Added more event and listener interface definitions.
diff --git a/net/api/src/main/java/org/onlab/onos/net/provider/AbstractProviderService.java b/net/api/src/main/java/org/onlab/onos/net/provider/AbstractProviderService.java
new file mode 100644
index 0000000..5497842
--- /dev/null
+++ b/net/api/src/main/java/org/onlab/onos/net/provider/AbstractProviderService.java
@@ -0,0 +1,46 @@
+package org.onlab.onos.net.provider;
+
+import static com.google.common.base.Preconditions.checkState;
+
+/**
+ * Base implementation of a provider service, which tracks the provider to
+ * which it is issued and can be invalidated.
+ *
+ * @param <P> type of the information provider
+ */
+public abstract class AbstractProviderService<P extends Provider> implements ProviderService<P> {
+
+ private boolean isValid = true;
+ private final P provider;
+
+ /**
+ * Creates a provider service on behalf of the specified provider.
+ *
+ * @param provider provider to which this service is being issued
+ */
+ protected AbstractProviderService(P provider) {
+ this.provider = provider;
+ }
+
+ /**
+ * Invalidates this provider service.
+ */
+ public void invalidate() {
+ isValid = false;
+ }
+
+ /**
+ * Checks the validity of this provider service.
+ *
+ * @throws java.lang.IllegalStateException if the service is no longer valid
+ */
+ public void checkValidity() {
+ checkState(isValid, "Provider service is no longer valid");
+ }
+
+ @Override
+ public P provider() {
+ return provider;
+ }
+
+}