Add the plugin reload button to the plugin list page

src/main/scala/gitbucket/core/controller/SystemSettingsController.scala

@@ -181,9 +181,14 @@ trait SystemSettingsControllerBase extends AccountManagementControllerBase {
   })
 
   get("/admin/plugins")(adminOnly {
-    html.plugins(PluginRegistry().getPlugins())
+    html.plugins(PluginRegistry().getPlugins(), flash.get("info"))
   })
 
+  post("/admin/plugins/_reload")(adminOnly {
+    PluginRegistry.reload(request.getServletContext(), loadSystemSettings(), request2Session(request).conn)
+    flash += "info" -> "All plugins are reloaded."
+    redirect("/admin/plugins")
+  })
 
   get("/admin/users")(adminOnly {
     val includeRemoved = params.get("includeRemoved").map(_.toBoolean).getOrElse(false)

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

@@ -155,17 +155,26 @@ object PluginRegistry {
 
   private val logger = LoggerFactory.getLogger(classOf[PluginRegistry])
 
-  private val instance = new PluginRegistry()
+  private var instance = new PluginRegistry()
 
   /**
    * Returns the PluginRegistry singleton instance.
    */
   def apply(): PluginRegistry = instance
 
+  /**
+   * Reload all plugins.
+   */
+  def reload(context: ServletContext, settings: SystemSettings, conn: java.sql.Connection): Unit = synchronized {
+    shutdown(context, settings)
+    instance = new PluginRegistry()
+    initialize(context, settings, conn)
+  }
+
   /**
    * Initializes all installed plugins.
    */
-  def initialize(context: ServletContext, settings: SystemSettings, conn: java.sql.Connection): Unit = {
+  def initialize(context: ServletContext, settings: SystemSettings, conn: java.sql.Connection): Unit = synchronized {
     val pluginDir = new File(PluginHome)
     val manager = new JDBCVersionManager(conn)
 
@@ -207,7 +216,7 @@ object PluginRegistry {
     }
   }
 
-  def shutdown(context: ServletContext, settings: SystemSettings): Unit = {
+  def shutdown(context: ServletContext, settings: SystemSettings): Unit = synchronized {
     instance.getPlugins().foreach { pluginInfo =>
       try {
         pluginInfo.pluginClass.shutdown(instance, context, settings)
@@ -219,7 +228,6 @@ object PluginRegistry {
     }
   }
 
-
 }
 
 case class Link(id: String, label: String, path: String, icon: Option[String] = None)

src/main/scala/gitbucket/core/servlet/PluginControllerFilter.scala

@@ -7,10 +7,10 @@ import gitbucket.core.plugin.PluginRegistry
 
 class PluginControllerFilter extends Filter {
 
+  private var filterConfig: FilterConfig = null
+
   override def init(filterConfig: FilterConfig): Unit = {
-    PluginRegistry().getControllers().foreach { case (controller, _) =>
-      controller.init(filterConfig)
-    }
+    this.filterConfig = filterConfig
   }
 
   override def destroy(): Unit = {
@@ -26,6 +26,9 @@ class PluginControllerFilter extends Filter {
     }
 
     controller.map { case (controller, _) =>
+      if(controller.config == null){
+        controller.init(filterConfig)
+      }
       controller.doFilter(request, response, chain)
     }.getOrElse{
       chain.doFilter(request, response)

src/main/twirl/gitbucket/core/admin/plugins.scala.html

@@ -1,8 +1,11 @@
-@(plugins: List[gitbucket.core.plugin.PluginInfo])(implicit context: gitbucket.core.controller.Context)
+@(plugins: List[gitbucket.core.plugin.PluginInfo], info: Option[Any])(implicit context: gitbucket.core.controller.Context)
 @gitbucket.core.html.main("Plugins"){
   @gitbucket.core.admin.html.menu("plugins") {
+    @gitbucket.core.helper.html.information(info)
     <h1>Installed plugins</h1>
-
+    <form action="@context.path/admin/plugins/_reload" method="POST" class="pull-right">
+      <input type="submit" value="Reload plugins" class="btn btn-success">
+    </form>
     @if(plugins.size > 0) {
       <ul>
       @plugins.map { plugin =>