Add extension point to allow plugins to validate project creation

By implementing this extension point plugins can validate the creation
of new projects based on input arguments. E.g. a plugin could enforce
a certain name scheme for the project names. A more sophisticated
plugin could use this extension point to restrict the project creation
for certain groups to certain folders.

Change-Id: I6b5c69cd435acf9789111d13f31049ef38699215
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-server/src/main/java/com/google/gerrit/server/validators/ProjectCreationValidationListener.java

@@ -0,0 +1,35 @@
+// Copyright (C) 2014 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.server.validators;
+
+import com.google.gerrit.extensions.annotations.ExtensionPoint;
+import com.google.gerrit.server.project.CreateProjectArgs;
+
+/**
+ * Listener to provide validation on project creation.
+ */
+@ExtensionPoint
+public interface ProjectCreationValidationListener {
+  /**
+   * Project creation validation.
+   *
+   * Invoked by Gerrit just before a new project is going to be created.
+   *
+   * @param args arguments for the project creation
+   * @throws ValidationException if validation fails
+   */
+  public void validateNewProject(CreateProjectArgs args)
+      throws ValidationException;
+}

gerrit-server/src/main/java/com/google/gerrit/server/validators/ValidationException.java

@@ -0,0 +1,27 @@
+// Copyright (C) 2014 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.server.validators;
+
+public class ValidationException extends Exception {
+  private static final long serialVersionUID = 1L;
+
+  public ValidationException(String reason) {
+    super(reason);
+  }
+
+  public ValidationException(String reason, Throwable why) {
+    super(reason, why);
+  }
+}