自定義JPA CriteriaQuery的子句

Question

有沒有一種方法可以通過添加一些表達式來進一步限制聯接？ 用普通的SQL我寫：

SELECT c.*, COUNT(i.id) invoice_count
FROM customers c
LEFT JOIN invoices i ON i.customer_id = c.id
    AND i.creation_time >= '2012-01-01' -- <= extra restriction
    AND i.creation_time < '2013-01-01' -- <= extra restriction
GROUP BY c.id

我還沒有找到使用JPA 2.0 CriteriaQuery實施此方法的方法。

更新：根據要求，到目前為止，我的代碼（簡化）（沒有額外的限制）：

CriteriaQuery<CustomerAndInvoiceCount> criteriaQuery = criteriaBuilder.createQuery(CustomerAndInvoiceCount.class);

Root<Customer> customer = criteriaQuery.from(Customer.class);
ListJoin<Customer, Invoice> invoices = customer.join(Customer_.invoices, JoinType.LEFT);

criteriaQuery.select(criteriaBuilder.construct(
        CustomerAndInvoiceCount.class,
        customer,
        criteriaBuilder.count(invoices)));
criteriaQuery.groupBy(customer);

Answer 1

您應該只能夠添加條件謂詞，而不必擔心它們是否屬於ON子句或WHERE子句。