* Added JsonSerialize to the Flow-related containers.
* Implement the remaining toString() methods that were
  returning empty strings.
diff --git a/src/main/java/net/floodlightcontroller/util/serializers/FlowIdSerializer.java b/src/main/java/net/floodlightcontroller/util/serializers/FlowIdSerializer.java
new file mode 100644
index 0000000..0e69273
--- /dev/null
+++ b/src/main/java/net/floodlightcontroller/util/serializers/FlowIdSerializer.java
@@ -0,0 +1,23 @@
+package net.floodlightcontroller.util.serializers;
+
+import java.io.IOException;
+
+import org.codehaus.jackson.JsonGenerator;
+import org.codehaus.jackson.JsonProcessingException;
+import org.codehaus.jackson.map.JsonSerializer;
+import org.codehaus.jackson.map.SerializerProvider;
+
+import net.floodlightcontroller.util.FlowId;
+
+/**
+ * Serialize a Flow ID as a hexadecimal string.
+ */
+public class FlowIdSerializer extends JsonSerializer<FlowId> {
+
+    @Override
+    public void serialize(FlowId flowId, JsonGenerator jGen,
+			  SerializerProvider serializer)
+	throws IOException, JsonProcessingException {
+	jGen.writeString(flowId.toString());
+    }
+}