Using Predicate to search a keyset in Hazelcast

问题

I'm new to Hazelcast - evaluating and prototyping to see if it fits our distributed memory cache needs. One of the requirements was to be able to use wild cards to search for keys in a given map. Looking through the IMap documentation, looks like keySet(Predicate predicate) can be used. But I couldn't figure how to use the Predicate in such a way that given a wild card string, a keySet is returned containing all keys that match. An example will be helpful.

A snippet of my code. This is the client side.

IMap<String, String> mapTest1 = client.getMap("testMap");

mapTest1.put( "testKey1", "This is a Test" );
mapTest1.put( "testKey2", "This value has a long key name" );
mapTest1.put( "key3", "Another value" );
// Need a wild card search on the map, such that all keys with "%test%" will be returned.

Thanks.

回答1:

This should do the trick if I understood your request correctly:

public class Test {

    public static void main(String[] args) {
        HazelcastInstance hazelcastInstance = Hazelcast.newHazelcastInstance();

        IMap<String, String> map = hazelcastInstance.getMap("someMap");
        Collection<String> keys = map.keySet(
            new RegexPredicate("[a-z].*[a-z0-9]"));

        System.out.println(keys);
     }

     public static class RegexPredicate implements Predicate<String, String> {

        private String regex;
        private transient Pattern pattern;

        public RegexPredicate(String regex) {
            this.regex = regex;
        }

        @Override
        public boolean apply(Map.Entry<String, String> mapEntry) {
            if (pattern == null) {
                 pattern = Pattern.compile(regex);
            }
            Matcher matcher = pattern.matcher(mapEntry.getKey());
            return matcher.matches();
        }
    }
}

来源：https://stackoverflow.com/questions/28591381/using-predicate-to-search-a-keyset-in-hazelcast

标签

hazelcast