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;
import org.opendaylight.yangtools.yang.binding.DataObject;
import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
import com.google.common.base.Optional;
-import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.CheckedFuture;
+/**
+ * A transaction that provides read access to a logical data store.
+ * <p>
+ * For more information on usage and examples, please see the documentation in {@link AsyncReadTransaction}.
+ */
public interface ReadTransaction extends AsyncReadTransaction<InstanceIdentifier<?>, DataObject> {
- @Override
- ListenableFuture<Optional<DataObject>> read(LogicalDatastoreType store, InstanceIdentifier<?> path);
+
+ /**
+ * Reads data from the provided logical data store located at the provided path.
+ *<p>
+ * If the target is a subtree, then the whole subtree is read (and will be
+ * accessible from the returned data object).
+ *
+ * @param store
+ * Logical data store from which read should occur.
+ * @param path
+ * Path which uniquely identifies subtree which client want to
+ * read
+ * @return a CheckFuture containing the result of the read. The Future blocks until the
+ * commit operation is complete. Once complete:
+ * <ul>
+ * <li>If the data at the supplied path exists, the Future returns an Optional object
+ * containing the data.</li>
+ * <li>If the data at the supplied path does not exist, the Future returns
+ * Optional#absent().</li>
+ * <li>If the read of the data fails, the Future will fail with a
+ * {@link ReadFailedException} or an exception derived from ReadFailedException.</li>
+ * </ul>
+ */
+ <T extends DataObject> CheckedFuture<Optional<T>,ReadFailedException> read(
+ LogicalDatastoreType store, InstanceIdentifier<T> path);
}