revised DispatcherServlet's last-modified handling to properly work with scoped controllers; added HEAD support to ResourceHttpRequestHandler

Author: jhoeller

org.springframework.web.servlet/src/main/java/org/springframework/web/servlet/DispatcherServlet.java

@@ -46,6 +46,7 @@
 import org.springframework.ui.context.ThemeSource;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
+import org.springframework.web.context.request.ServletWebRequest;
 import org.springframework.web.multipart.MultipartException;
 import org.springframework.web.multipart.MultipartHttpServletRequest;
 import org.springframework.web.multipart.MultipartResolver;
@@ -166,9 +167,6 @@ public class DispatcherServlet extends FrameworkServlet {
 	 */
 	public static final String VIEW_RESOLVER_BEAN_NAME = "viewResolver";
 
-	/** Request attribute to hold the currently chosen HandlerExecutionChain. Only used for internal optimizations. */
-	public static final String HANDLER_EXECUTION_CHAIN_ATTRIBUTE = DispatcherServlet.class.getName() + ".HANDLER";
-
 	/**
 	 * Request attribute to hold the current web application context. Otherwise only the global web app context is
 	 * obtainable by tags etc.
@@ -750,12 +748,29 @@ protected void doDispatch(HttpServletRequest request, HttpServletResponse respon
 				processedRequest = checkMultipart(request);
 
 				// Determine handler for the current request.
-				mappedHandler = getHandler(processedRequest, false);
+				mappedHandler = getHandler(processedRequest);
 				if (mappedHandler == null || mappedHandler.getHandler() == null) {
 					noHandlerFound(processedRequest, response);
 					return;
 				}
 
+				// Determine handler adapter for the current request.
+				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
+
+                // Process last-modified header, if supported by the handler.
+				String method = request.getMethod();
+				boolean isGet = "GET".equals(method);
+				if (isGet || "HEAD".equals(method)) {
+					long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
+					if (logger.isDebugEnabled()) {
+						String requestUri = urlPathHelper.getRequestUri(request);
+						logger.debug("Last-Modified value for [" + requestUri + "] is: " + lastModified);
+					}
+					if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
+						return;
+					}
+				}
+
 				// Apply preHandle methods of registered interceptors.
 				HandlerInterceptor[] interceptors = mappedHandler.getInterceptors();
 				if (interceptors != null) {
@@ -770,7 +785,6 @@ protected void doDispatch(HttpServletRequest request, HttpServletResponse respon
 				}
 
 				// Actually invoke the handler.
-				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
 				mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
 
 				// Do we need view name translation?
@@ -834,41 +848,6 @@ protected void doDispatch(HttpServletRequest request, HttpServletResponse respon
 		}
 	}
 
-	/**
-	 * Override HttpServlet's <code>getLastModified</code> method to evaluate the Last-Modified value
-	 * of the mapped handler.
-	 */
-	@Override
-	protected long getLastModified(HttpServletRequest request) {
-		if (logger.isDebugEnabled()) {
-			String requestUri = urlPathHelper.getRequestUri(request);
-			logger.debug(
-					"DispatcherServlet with name '" + getServletName() + "' determining Last-Modified value for [" +
-							requestUri + "]");
-		}
-		try {
-			HandlerExecutionChain mappedHandler = getHandler(request, true);
-			if (mappedHandler == null || mappedHandler.getHandler() == null) {
-				// Ignore -> will reappear on doService.
-				logger.debug("No handler found in getLastModified");
-				return -1;
-			}
-
-			HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
-			long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
-			if (logger.isDebugEnabled()) {
-				String requestUri = urlPathHelper.getRequestUri(request);
-				logger.debug("Last-Modified value for [" + requestUri + "] is: " + lastModified);
-			}
-			return lastModified;
-		}
-		catch (Exception ex) {
-			// Ignore -> will reappear on doService.
-			logger.debug("Exception thrown in getLastModified", ex);
-			return -1;
-		}
-	}
-
 	/**
 	 * Build a LocaleContext for the given request, exposing the request's primary locale as current locale.
 	 * <p>The default implementation uses the dispatcher's LocaleResolver to obtain the current locale,
@@ -882,7 +861,6 @@ protected LocaleContext buildLocaleContext(final HttpServletRequest request) {
 			public Locale getLocale() {
 				return localeResolver.resolveLocale(request);
 			}
-
 			@Override
 			public String toString() {
 				return getLocale().toString();
@@ -925,28 +903,16 @@ protected void cleanupMultipart(HttpServletRequest request) {
 	/**
 	 * Return the HandlerExecutionChain for this request. Try all handler mappings in order.
 	 * @param request current HTTP request
-	 * @param cache whether to cache the HandlerExecutionChain in a request attribute
 	 * @return the HandlerExceutionChain, or <code>null</code> if no handler could be found
 	 */
-	protected HandlerExecutionChain getHandler(HttpServletRequest request, boolean cache) throws Exception {
-		HandlerExecutionChain handler = (HandlerExecutionChain) request.getAttribute(HANDLER_EXECUTION_CHAIN_ATTRIBUTE);
-		if (handler != null) {
-			if (!cache) {
-				request.removeAttribute(HANDLER_EXECUTION_CHAIN_ATTRIBUTE);
-			}
-			return handler;
-		}
-
+	protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
 		for (HandlerMapping hm : this.handlerMappings) {
 			if (logger.isTraceEnabled()) {
 				logger.trace(
 						"Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
 			}
-			handler = hm.getHandler(request);
+			HandlerExecutionChain handler = hm.getHandler(request);
 			if (handler != null) {
-				if (cache) {
-					request.setAttribute(HANDLER_EXECUTION_CHAIN_ATTRIBUTE, handler);
-				}
 				return handler;
 			}
 		}

org.springframework.web.servlet/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.java

@@ -28,30 +28,33 @@
 import org.springframework.util.FileCopyUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.web.HttpRequestHandler;
+import org.springframework.web.context.request.ServletWebRequest;
 import org.springframework.web.servlet.HandlerMapping;
 import org.springframework.web.servlet.support.WebContentGenerator;
 
 /**
  * {@link HttpRequestHandler} that serves static resources optimized for superior browser performance 
- * (according to the guidelines of Page Speed, YSlow, etc.) by adding far future cache expiration headers.
+ * (according to the guidelines of Page Speed, YSlow, etc.) by allowing for flexible cache settings
+ * ({@link #setCacheSeconds "cacheSeconds" property}, last-modified support).
  *
- * <p>The constructor takes a list of Spring {@link Resource} locations from which static resources are allowed 
- * to be served by this handler. For a given request, the list of locations will be consulted in order for the
- * presence of the requested resource, and the first found match will be written to the response, with {@code 
- * Expires} and {@code Cache-Control} headers set for one year in the future. The handler also properly evaluates
- * the {@code Last-Modified} header (if present) so that a {@code 304} status code will be returned as appropriate, 
- * avoiding unnecessary overhead for resources that are already cached by the client. The use of {@code Resource}
- * locations allows resource requests to easily be mapped to locations other than the web application root. For
+ * <p>The {@link #setLocations "locations" property takes a list of Spring {@link Resource} locations
+ * from which static resources are allowed  to be served by this handler. For a given request, the
+ * list of locations will be consulted in order for the presence of the requested resource, and the
+ * first found match will be written to the response, with {@code Expires} and {@code Cache-Control}
+ * headers set as configured. The handler also properly evaluates the {@code Last-Modified} header
+ * (if present) so that a {@code 304} status code will be returned as appropriate, avoiding unnecessary
+ * overhead for resources that are already cached by the client. The use of {@code Resource} locations
+ * allows resource requests to easily be mapped to locations other than the web application root. For
  * example, resources could be served from a classpath location such as "classpath:/META-INF/public-web-resources/", 
  * allowing convenient packaging and serving of resources such as a JavaScript library from within jar files.
  *
- * <p>To ensure that users with a primed browser cache get the latest changes to application-specific resources 
- * upon deployment of new versions of the application, it is recommended that a version string is used in the URL 
- * mapping pattern that selects this handler.  Such patterns can be easily parameterized using Spring EL. See the
- * reference manual for further examples of this approach.  
+ * <p>To ensure that users with a primed browser cache get the latest changes to application-specific
+ * resources upon deployment of new versions of the application, it is recommended that a version string
+ * is used in the URL  mapping pattern that selects this handler. Such patterns can be easily parameterized
+ * using Spring EL. See the reference manual for further examples of this approach.
  *
- * <p>Rather than being directly configured as a bean, this handler will typically be configured through use of 
- * the <code>&lt;mvc:resources/&gt;</code> Spring configuration tag. 
+ * <p>Rather than being directly configured as a bean, this handler will typically be configured
+ * through use of the <code>&lt;mvc:resources/&gt;</code> XML configuration element.
  *
  * @author Keith Donald
  * @author Jeremy Grelle
@@ -64,7 +67,7 @@ public class ResourceHttpRequestHandler extends WebContentGenerator implements H
 
 
 	public ResourceHttpRequestHandler() {
-		super(METHOD_GET);
+		super(METHOD_GET, METHOD_HEAD);
 	}
 
 	/**
@@ -98,13 +101,15 @@ public void handleRequest(HttpServletRequest request, HttpServletResponse respon
 			response.sendError(HttpServletResponse.SC_NOT_FOUND);
 			return;
 		}
-		if (checkNotModified(resource, request, response)) {
+		setHeaders(resource, response);
+		if (new ServletWebRequest(request, response).checkNotModified(resource.lastModified()) ||
+				METHOD_HEAD.equals(request.getMethod())) {
 			return;
 		}
-		writeResponse(resource, response);
+		writeContent(resource, response);
 	}
 
-	private Resource getResource(HttpServletRequest request) {
+	protected Resource getResource(HttpServletRequest request) {
 		String path = (String) request.getAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE);
 		if (path == null) {
 			throw new IllegalStateException("Required request attribute '" +
@@ -128,22 +133,7 @@ private Resource getResource(HttpServletRequest request) {
 		return null;
 	}
 
-	private boolean checkNotModified(Resource resource,HttpServletRequest request, HttpServletResponse response)
-			throws IOException {
-
-		long ifModifiedSince = request.getDateHeader("If-Modified-Since");
-		long lastModified = resource.lastModified();
-		boolean notModified = ifModifiedSince >= (lastModified / 1000 * 1000);
-		if (notModified) {
-			response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
-		}
-		else {
-			response.setDateHeader("Last-Modified", lastModified);
-		}
-		return notModified;
-	}
-
-	private void writeResponse(Resource resource, HttpServletResponse response) throws IOException {
+	protected void setHeaders(Resource resource, HttpServletResponse response) throws IOException {
 		MediaType mediaType = getMediaType(resource);
 		if (mediaType != null) {
 			response.setContentType(mediaType.toString());
@@ -153,12 +143,15 @@ private void writeResponse(Resource resource, HttpServletResponse response) thro
 			throw new IOException("Resource content too long (beyond Integer.MAX_VALUE): " + resource);
 		}
 		response.setContentLength((int) length);
-		FileCopyUtils.copy(resource.getInputStream(), response.getOutputStream());
 	}
 
 	protected MediaType getMediaType(Resource resource) {
 		String mimeType = getServletContext().getMimeType(resource.getFilename());
 		return (StringUtils.hasText(mimeType) ? MediaType.parseMediaType(mimeType) : null);
 	}
 
+	protected void writeContent(Resource resource, HttpServletResponse response) throws IOException {
+		FileCopyUtils.copy(resource.getInputStream(), response.getOutputStream());
+	}
+
 }

org.springframework.web/src/main/java/org/springframework/web/context/request/ServletWebRequest.java

@@ -186,7 +186,7 @@ public boolean checkNotModified(long lastModifiedTimestamp) {
 			long ifModifiedSince = getRequest().getDateHeader(HEADER_IF_MODIFIED_SINCE);
 			this.notModified = (ifModifiedSince >= (lastModifiedTimestamp / 1000 * 1000));
 			if (this.response != null) {
-				if (this.notModified) {
+				if (this.notModified && "GET".equals(getRequest().getMethod())) {
 					this.response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
 				}
 				else {

org.springframework.web/src/main/java/org/springframework/web/context/request/WebRequest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2008 the original author or authors.
+ * Copyright 2002-2010 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.
@@ -35,6 +35,7 @@ public interface WebRequest extends RequestAttributes {
 	/**
 	 * Return the request header of the given name, or <code>null</code> if none.
 	 * <p>Retrieves the first header value in case of a multi-value header.
+	 * @since 3.0
 	 * @see javax.servlet.http.HttpServletRequest#getHeader(String)
 	 */
 	String getHeader(String headerName);
@@ -43,14 +44,15 @@ public interface WebRequest extends RequestAttributes {
 	 * Return the request header values for the given header name,
 	 * or <code>null</code> if none.
 	 * <p>A single-value header will be exposed as an array with a single element.
+	 * @since 3.0
 	 * @see javax.servlet.http.HttpServletRequest#getHeaders(String)
 	 */
 	String[] getHeaderValues(String headerName);
 
 	/**
 	 * Return a Iterator over request header names.
-	 * @see javax.servlet.http.HttpServletRequest#getHeaderNames()
 	 * @since 3.0
+	 * @see javax.servlet.http.HttpServletRequest#getHeaderNames()
 	 */
 	Iterator<String> getHeaderNames();