HBASE-6794 FilterBase should provide a default implementation of toByteArray

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1386842 13f79535-47bb-0310-9956-ffa450edef68

hbase-server/src/main/java/org/apache/hadoop/hbase/filter/FilterBase.java

@@ -150,6 +150,13 @@ public abstract class FilterBase extends Filter {
     return this.getClass().getSimpleName();
   }
 
+  /**
+   * Return length 0 byte array for Filters that don't require special serialization
+   */
+  public byte [] toByteArray() {
+    return new byte[0];
+  }
+
   /**
    * Default implementation so that writers of custom filters aren't forced to implement.
    *