Subtree merge in gwtexpui as gerrit-gwtexpui

Nobody uses the standalone gwtexpui project that we know of. Its
release process is frustrating, as even getting a simple bugfix into
Gerrit requires releasing gwtexpui (incrementing the version, tagging,
deploying, setting the next snapshot version).

Change-Id: I958ed659b8de8d855f7f9a7f4df66f6b4aad882f

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/server/CacheControlFilter.java

@@ -0,0 +1,106 @@
+// Copyright (C) 2008 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gwtexpui.server;
+
+import java.io.IOException;
+import java.util.concurrent.TimeUnit;
+
+import javax.servlet.Filter;
+import javax.servlet.FilterChain;
+import javax.servlet.FilterConfig;
+import javax.servlet.ServletException;
+import javax.servlet.ServletRequest;
+import javax.servlet.ServletResponse;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/**
+ * Forces GWT resources to cache for a very long time.
+ * <p>
+ * GWT compiled JavaScript and ImageBundles can be cached indefinitely by a
+ * browser and/or an edge proxy, as they never contain user-specific data and
+ * are named by a unique checksum. If their content is ever modified then the
+ * URL changes, so user agents would request a different resource. We force
+ * these resources to have very long expiration times.
+ * <p>
+ * To use, add the following block to your <code>web.xml</code>:
+ *
+ * <pre>
+ * &lt;filter&gt;
+ *     &lt;filter-name&gt;CacheControl&lt;/filter-name&gt;
+ *     &lt;filter-class&gt;com.google.gwtexpui.server.CacheControlFilter&lt;/filter-class&gt;
+ *   &lt;/filter&gt;
+ *   &lt;filter-mapping&gt;
+ *     &lt;filter-name&gt;CacheControl&lt;/filter-name&gt;
+ *     &lt;url-pattern&gt;/*&lt;/url-pattern&gt;
+ *   &lt;/filter-mapping&gt;
+ * </pre>
+ */
+public class CacheControlFilter implements Filter {
+  public void init(final FilterConfig config) {
+  }
+
+  public void destroy() {
+  }
+
+  public void doFilter(final ServletRequest sreq, final ServletResponse srsp,
+      final FilterChain chain) throws IOException, ServletException {
+    final HttpServletRequest req = (HttpServletRequest) sreq;
+    final HttpServletResponse rsp = (HttpServletResponse) srsp;
+    final String pathInfo = pathInfo(req);
+
+    if (cacheForever(pathInfo, req)) {
+      CacheHeaders.setCacheable(req, rsp, 365, TimeUnit.DAYS);
+    } else if (nocache(pathInfo)) {
+      CacheHeaders.setNotCacheable(rsp);
+    }
+
+    chain.doFilter(req, rsp);
+  }
+
+  private static boolean cacheForever(final String pathInfo,
+      final HttpServletRequest req) {
+    if (pathInfo.endsWith(".cache.html")) {
+      return true;
+    } else if (pathInfo.endsWith(".cache.gif")) {
+      return true;
+    } else if (pathInfo.endsWith(".cache.png")) {
+      return true;
+    } else if (pathInfo.endsWith(".cache.css")) {
+      return true;
+    } else if (pathInfo.endsWith(".cache.jar")) {
+      return true;
+    } else if (pathInfo.endsWith(".cache.swf")) {
+      return true;
+    } else if (pathInfo.endsWith(".nocache.js")) {
+      final String v = req.getParameter("content");
+      return v != null && v.length() > 20;
+    }
+    return false;
+  }
+
+  private static boolean nocache(final String pathInfo) {
+    if (pathInfo.endsWith(".nocache.js")) {
+      return true;
+    }
+    return false;
+  }
+
+  private static String pathInfo(final HttpServletRequest req) {
+    final String uri = req.getRequestURI();
+    final String ctx = req.getContextPath();
+    return uri.startsWith(ctx) ? uri.substring(ctx.length()) : uri;
+  }
+}

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/server/CacheHeaders.java

@@ -0,0 +1,118 @@
+// Copyright (C) 2013 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gwtexpui.server;
+
+import static java.util.concurrent.TimeUnit.DAYS;
+import static java.util.concurrent.TimeUnit.SECONDS;
+
+import java.util.concurrent.TimeUnit;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+/** Utilities to manage HTTP caching directives in responses. */
+public class CacheHeaders {
+  private static final long MAX_CACHE_DURATION = DAYS.toSeconds(365);
+
+  /**
+   * Do not cache the response, anywhere.
+   *
+   * @param res response being returned.
+   */
+  public static void setNotCacheable(HttpServletResponse res) {
+    String cc = "no-cache, no-store, max-age=0, must-revalidate";
+    res.setHeader("Cache-Control", cc);
+    res.setHeader("Pragma", "no-cache");
+    res.setHeader("Expires", "Fri, 01 Jan 1990 00:00:00 GMT");
+    res.setDateHeader("Date", System.currentTimeMillis());
+  }
+
+  /**
+   * Permit caching the response for up to the age specified.
+   * <p>
+   * If the request is on a secure connection (e.g. SSL) private caching is
+   * used. This allows the user-agent to cache the response, but requests
+   * intermediate proxies to not cache. This may offer better protection for
+   * Set-Cookie headers.
+   * <p>
+   * If the request is on plaintext (insecure), public caching is used. This may
+   * allow an intermediate proxy to cache the response, including any Set-Cookie
+   * header that may have also been included.
+   *
+   * @param req current request.
+   * @param res response being returned.
+   * @param age how long the response can be cached.
+   * @param unit time unit for age, usually {@link TimeUnit#SECONDS}.
+   */
+  public static void setCacheable(
+      HttpServletRequest req, HttpServletResponse res,
+      long age, TimeUnit unit) {
+    if (req.isSecure()) {
+      setCacheablePrivate(res, age, unit);
+    } else {
+      setCacheablePublic(res, age, unit);
+    }
+  }
+
+  /**
+   * Allow the response to be cached by proxies and user-agents.
+   * <p>
+   * If the response includes a Set-Cookie header the cookie may be cached by a
+   * proxy and returned to multiple browsers behind the same proxy. This is
+   * insecure for authenticated connections.
+   *
+   * @param res response being returned.
+   * @param age how long the response can be cached.
+   * @param unit time unit for age, usually {@link TimeUnit#SECONDS}.
+   */
+  public static void setCacheablePublic(HttpServletResponse res,
+      long age, TimeUnit unit) {
+    long now = System.currentTimeMillis();
+    long sec = maxAgeSeconds(age, unit);
+
+    res.setDateHeader("Expires", now + SECONDS.toMillis(sec));
+    res.setDateHeader("Date", now);
+    cache(res, "public", age, unit);
+  }
+
+  /**
+   * Allow the response to be cached only by the user-agent.
+   *
+   * @param res response being returned.
+   * @param age how long the response can be cached.
+   * @param unit time unit for age, usually {@link TimeUnit#SECONDS}.
+   */
+  public static void setCacheablePrivate(HttpServletResponse res,
+      long age, TimeUnit unit) {
+    long now = System.currentTimeMillis();
+    res.setDateHeader("Expires", now);
+    res.setDateHeader("Date", now);
+    cache(res, "private", age, unit);
+  }
+
+  private static void cache(HttpServletResponse res,
+      String type, long age, TimeUnit unit) {
+    res.setHeader("Cache-Control", String.format(
+        "%s, max-age=%d",
+        type, maxAgeSeconds(age, unit)));
+  }
+
+  private static long maxAgeSeconds(long age, TimeUnit unit) {
+    return Math.min(unit.toSeconds(age), MAX_CACHE_DURATION);
+  }
+
+  private CacheHeaders() {
+  }
+}