針對JPA的活動記錄模式：ActiveJPA

ActiveJPA基于JPA，提供了Martin Fowler所提出的活動記錄模式（Active Record pattern）的Java實現。借助于ActiveJPA，模型本身會作為DAO并與數據庫交互，這樣就不需要額外的代碼作為數據訪問層了。

ActiveJPA使用到了JPA規范，因此所有JPA的ORM實現（Hibernate、EclipseLink、OpenJPA等）都可以與ActiveJPA協同使用。

示例代碼：

// Get order by id
Order order = Order.findById(12345L);

// Get all orders for a customer that are shipped
List<Order> orders = Order.where("customer_email", "dummyemail@dummy.com", "status", "shipped");

// Get all orders for the product category 'books' and paginate it
Filter filter = new Filter();
filter.setPageNo(1);
filter.setPerPage(25);
filter.addCondition(new Condition("orderItems.product.category", Operator.eq, "books");
List<Order> orders = Order.where(filter);

// Count of orders matching the filter
Long count = Order.count(filter);

// Get the first order matching the filter
Long count = Order.first("customer_email", "dummyemail@dummy.com", "status", "shipped");

// Get the unique order matching the conditions
Long count = Order.one("customer_email", "dummyemail@dummy.com", "status", "shipped");

// Dump everything
List<Order> orders = Order.all();

// Delete all orders matching the filter
Long count = Order.deleteAll(filter);

// Check if order exists with the given identifier
boolean exists = Order.exists(1234L);

// Save order
order.setBillingAmount(1000.0);
order.persist();

// Delete order
order.delete();

// Update attributes
Map<String, Object> attributes = new HashMap<String, Object>();
attributes.put("billingAmount", 1000.0);
order.updateAttributes(attributes);

// Find order item by id within an order
order.collections("order_items").findById(123L);

// Search order items by filter with an order
order.collections("order_items").findById(filter);

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