added RestartServlet, which is able to trigger a complete restart of the context

scm-webapp/src/main/java/sonia/scm/ResteasyModule.java

@@ -0,0 +1,20 @@
+package sonia.scm;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.inject.servlet.ServletModule;
+import org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher;
+import org.jboss.resteasy.plugins.server.servlet.ResteasyContextParameters;
+
+import javax.inject.Singleton;
+import java.util.Map;
+
+public class ResteasyModule extends ServletModule {
+
+  @Override
+  protected void configureServlets() {
+    bind(HttpServletDispatcher.class).in(Singleton.class);
+
+    Map<String, String> initParams = ImmutableMap.of(ResteasyContextParameters.RESTEASY_SERVLET_MAPPING_PREFIX, "/api");
+    serve("/api/*").with(HttpServletDispatcher.class, initParams);
+  }
+}

scm-webapp/src/main/java/sonia/scm/ScmContextListener.java

@@ -126,6 +126,7 @@ public class ScmContextListener extends GuiceResteasyBootstrapServletContextList
     ClassOverrides overrides = ClassOverrides.findOverrides(pluginLoader.getUberClassLoader());
     List<Module> moduleList = Lists.newArrayList();
 
+    moduleList.add(new ResteasyModule());
     moduleList.add(new ScmInitializerModule());
     moduleList.add(new ScmEventBusModule());
     moduleList.add(new EagerSingletonModule());

scm-webapp/src/main/java/sonia/scm/boot/BootstrapContextFilter.java

@@ -34,22 +34,19 @@ package sonia.scm.boot;
 //~--- non-JDK imports --------------------------------------------------------
 
 import com.github.legman.Subscribe;
-
 import com.google.inject.servlet.GuiceFilter;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-
 import sonia.scm.SCMContext;
 import sonia.scm.Stage;
 import sonia.scm.event.ScmEventBus;
 
-//~--- JDK imports ------------------------------------------------------------
-
 import javax.servlet.FilterConfig;
 import javax.servlet.ServletContextEvent;
 import javax.servlet.ServletException;
 
+//~--- JDK imports ------------------------------------------------------------
+
 /**
  *
  * @author Sebastian Sdorra
@@ -65,6 +62,8 @@ public class BootstrapContextFilter extends GuiceFilter
 
   //~--- methods --------------------------------------------------------------
 
+  private final BootstrapContextListener listener = new BootstrapContextListener();
+
   /**
    * Restart the whole webapp context.
    *
@@ -85,29 +84,20 @@ public class BootstrapContextFilter extends GuiceFilter
     }
     else
     {
-
-      logger.warn(
-        "destroy filter pipeline, because of a received restart event");
+      logger.warn("destroy filter pipeline, because of a received restart event");
       destroy();
-      logger.warn(
-        "reinitialize filter pipeline, because of a received restart event");
-      super.init(filterConfig);
+
+      logger.warn("reinitialize filter pipeline, because of a received restart event");
+      initGuice();
     }
   }
 
-  /**
-   * Method description
-   *
-   *
-   * @param filterConfig
-   *
-   * @throws ServletException
-   */
   @Override
   public void init(FilterConfig filterConfig) throws ServletException
   {
     this.filterConfig = filterConfig;
-    super.init(filterConfig);
+
+    initGuice();
 
     if (SCMContext.getContext().getStage() == Stage.DEVELOPMENT)
     {
@@ -116,6 +106,19 @@ public class BootstrapContextFilter extends GuiceFilter
     }
   }
 
+  public void initGuice() throws ServletException {
+    super.init(filterConfig);
+
+    listener.contextInitialized(new ServletContextEvent(filterConfig.getServletContext()));
+  }
+
+  @Override
+  public void destroy() {
+    super.destroy();
+    listener.contextDestroyed(new ServletContextEvent(filterConfig.getServletContext()));
+    ServletContextCleaner.cleanup(filterConfig.getServletContext());
+  }
+
   //~--- fields ---------------------------------------------------------------
 
   /** Field description */

scm-webapp/src/main/java/sonia/scm/boot/BootstrapContextListener.java

@@ -187,40 +187,12 @@ public class BootstrapContextListener implements ServletContextListener
     return Boolean.getBoolean("sonia.scm.boot.disable-core-plugin-extraction");
   }
 
-  /**
-   * Restart the whole webapp context.
-   *
-   *
-   * @param event restart event
-   */
-  @Subscribe
-  public void handleRestartEvent(RestartEvent event)
-  {
-    logger.warn("received restart event from {} with reason: {}",
-      event.getCause(), event.getReason());
-
-    if (context == null)
-    {
-      logger.error("context is null, scm-manager is not initialized");
-    }
-    else
-    {
-      ServletContextEvent sce = new ServletContextEvent(context);
-
-      logger.warn("destroy context, because of a received restart event");
-      contextDestroyed(sce);
-      logger.warn("reinitialize context, because of a received restart event");
-      contextInitialized(sce);
-    }
-  }
-
   /**
    * Method description
    *
    *
    * @param context
    * @param pluginDirectory
-   * @param name
    * @param entry
    *
    * @throws IOException

scm-webapp/src/main/java/sonia/scm/boot/RestartServlet.java

@@ -0,0 +1,97 @@
+package sonia.scm.boot;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import sonia.scm.Priority;
+import sonia.scm.SCMContext;
+import sonia.scm.Stage;
+import sonia.scm.event.ScmEventBus;
+import sonia.scm.filter.WebElement;
+
+import javax.inject.Inject;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * This servlet sends a {@link RestartEvent} to the {@link ScmEventBus} which causes scm-manager to restart the context.
+ * The {@link RestartServlet} can be used for reloading java code or for installing plugins without a complete restart.
+ * At the moment the Servlet accepts only request, if scm-manager was started in the {@link Stage#DEVELOPMENT} stage.
+ *
+ * @since 2.0.0
+ */
+@Priority(0)
+@WebElement("/restart")
+public class RestartServlet extends HttpServlet {
+
+  private static final Logger LOG = LoggerFactory.getLogger(RestartServlet.class);
+
+  private final ObjectMapper objectMapper = new ObjectMapper();
+  private final AtomicBoolean restarting = new AtomicBoolean();
+
+  private final ScmEventBus eventBus;
+  private final Stage stage;
+
+  @Inject
+  public RestartServlet() {
+    this(ScmEventBus.getInstance(), SCMContext.getContext().getStage());
+  }
+
+  RestartServlet(ScmEventBus eventBus, Stage stage) {
+    this.eventBus = eventBus;
+    this.stage = stage;
+  }
+
+  @Override
+  protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
+    LOG.info("received sendRestartEvent request");
+
+    if (isRestartAllowed()) {
+
+      try (InputStream requestInput = req.getInputStream()) {
+        Reason reason = objectMapper.readValue(requestInput, Reason.class);
+        sendRestartEvent(resp, reason);
+      } catch (IOException ex) {
+        LOG.warn("failed to trigger sendRestartEvent event", ex);
+        resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
+      }
+
+    } else {
+      LOG.debug("received restart event in non development stage");
+      resp.setStatus(HttpServletResponse.SC_NOT_ACCEPTABLE);
+    }
+  }
+
+  private boolean isRestartAllowed() {
+    return stage == Stage.DEVELOPMENT;
+  }
+
+  private void sendRestartEvent(HttpServletResponse response, Reason reason) {
+    if ( restarting.compareAndSet(false, true) ) {
+      LOG.info("trigger sendRestartEvent, because of {}", reason.getMessage());
+      eventBus.post(new RestartEvent(RestartServlet.class, reason.getMessage()));
+
+      response.setStatus(HttpServletResponse.SC_ACCEPTED);
+    } else {
+      LOG.warn("scm-manager restarts already");
+      response.setStatus(HttpServletResponse.SC_CONFLICT);
+    }
+  }
+
+  public static class Reason {
+
+    private String message;
+
+    public void setMessage(String message) {
+      this.message = message;
+    }
+
+    public String getMessage() {
+      return message;
+    }
+  }
+}

scm-webapp/src/main/java/sonia/scm/boot/ServletContextCleaner.java

@@ -0,0 +1,59 @@
+package sonia.scm.boot;
+
+import com.google.common.collect.ImmutableSet;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.servlet.ServletContext;
+import java.util.Enumeration;
+import java.util.Set;
+
+/**
+ * Remove cached resources from {@link ServletContext} to allow a clean restart of scm-manager without stale or
+ * duplicated data.
+ *
+ * @since 2.0.0
+ */
+final class ServletContextCleaner {
+
+  private static final Logger LOG = LoggerFactory.getLogger(ServletContextCleaner.class);
+
+  private static final Set<String> REMOVE_PREFIX = ImmutableSet.of(
+    "org.jboss.resteasy",
+    "resteasy",
+    "org.apache.shiro",
+    "sonia.scm"
+  );
+
+  private ServletContextCleaner() {
+  }
+
+  /**
+   * Remove cached attributes from {@link ServletContext}.
+   *
+   * @param servletContext servlet context
+   */
+  static void cleanup(ServletContext servletContext) {
+    LOG.info("remove cached attributes from context");
+
+    Enumeration<String> attributeNames = servletContext.getAttributeNames();
+    while( attributeNames.hasMoreElements()) {
+      String name = attributeNames.nextElement();
+      if (shouldRemove(name)) {
+        LOG.info("remove attribute {} from servlet context", name);
+        servletContext.removeAttribute(name);
+      } else {
+        LOG.info("keep attribute {} in servlet context", name);
+      }
+    }
+  }
+
+  private static boolean shouldRemove(String name) {
+    for (String prefix : REMOVE_PREFIX) {
+      if (name.startsWith(prefix)) {
+        return true;
+      }
+    }
+    return false;
+  }
+}