SPR-7695 - Add ETag version of WebRequest.checkNotModified()

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

@@ -130,6 +130,10 @@ public class FacesWebRequest extends FacesRequestAttributes implements NativeWeb
 		return false;
 	}
 
+	public boolean checkNotModified(String eTag) {
+		return false;
+	}
+
 	public String getDescription(boolean includeClientInfo) {
 		ExternalContext externalContext = getExternalContext();
 		StringBuilder sb = new StringBuilder();

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

@@ -40,10 +40,16 @@ import org.springframework.util.StringUtils;
  */
 public class ServletWebRequest extends ServletRequestAttributes implements NativeWebRequest {
 
+	private static final String HEADER_ETAG = "ETag";
+
 	private static final String HEADER_IF_MODIFIED_SINCE = "If-Modified-Since";
 
+	private static final String HEADER_IF_NONE_MATCH = "If-None-Match";
+
 	private static final String HEADER_LAST_MODIFIED = "Last-Modified";
 
+	private static final String METHOD_GET = "GET";
+	
 
 	private HttpServletResponse response;
 
@@ -186,7 +192,7 @@ public class ServletWebRequest extends ServletRequestAttributes implements Nativ
 			long ifModifiedSince = getRequest().getDateHeader(HEADER_IF_MODIFIED_SINCE);
 			this.notModified = (ifModifiedSince >= (lastModifiedTimestamp / 1000 * 1000));
 			if (this.response != null) {
-				if (this.notModified && "GET".equals(getRequest().getMethod())) {
+				if (this.notModified && METHOD_GET.equals(getRequest().getMethod())) {
 					this.response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
 				}
 				else {
@@ -197,6 +203,30 @@ public class ServletWebRequest extends ServletRequestAttributes implements Nativ
 		return this.notModified;
 	}
 
+	public boolean checkNotModified(String eTag) {
+		if (StringUtils.hasLength(eTag) && !this.notModified &&
+				(this.response == null || !this.response.containsHeader(HEADER_ETAG))) {
+			if (!eTag.startsWith("\"")) {
+				eTag = "\"" + eTag;
+			}
+			if (!eTag.endsWith("\"")) {
+				eTag = eTag + "\"";
+			}
+			String ifNoneMatch = getRequest().getHeader(HEADER_IF_NONE_MATCH);
+			this.notModified = eTag.equals(ifNoneMatch);
+			if (this.response != null) {
+				if (this.notModified && METHOD_GET.equals(getRequest().getMethod())) {
+					this.response.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
+				}
+				else {
+					this.response.setHeader(HEADER_ETAG, eTag);
+				}
+			}
+		}
+		return this.notModified;
+
+	}
+
 	public boolean isNotModified() {
 		return this.notModified;
 	}

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

@@ -141,6 +141,9 @@ public interface WebRequest extends RequestAttributes {
 	 *   model.addAttribute(...);
 	 *   return "myViewName";
 	 * }</pre>
+	 * <p><strong>Note:</strong> that you typically want to use either
+	 * this {@link #checkNotModified(long)} method; or
+	 * {@link #checkNotModified(String)}, but not both.
 	 * @param lastModifiedTimestamp the last-modified timestamp that
 	 * the application determined for the underlying resource
 	 * @return whether the request qualifies as not modified,
@@ -149,6 +152,35 @@ public interface WebRequest extends RequestAttributes {
 	 */
 	boolean checkNotModified(long lastModifiedTimestamp);
 
+	/**
+	 * Check whether the request qualifies as not modified given the
+	 * supplied {@code ETag} (entity tag), as determined by the application.
+	 * <p>This will also transparently set the appropriate response headers,
+	 * for both the modified case and the not-modified case.
+	 * <p>Typical usage:
+	 * <pre class="code">
+	 * public String myHandleMethod(WebRequest webRequest, Model model) {
+	 *   String eTag = // application-specific calculation
+	 *   if (request.checkNotModified(eTag)) {
+	 *     // shortcut exit - no further processing necessary
+	 *     return null;
+	 *   }
+	 *   // further request processing, actually building content
+	 *   model.addAttribute(...);
+	 *   return "myViewName";
+	 * }</pre>
+	 * <p><strong>Note:</strong> that you typically want to use either
+	 * this {@link #checkNotModified(String)} method; or
+	 * {@link #checkNotModified(long)}, but not both.
+	 * @param eTag the entity tag that the application determined
+	 * for the underlying resource. This parameter will be padded
+	 * with quotes (") if necessary.   
+	 * @return whether the request qualifies as not modified,
+	 * allowing to abort request processing and relying on the response
+	 * telling the client that the content has not been modified
+	 */
+	boolean checkNotModified(String eTag);
+
 	/**
 	 * Get a short description of this request,
 	 * typically containing request URI and session id.