Introduce ReadTransaction.exists()

[controller.git] / opendaylight / md-sal / sal-binding-api / src / main / java / org / opendaylight / controller / md / sal / binding / api / ReadTransaction.java

diff --git a/opendaylight/md-sal/sal-binding-api/src/main/java/org/opendaylight/controller/md/sal/binding/api/ReadTransaction.java b/opendaylight/md-sal/sal-binding-api/src/main/java/org/opendaylight/controller/md/sal/binding/api/ReadTransaction.java
index 21bcf23cd468a4f09570a6d8d4c40fb8699bfae2..01f525487a923d9b9fc59a5606be89b6ecaabb7f 100644 (file)
--- a/opendaylight/md-sal/sal-binding-api/src/main/java/org/opendaylight/controller/md/sal/binding/api/ReadTransaction.java
+++ b/opendaylight/md-sal/sal-binding-api/src/main/java/org/opendaylight/controller/md/sal/binding/api/ReadTransaction.java
@@ -9,6 +9,9 @@ package org.opendaylight.controller.md.sal.binding.api;
 
 import com.google.common.base.Optional;
 import com.google.common.util.concurrent.CheckedFuture;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.MoreExecutors;
+import org.opendaylight.controller.md.sal.common.api.MappingCheckedFuture;
 import org.opendaylight.controller.md.sal.common.api.data.AsyncReadTransaction;
 import org.opendaylight.controller.md.sal.common.api.data.LogicalDatastoreType;
 import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
@@ -45,6 +48,38 @@ public interface ReadTransaction extends AsyncReadTransaction<InstanceIdentifier
      *         {@link ReadFailedException} or an exception derived from ReadFailedException.</li>
      *         </ul>
      */
-    <T extends DataObject> CheckedFuture<Optional<T>,ReadFailedException> read(
+    <T extends DataObject> CheckedFuture<Optional<T>, ReadFailedException> read(
             LogicalDatastoreType store, InstanceIdentifier<T> path);
+
+    /**
+     * Checks if data is available in the logical data store located at provided path.
+     *
+     * <p>
+     * Note: a successful result from this method makes no guarantee that a subsequent call to {@link #read}
+     * will succeed. It is possible that the data resides in a data store on a remote node and, if that
+     * node goes down or a network failure occurs, a subsequent read would fail. Another scenario is if
+     * the data is deleted in between the calls to <code>exists</code> and <code>read</code>
+     *
+     * <p>
+     * Default implementation delegates to {@link #read(LogicalDatastoreType, InstanceIdentifier)}, implementations
+     * are advised to provide a more efficient override.
+     *
+     * @param store
+     *            Logical data store from which read should occur.
+     * @param path
+     *            Path which uniquely identifies subtree which client want to
+     *            check existence of
+     * @return a CheckFuture containing the result of the check.
+     *         <ul>
+     *         <li>If the data at the supplied path exists, the Future returns a Boolean
+     *         whose value is true, false otherwise</li>
+     *         <li>If checking for the data fails, the Future will fail with a
+     *         {@link ReadFailedException} or an exception derived from ReadFailedException.</li>
+     *         </ul>
+     */
+    default CheckedFuture<Boolean, ReadFailedException> exists(final LogicalDatastoreType store,
+            final InstanceIdentifier<?> path) {
+        return MappingCheckedFuture.create(Futures.transform(read(store, path), Optional::isPresent,
+            MoreExecutors.directExecutor()), ReadFailedException.MAPPER);
+    }
 }