JPA-Criteria Api-Objekte auswählen, wo die Spalte null ist

Ich habe eine Tabelle "Wort", das in PostgreSQL-DB:

CREATE TABLE word
(
   word_id bigserial NOT NULL,
   word character varying(15) NOT NULL,
   counter integer NOT NULL,
   base_letters character varying(15),
   CONSTRAINT word_pk PRIMARY KEY (word_id )
)

Und ich habe eine DAO-Methode was finden muss, um alle Wörter in der Tabelle, wo die Spalte 'base_letters'. Ich benutze den Frühling im Allgemeinen. Meine Methode:

    public List<Word> getAllWordsWithoutBaseLetters() {
        CriteriaQuery<Word> c = cb.createQuery(Word.class);
        Root<Word> words = c.from(Word.class); 
        c.select(words).where(cb.isNull(words.get("base_letters")));
        TypedQuery<Word> q = entityManager.createQuery(c);
        List<Word> allWordsWithoutBaseLetters = q.getResultList();
        return allWordsWithoutBaseLetters;
    }

Leider bin ich immer eine Fehlermeldung, die mich verwirrt:

ERROR [org.springframework.scheduling.support.MethodInvokingRunnable] - Invocation of method 'setBaseLettersToAllWordsWithoutThem' on target class [class $Proxy48] failed
java.lang.IllegalArgumentException: Unable to resolve attribute [base_letters] against path
    at org.hibernate.ejb.criteria.path.AbstractPathImpl.unknownAttribute(AbstractPathImpl.java:118)
    at org.hibernate.ejb.criteria.path.AbstractPathImpl.locateAttribute(AbstractPathImpl.java:223)
    at org.hibernate.ejb.criteria.path.AbstractPathImpl.get(AbstractPathImpl.java:194)
    at pl.net.grodek.snd.dao.WordDaoImpl.getAllWordsWithoutBaseLetters(WordDaoImpl.java:95)
    at pl.net.grodek.snd.service.WordServiceImpl.setBaseLettersToAllWordsWithoutThem(WordServiceImpl.java:175)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:309)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
    at $Proxy48.setBaseLettersToAllWordsWithoutThem(Unknown Source)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.util.MethodInvoker.invoke(MethodInvoker.java:273)
    at org.springframework.scheduling.support.MethodInvokingRunnable.run(MethodInvokingRunnable.java:65)
    at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:51)
    at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:81)
    at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
    at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
    at java.util.concurrent.FutureTask.run(Unknown Source)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(Unknown Source)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

Bitte erklären Sie mir, was falsch ist.

InformationsquelleAutor Mariusz Grodek | 2012-08-01