Allow plugins to get their canonical web URL injected

This change allows a plugin to get its canonical web URL injected at
runtime.

The URL is composed of the server's canonical web URL and the plugin's
name, i.e. `http://review.example.com:8080/plugins/plugin-name/`.

The canonical web URL may be injected into any .jar plugin regardless
of whether or not the plugin provides an HTTP servlet.

Change-Id: Id1a8489d49bfebff4ffdb8de58e9d0445113a09b

Documentation/dev-plugins.txt

@@ -191,6 +191,29 @@ public class MyClass {
 }
 ----
 
+A plugin can get its canonical web URL injected at runtime:
+
+[source,java]
+----
+public class MyClass {
+
+  private final String url;
+
+  @Inject
+  public MyClass(@PluginCanonicalWebUrl String url) {
+    this.url = url;
+  }
+
+  [...]
+}
+----
+
+The URL is composed of the server's canonical web URL and the plugin's
+name, i.e. `http://review.example.com:8080/plugin-name`.
+
+The canonical web URL may be injected into any .jar plugin regardless of
+whether or not the plugin provides an HTTP servlet.
+
 [[reload_method]]
 Reload Method
 ~~~~~~~~~~~~~

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/annotations/PluginCanonicalWebUrl.java

@@ -0,0 +1,42 @@
+// 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.gerrit.extensions.annotations;
+
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import com.google.inject.BindingAnnotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation applied to a String containing the plugin canonical web URL.
+ * <p>
+ * A plugin or extension may receive this string by Guice injection to discover
+ * the canonical web URL under which the plugin is available:
+ *
+ * <pre>
+ *  @Inject
+ *  MyType(@PluginCanonicalWebUrl String myUrl) {
+ *  ...
+ *  }
+ * </pre>
+ */
+@Target({ElementType.PARAMETER, ElementType.FIELD})
+@Retention(RUNTIME)
+@BindingAnnotation
+public @interface PluginCanonicalWebUrl {
+}

gerrit-server/src/main/java/com/google/gerrit/server/plugins/JarPlugin.java

@@ -17,6 +17,7 @@ package com.google.gerrit.server.plugins;
 import com.google.common.base.Strings;
 import com.google.common.collect.Lists;
 import com.google.gerrit.common.Nullable;
+import com.google.gerrit.extensions.annotations.PluginCanonicalWebUrl;
 import com.google.gerrit.extensions.annotations.PluginData;
 import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gerrit.extensions.registration.RegistrationHandle;
@@ -59,6 +60,7 @@ class JarPlugin extends Plugin {
   private final JarFile jarFile;
   private final Manifest manifest;
   private final File dataDir;
+  private final String pluginCanonicalWebUrl;
   private final ClassLoader classLoader;
   private Class<? extends Module> sysModule;
   private Class<? extends Module> sshModule;
@@ -71,6 +73,7 @@ class JarPlugin extends Plugin {
   private List<ReloadableRegistrationHandle<?>> reloadableHandles;
 
   public JarPlugin(String name,
+      String pluginCanonicalWebUrl,
       PluginUser pluginUser,
       File srcJar,
       FileSnapshot snapshot,
@@ -83,6 +86,7 @@ class JarPlugin extends Plugin {
       @Nullable Class<? extends Module> sshModule,
       @Nullable Class<? extends Module> httpModule) {
     super(name, srcJar, pluginUser, snapshot, apiType);
+    this.pluginCanonicalWebUrl = pluginCanonicalWebUrl;
     this.jarFile = jarFile;
     this.manifest = manifest;
     this.dataDir = dataDir;
@@ -193,6 +197,9 @@ class JarPlugin extends Plugin {
         bind(String.class)
           .annotatedWith(PluginName.class)
           .toInstance(getName());
+        bind(String.class)
+          .annotatedWith(PluginCanonicalWebUrl.class)
+          .toInstance(pluginCanonicalWebUrl);
 
         bind(File.class)
           .annotatedWith(PluginData.class)

gerrit-server/src/main/java/com/google/gerrit/server/plugins/PluginLoader.java

@@ -14,6 +14,7 @@
 
 package com.google.gerrit.server.plugins;
 
+import com.google.common.base.CharMatcher;
 import com.google.common.base.Joiner;
 import com.google.common.base.Objects;
 import com.google.common.base.Predicate;
@@ -30,6 +31,7 @@ import com.google.gerrit.extensions.events.LifecycleListener;
 import com.google.gerrit.extensions.systemstatus.ServerInformation;
 import com.google.gerrit.extensions.webui.JavaScriptPlugin;
 import com.google.gerrit.server.PluginUser;
+import com.google.gerrit.server.config.CanonicalWebUrl;
 import com.google.gerrit.server.config.ConfigUtil;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.SitePaths;
@@ -86,6 +88,7 @@ public class PluginLoader implements LifecycleListener {
   private final Queue<Plugin> toCleanup;
   private final Provider<PluginCleanerTask> cleaner;
   private final PluginScannerThread scanner;
+  private final Provider<String> urlProvider;
 
   @Inject
   public PluginLoader(SitePaths sitePaths,
@@ -93,7 +96,8 @@ public class PluginLoader implements LifecycleListener {
       ServerInformationImpl sii,
       PluginUser.Factory puf,
       Provider<PluginCleanerTask> pct,
-      @GerritServerConfig Config cfg) {
+      @GerritServerConfig Config cfg,
+      @CanonicalWebUrl Provider<String> provider) {
     pluginsDir = sitePaths.plugins_dir;
     dataDir = sitePaths.data_dir;
     tmpDir = sitePaths.tmp_dir;
@@ -106,6 +110,7 @@ public class PluginLoader implements LifecycleListener {
     toCleanup = Queues.newArrayDeque();
     cleanupHandles = Maps.newConcurrentMap();
     cleaner = pct;
+    urlProvider = provider;
 
     long checkFrequency = ConfigUtil.getTimeUnit(cfg,
         "plugins", null, "checkFrequency",
@@ -504,7 +509,13 @@ public class PluginLoader implements LifecycleListener {
       Class<? extends Module> sysModule = load(sysName, pluginLoader);
       Class<? extends Module> sshModule = load(sshName, pluginLoader);
       Class<? extends Module> httpModule = load(httpName, pluginLoader);
-      Plugin plugin = new JarPlugin(name, pluginUserFactory.create(name),
+
+      String url = String.format("%s/plugins/%s/",
+          CharMatcher.is('/').trimTrailingFrom(urlProvider.get()),
+          name);
+
+      Plugin plugin = new JarPlugin(name, url,
+          pluginUserFactory.create(name),
           srcJar, snapshot,
           jarFile, manifest,
           new File(dataDir, name), type, pluginLoader,