java - org.datanucleus.store.query.QueryCompilerSyntaxException : Identifier expected at character 12 in "u.username== value"

Question

org.datanucleus.store.query.QueryCompilerSyntaxException: Identifier expected at character 12 in "u.username== value"

这是我尝试执行的查询:

try{
        Query q=em.createQuery("select u from UserJ u where u."+key+"== value");
        q.setParameter("value",value );
        return q.getResultList().isEmpty();
    }
    catch(PersistenceException x)
    {
        System.out.println(x.getLocalizedMessage());}
    finally{    
        em.close();
    }

key在哪里通过值传递:“用户名”

并且value通过值传递:"test"

Answer 1

您的语法不正确，请尝试以下查询:

Query q = em.createQuery("select u from UserJ u where u."+key+" = :value");