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

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;
+  }
+}