GUACAMOLE-926: Merge support for importing connections via CSV/JSON/YAML.

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/AtomicDirectoryOperation.java

@@ -0,0 +1,57 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.guacamole.net.auth;
+
+import org.apache.guacamole.GuacamoleException;
+
+/**
+ * An operation that should be attempted atomically when passed to
+ * {@link Directory#tryAtomically}, if atomic operations are supported by
+ * the Directory.
+ */
+public interface AtomicDirectoryOperation<ObjectType extends Identifiable>  {
+
+    /**
+     * Attempt the operation atomically. If the Directory does not support
+     * atomic operations, the atomic flag will be set to false. If the atomic
+     * flag is set to true, the provided directory is guaranteed to perform
+     * the operations within this function atomically. Atomicity of the
+     * provided directory outside this function, or of the directory invoking
+     * this function are not guaranteed.
+     *
+     * <p>NOTE: If atomicity is required for this operation, a 
+     * GuacamoleException may be thrown by this function before any changes are
+     * made, ensuring the operation will only ever be performed atomically.
+     *
+     * @param atomic
+     *     True if the provided directory is guaranteed to perform the operation
+     *     atomically within the context of this function.
+     *
+     * @param directory
+     *     A directory that will perform the operation atomically if the atomic
+     *     flag is set to true. If the flag is false, the directory may still
+     *     be used, though atomicity is not guaranteed.
+     *
+     * @throws GuacamoleException
+     *     If an issue occurs during the operation.
+     */
+    void executeOperation(boolean atomic, Directory<ObjectType> directory)
+            throws GuacamoleException;
+}

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/DelegatingDirectory.java

@@ -90,4 +90,10 @@ public class DelegatingDirectory<ObjectType extends Identifiable>
         directory.remove(identifier);
     }
 
+    @Override
+    public void tryAtomically(AtomicDirectoryOperation<ObjectType> operation)
+            throws GuacamoleException {
+        directory.tryAtomically(operation);
+    }
+
 }

guacamole-ext/src/main/java/org/apache/guacamole/net/auth/Directory.java

@@ -215,8 +215,29 @@ public interface Directory<ObjectType extends Identifiable> {
      * @param identifier The identifier of the object to remove.
      *
      * @throws GuacamoleException If an error occurs while removing the object,
-     *                            or if removing object is not allowed.
+     *                            or if removing the object is not allowed.
      */
     void remove(String identifier) throws GuacamoleException;
 
+    /**
+     * Attempt to perform the provided operation atomically if possible. If the
+     * operation can be performed atomically, the atomic flag will be set to
+     * true, and the directory passed to the provided operation callback will
+     * peform directory operations atomically within the operation callback.
+     *
+     * @param operation
+     *     The directory operation that should be performed atomically.
+     *
+     * @throws GuacamoleException
+     *     If an error occurs during execution of the provided operation.
+     */
+    default void tryAtomically(AtomicDirectoryOperation<ObjectType> operation)
+            throws GuacamoleException {
+
+        // By default, perform the operation non-atomically. If atomic operation
+        // is supported by an implementation, it must be implemented there.
+        operation.executeOperation(false, this);
+
+    }
+
 }