org.apache.openjpa.persistence.NoResultException

Problem
As we do search via primary key, it will show this exception message if JPA does not search any matched data

1:  org.apache.openjpa.persistence.NoResultException: The query on candidate type "class gov.fdc.nig.domain.Nigt020" with filter "select t1 from Nigt020 t1, Nigt022 t2 where t2.id.dlvUnit = ?1 and t2.id.taxCd = ?2 and t2.id.dlvYr = ?3 and t2.id.flgTp = ?4 and t2.id.serialNo = ?5 and t2.paraTp <> ?6 and t2.paraTp = t1.paraTp" was configured to have a unique result, but no instance matched the query.   
2:  at org.apache.openjpa.kernel.QueryImpl.singleResult(QueryImpl.java:1299) ~[com.ibm.ws.jpa.jar:1.0.1-SNAPSHOT]   
3:  at org.apache.openjpa.kernel.QueryImpl.toResult(QueryImpl.java:1221) ~[com.ibm.ws.jpa.jar:1.0.1-SNAPSHOT]   
4:  at org.apache.openjpa.kernel.QueryImpl.execute(QueryImpl.java:990) ~[com.ibm.ws.jpa.jar:1.0.1-SNAPSHOT]   
5:  at org.apache.openjpa.kernel.QueryImpl.execute(QueryImpl.java:805) ~[com.ibm.ws.jpa.jar:1.0.1-SNAPSHOT]   
6:  at org.apache.openjpa.kernel.QueryImpl.execute(QueryImpl.java:775) ~[com.ibm.ws.jpa.jar:1.0.1-SNAPSHOT]   
7:  at org.apache.openjpa.kernel.DelegatingQuery.execute(DelegatingQuery.java:533) ~[com.ibm.ws.jpa.jar:1.0.1-SNAPSHOT]   
8:  at org.apache.openjpa.persistence.QueryImpl.execute(QueryImpl.java:252) ~[com.ibm.ws.jpa.jar:1.0.1-SNAPSHOT]   
9:  at org.apache.openjpa.persistence.QueryImpl.getSingleResult(QueryImpl.java:317) ~[com.ibm.ws.jpa.jar:1.0.1-SNAPSHOT]   

The original approach is to call getSingleResult method:

1:  public Object createQueryForSingleResult(String jpql, Object[] params, Dao.PersistenceUnit persistenceUnitName) {   
2:       EntityManager em = getEntityManager(persistenceUnitName);   
3:       Query query = em.createQuery(jpql);   
4:       for (int i = 0; i < params.length; i++) {   
5:            query.setParameter(i + 1, params[i]);   
6:       }   
7:       return query.getSingleResult();   
8:  }  

Solution
Just change to this way, then the exception will not take place again:

1:  public Object createQueryForSingleResult(String jpql, Object[] params, Dao.PersistenceUnit persistenceUnitName) {   
2:       Object result = null;   
3:       EntityManager em = getEntityManager(persistenceUnitName);   
4:       Query query = em.createQuery(jpql);   
5:       for (int i = 0; i < params.length; i++) {   
6:            query.setParameter(i + 1, params[i]);   
7:       }   
8:       List list = query.getResultList();   
9:       if(!CollectionUtils.isEmpty(list)){   
10:            result = list.get(0);   
11:       }   
12:       return result;   
13:  }