Relax ServletContext check for resource handling

This is a follow-up on commit 3b95e0b relaxing the expectation that a
ServletContext is present. Instead we check defensively and fall back
on PathExtensionContentNegotiationStrategy which can use JAF.

Issue: SPR-14577

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.java

@@ -22,7 +22,6 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
 import javax.servlet.ServletResponse;
 import javax.servlet.http.HttpServletRequest;
@@ -32,6 +31,7 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
 import org.springframework.beans.factory.InitializingBean;
+import org.springframework.beans.factory.SmartInitializingSingleton;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.support.ResourceRegion;
 import org.springframework.http.HttpHeaders;
@@ -91,7 +91,7 @@ import org.springframework.web.servlet.support.WebContentGenerator;
  * @since 3.0.4
  */
 public class ResourceHttpRequestHandler extends WebContentGenerator
-		implements HttpRequestHandler, InitializingBean, CorsConfigurationSource {
+		implements HttpRequestHandler, InitializingBean, SmartInitializingSingleton, CorsConfigurationSource {
 
 	// Servlet 3.1 setContentLengthLong(long) available?
 	private static final boolean contentLengthLongAvailable =
@@ -112,9 +112,7 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 
 	private ContentNegotiationManager contentNegotiationManager;
 
-	private ServletPathExtensionContentNegotiationStrategy pathExtensionStrategy;
-
-	private ServletContext servletContext;
+	private PathExtensionContentNegotiationStrategy pathExtensionStrategy;
 
 	private CorsConfiguration corsConfiguration;
 
@@ -248,11 +246,6 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 		return this.corsConfiguration;
 	}
 
-	@Override
-	protected void initServletContext(ServletContext servletContext) {
-		this.servletContext = servletContext;
-	}
-
 
 	@Override
 	public void afterPropertiesSet() throws Exception {
@@ -270,7 +263,6 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 		if (this.resourceRegionHttpMessageConverter == null) {
 			this.resourceRegionHttpMessageConverter = new ResourceRegionHttpMessageConverter();
 		}
-		this.pathExtensionStrategy = initPathExtensionStrategy();
 	}
 
 	/**
@@ -293,7 +285,12 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 		}
 	}
 
-	protected ServletPathExtensionContentNegotiationStrategy initPathExtensionStrategy() {
+	@Override
+	public void afterSingletonsInstantiated() {
+		this.pathExtensionStrategy = initContentNegotiationStrategy();
+	}
+
+	protected PathExtensionContentNegotiationStrategy initContentNegotiationStrategy() {
 		Map<String, MediaType> mediaTypes = null;
 		if (getContentNegotiationManager() != null) {
 			PathExtensionContentNegotiationStrategy strategy =
@@ -302,7 +299,9 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 				mediaTypes = new HashMap<>(strategy.getMediaTypes());
 			}
 		}
-		return new ServletPathExtensionContentNegotiationStrategy(this.servletContext, mediaTypes);
+		return (getServletContext() != null) ?
+			new ServletPathExtensionContentNegotiationStrategy(getServletContext(), mediaTypes) :
+			new PathExtensionContentNegotiationStrategy(mediaTypes);
 	}
 
 

spring-webmvc/src/test/java/org/springframework/web/servlet/config/annotation/ResourceHandlerRegistryTests.java

@@ -79,6 +79,8 @@ public class ResourceHandlerRegistryTests {
 		request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, "/testStylesheet.css");
 
 		ResourceHttpRequestHandler handler = getHandler("/resources/**");
+		handler.afterPropertiesSet();
+		handler.afterSingletonsInstantiated();
 		handler.handleRequest(request, this.response);
 
 		assertEquals("test stylesheet content", this.response.getContentAsString());

spring-webmvc/src/test/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandlerTests.java

@@ -81,6 +81,7 @@ public class ResourceHttpRequestHandlerTests {
 		this.handler.setCacheSeconds(3600);
 		this.handler.setServletContext(new TestServletContext());
 		this.handler.afterPropertiesSet();
+		this.handler.afterSingletonsInstantiated();
 
 		this.request = new MockHttpServletRequest("GET", "");
 		this.response = new MockHttpServletResponse();
@@ -147,6 +148,7 @@ public class ResourceHttpRequestHandlerTests {
 				.addFixedVersionStrategy("versionString", "/**");
 		this.handler.setResourceResolvers(Arrays.asList(versionResolver, new PathResourceResolver()));
 		this.handler.afterPropertiesSet();
+		this.handler.afterSingletonsInstantiated();
 
 		this.request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, "versionString/foo.css");
 		this.handler.handleRequest(this.request, this.response);
@@ -253,6 +255,7 @@ public class ResourceHttpRequestHandlerTests {
 		handler.setLocations(paths);
 		handler.setContentNegotiationManager(manager);
 		handler.afterPropertiesSet();
+		handler.afterSingletonsInstantiated();
 
 		this.request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, "foo.css");
 		handler.handleRequest(this.request, this.response);
@@ -274,6 +277,7 @@ public class ResourceHttpRequestHandlerTests {
 		handler.setLocations(paths);
 		handler.setContentNegotiationManager(manager);
 		handler.afterPropertiesSet();
+		handler.afterSingletonsInstantiated();
 
 		this.request.addHeader("Accept", "application/json,text/plain,*/*");
 		this.request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, "foo.html");
@@ -302,6 +306,7 @@ public class ResourceHttpRequestHandlerTests {
 		handler.setServletContext(servletContext);
 		handler.setLocations(paths);
 		handler.afterPropertiesSet();
+		handler.afterSingletonsInstantiated();
 
 		this.request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, "foo.css");
 		handler.handleRequest(this.request, this.response);
@@ -416,6 +421,7 @@ public class ResourceHttpRequestHandlerTests {
 		handler.setServletContext(new MockServletContext());
 		handler.setLocations(Arrays.asList(location1, location2));
 		handler.afterPropertiesSet();
+		handler.afterSingletonsInstantiated();
 
 		Resource[] locations = pathResolver.getAllowedLocations();
 		assertEquals(1, locations.length);