Key Pattern Filter

Question

Hi,
I use naming conventions for the keys, and would like to query based on a pattern in the key. e.g. all keys that start with "x"
I'm using Strings for my keys. How do I write a filter to do this?
I tried creating this Filter:
import java.util.regex.*;
public class KeyRegexFilter implements EntryFilter {
     protected Pattern pattern;
     public KeyRegexFilter(String regex) {
          pattern = Pattern.compile(regex);
     public boolean evaluateEntry(Map.Entry entry) {
          return evaluate(entry.getKey().toString());
     public boolean evaluate(Object obj) {
          if (obj instanceof ConverterCollections.ConverterMapEvent) {
               ConverterCollections.ConverterMapEvent mapEvent = (ConverterCollections.ConverterMapEvent)obj;
               return evaluate(mapEvent.getKey().toString());
          return false;
     protected boolean evaluate(String input) {
          Matcher matcher = pattern.matcher(input);
          return matcher.find();
The problem I ran into is that mapEvent.getKey() is a com.tangosol.util.Binary object.
Regards,
Harry

Answer 1

Hi Harry,
you could check the JavaDoc of the LikeFilter and the KeyExtractor classes.
E.g. your functionality of filtering for the cache key starting with x can be done with the following combination of those classes:
import com.tangosol.util.extractor.IdentityExtractor;
import com.tangosol.util.extractor.KeyExtractor;
import com.tangosol.util.filter.LikeFilter;
char chEscape='\\';
boolean bCaseSensitive=false;
ValueExtractor extractor = new KeyExtractor(IdentityExtractor.INSTANCE);
Filter filter = new LikeFilter(extractor, "x%", chEscape, bCaseSensitive);You can use the filter to query according to your requirements.
The extractor object can be used to create an index on your cache so that the querying proceeds even faster. You should create an ordered index for maximum performance for this query.
Best regards,
Robert