Provides declarative style plug-in definition.

src/main/scala/gitbucket/core/plugin/Plugin.scala

@@ -1,7 +1,9 @@
 package gitbucket.core.plugin
 
 import javax.servlet.ServletContext
+import gitbucket.core.controller.ControllerBase
 import gitbucket.core.service.SystemSettingsService.SystemSettings
+import gitbucket.core.util.ControlUtil._
 import gitbucket.core.util.Version
 
 /**
@@ -15,16 +17,51 @@ trait Plugin {
   val description: String
   val versions: Seq[Version]
 
+  /**
+   * Override to declare this plug-in provides images.
+   */
+  val images: Seq[(String, Array[Byte])] = Nil
+
+  /**
+   * Override to declare this plug-in provides controllers.
+   */
+  val controllers: Seq[(String, ControllerBase)] = Nil
+
+  /**
+   * Override to declare this plug-in provides JavaScript.
+   */
+  val javaScripts: Seq[(String, String)] = Nil
+
   /**
    * This method is invoked in initialization of plugin system.
    * Register plugin functionality to PluginRegistry.
    */
-  def initialize(registry: PluginRegistry, context: ServletContext, settings: SystemSettings): Unit
+  def initialize(registry: PluginRegistry, context: ServletContext, settings: SystemSettings): Unit = {
+    images.foreach { case (id, in) =>
+      registry.addImage(id, in)
+    }
+    controllers.foreach { case (path, controller) =>
+      registry.addController(path, controller)
+    }
+    javaScripts.foreach { case (path, script) =>
+      registry.addJavaScript(path, script)
+    }
+  }
 
   /**
    * This method is invoked in shutdown of plugin system.
    * If the plugin has any resources, release them in this method.
    */
-  def shutdown(registry: PluginRegistry, context: ServletContext, settings: SystemSettings): Unit
+  def shutdown(registry: PluginRegistry, context: ServletContext, settings: SystemSettings): Unit = {}
+
+  /**
+   * Helper method to get a resource from classpath.
+   */
+  protected def fromClassPath(path: String): Array[Byte] =
+    using(getClass.getClassLoader.getResourceAsStream(path)){ in =>
+      val bytes = new Array[Byte](in.available)
+      in.read(bytes)
+      bytes
+    }
 
 }

src/main/scala/gitbucket/core/plugin/PluginRegistory.scala

@@ -31,22 +31,32 @@ class PluginRegistry {
 
   def getPlugins(): List[PluginInfo] = plugins.toList
 
+  def addImage(id: String, bytes: Array[Byte]): Unit = {
+    val encoded = StringUtils.newStringUtf8(Base64.encodeBase64(bytes, false))
+    images += ((id, encoded))
+  }
+
+  @deprecated
   def addImage(id: String, in: InputStream): Unit = {
     val bytes = using(in){ in =>
       val bytes = new Array[Byte](in.available)
       in.read(bytes)
       bytes
     }
-    val encoded = StringUtils.newStringUtf8(Base64.encodeBase64(bytes, false))
-    images += ((id, encoded))
+    addImage(id, bytes)
   }
 
   def getImage(id: String): String = images(id)
 
-  def addController(controller: ControllerBase, path: String): Unit = {
+  def addController(path: String, controller: ControllerBase): Unit = {
     controllers += ((controller, path))
   }
 
+  @deprecated
+  def addController(controller: ControllerBase, path: String): Unit = {
+    addController(path, controller)
+  }
+
   def getControllers(): List[(ControllerBase, String)] = controllers.toList
 
   def addJavaScript(path: String, script: String): Unit = {