Add 'DroolsRunnable' class

This provides a simple way to run arbitrary Java code within the
Drools thread. This change also includes a general way to specify
Drools rules that are automatically added to every Drools session.

Change-Id: I5ddcca4c807dc552fbcbd4a19dce311a4d358279
Issue-ID: POLICY-1948
Signed-off-by: Straubs, Ralph (rs8887) <rs8887@att.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/policy-core/src/main/resources/META-INF/drools/drl b/policy-core/src/main/resources/META-INF/drools/drl
new file mode 100644
index 00000000..949f235e
--- /dev/null
+++ b/policy-core/src/main/resources/META-INF/drools/drl
@@ -0,0 +1,40 @@
+/*
+ * ============LICENSE_START=======================================================
+ * policy-core
+ * ================================================================================
+ * Copyright (C) 2019 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.core;
+
+// This rule will match any 'DroolsRunnable' instance placed in Drools
+// memory, and run the 'DroolsRunnable.run()' method. It provides a way
+// to run arbitrary Java code within a Drools session thread by inserting
+// a 'DroolsRunnable' instance into Drools memory.
+
+rule "run-drools-runnable"
+    when
+        $runnable : DroolsRunnable()
+    then
+    {
+      // we retract it first, because the 'run()' method may traverse
+      // Drools objects
+      retract($runnable);
+
+      // run the code within the Drools thread
+      $runnable.run();
+    }
+end