Hibernate中通过HQL/JPQL查询的方式实现动态数据获取

1. JPQL查询

Employee employee = entityManager.createQuery(    "select e " +    "from Employee e " +    "left join <strong>fetch</strong> e.projects " +    "where " +    "    e.username = :username and " +    "    e.password = :password",    Employee.class).setParameter( "username", username).setParameter( "password", password).getSingleResult();

2. Criteria查询

CriteriaBuilder builder = entityManager.getCriteriaBuilder();CriteriaQuery<Employee> query = builder.createQuery( Employee.class );Root<Employee> root = query.from( Employee.class );root.<strong>fetch</strong>( "projects", JoinType.LEFT);query.select(root).where(    builder.and(        builder.equal(root.get("username"), username),        builder.equal(root.get("password"), password)    ));Employee employee = entityManager.createQuery( query ).getSingleResult();

注意上述示例中黑体的“fetch"用法。