Add api-resource-locks feature

Added ResourceLockFeatureAPI, to provide an interface for PolicyGuard
to use to access other locking mechanisms.
Move lock API to policy-core.
Changed the interface and added Callback support.  Added a class to
invoke the API implementers.
Changed to set a future instead of expecting the callback to implement
the future interface. Also refactored, creating "lock" sub-package.
Add junit tests.
Increase junit coverage.
IsLocked & isLockedBy should check all arguments.
Make ImplFuture protected instead of public.
Simplify locking - move callback support to an optional feature.
Move Reference class to policy-utils.
Return plain Future instead of LockRequestFuture.

Change-Id: I65154d33833914b4332e02d1ef2512f4c5f09b16
Issue-ID: POLICY-577
Signed-off-by: Jim Hahn <jrh3@att.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/policy-utils/src/main/java/org/onap/policy/drools/utils/Reference.java b/policy-utils/src/main/java/org/onap/policy/drools/utils/Reference.java
new file mode 100644
index 00000000..0c4155fe
--- /dev/null
+++ b/policy-utils/src/main/java/org/onap/policy/drools/utils/Reference.java
@@ -0,0 +1,72 @@
+/*
+ * ============LICENSE_START=======================================================
+ * ONAP
+ * ================================================================================
+ * Copyright (C) 2018 AT&T Intellectual Property. All rights reserved.
+ * ================================================================================
+ * 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.
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.drools.utils;
+
+/**
+ * Reference to an object. Used within functional methods, where thread-safety is not
+ * required.
+ * 
+ * @param <T> type of object contained within the reference
+ */
+public class Reference<T> {
+    private T value;
+
+    /**
+     * 
+     * @param value
+     */
+    public Reference(T value) {
+        this.value = value;
+    }
+
+    /**
+     * @return the current value
+     */
+    public final T get() {
+        return value;
+    }
+
+    /**
+     * Sets the reference to point to a new value.
+     * 
+     * @param newValue
+     */
+    public final void set(T newValue) {
+        this.value = newValue;
+    }
+
+    /**
+     * Sets the value to a new value, if the value is currently the same as the old value.
+     * 
+     * @param oldValue
+     * @param newValue
+     * @return {@code true} if the value was updated, {@code false} otherwise
+     */
+    public boolean compareAndSet(T oldValue, T newValue) {
+        if (value == oldValue) {
+            value = newValue;
+            return true;
+
+        } else {
+            return false;
+        }
+    }
+}