Query q = em.createQuery("select p from Pais p");

 A signal was attempted before wait() on ConcurrencyManager. This normally means that an attempt was made to 
commit or rollback a transaction before it was started, or to rollback a transaction twice.

package br.com.germantech.cache;

import net.sf.ehcache.Cache;
import net.sf.ehcache.Element;

import org.eclipse.persistence.internal.sessions.AbstractRecord;
import org.eclipse.persistence.internal.sessions.AbstractSession;
import org.eclipse.persistence.queries.DatabaseQuery;
import org.eclipse.persistence.queries.QueryRedirector;
import org.eclipse.persistence.sessions.Record;
import org.eclipse.persistence.sessions.Session;

public class AggressiveCacheQueryRedirector implements QueryRedirector {

	private static final long serialVersionUID = -7875812708013000151L;

	public Object invokeQuery(DatabaseQuery query, Record arguments, Session session) {

        // Para evitar loop infinito
        query.setDoNotRedirect(true);

        // Cacheando todas as caches do tipo 'read-all'
//        if (query.isReadAllQuery()) {

            // Procura ou cria o cache de acordo com a classe
            EhCacheWrapper cacheWrapper = EhCacheWrapper.getInstance();
            Cache cache = cacheWrapper.findOrCreateCache(query.getDescriptor().getJavaClass());

            // Cria uma key para o cache e armazena
            CacheKey key = new CacheKey(query.getName(), arguments.values().toArray());
            Element element;

            // Retorna o resultado cacheado
            if ((element = cache.get(key)) != null) {
                return element.getValue();

            // Executa a query e armazena os resultados em cache
            } else {
                Object object = query.execute((AbstractSession)session, (AbstractRecord) arguments);
                if (object != null) {
                    cache.put(new Element(key, object));
                }
                return object;
            }
         // Executa a query sem passar pelo cache
//        } else {
//            return query.execute((AbstractSession)session, (AbstractRecord) arguments);
//        }
    }


}

Query q = em.createQuery("select m from Municipio m where m.estados_id = :est");
q.setParameter("est", estado);
		
redirectQueryToCache(q)