws Exception {
+		GenericWebApplicationContext context = new GenericWebApplicationContext(
+				new MockServletContext());
+		Resource resource = mock(Resource.class);
+		ProtocolResolver resolver = mockProtocolResolver("foo:some-file.txt", resource);
+		context.addProtocolResolver(resolver);
+		this.resolver = new ClassLoaderFilesResourcePatternResolver(context, this.files);
+		Resource actual = this.resolver.getResource("foo:some-file.txt");
+		assertThat(actual).isSameAs(resource);
+		verify(resolver).resolve(eq("foo:some-file.txt"), any(ResourceLoader.class));
+	}
+
+	private ProtocolResolver mockProtocolResolver(String path, Resource resource) {
+		ProtocolResolver resolver = mock(ProtocolResolver.class);
+		given(resolver.resolve(eq(path), any(ResourceLoader.class)))
+				.willReturn(resource);
+		return resolver;
+	}
+
 	private File createFile(File folder, String name) throws IOException {
 		File file = new File(folder, name);
 		FileCopyUtils.copy("test".getBytes(), file);

spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc

@@ -853,6 +853,10 @@ NOTE: When deciding if an entry on the classpath should trigger a restart when i
 DevTools automatically ignores projects named `spring-boot`, `spring-boot-devtools`,
 `spring-boot-autoconfigure`, `spring-boot-actuator`, and `spring-boot-starter`.
 
+NOTE: DevTools needs to customize the `ResourceLoader` used by the `ApplicationContext`:
+if your application provides one already, it is going to be wrapped. Direct override of
+the `getResource` method on the `ApplicationContext` is not supported.
+
 [[using-spring-boot-restart-vs-reload]]
 .Restart vs Reload
 ****