Entity manager tutorial: Updating and removing entries by using a query
You can update and remove entities by using a query.
Procedure
Update and remove entities by using a query.
Order.java
@Entity
public class Order
{
@Id String orderNumber;
@Index java.util.Date date;
@OneToOne(cascade=CascadeType.PERSIST) Customer customer;
@OneToMany(cascade=CascadeType.ALL, mappedBy="order")
@OrderBy("lineNumber") List<OrderLine> lines;
}
The order entity class is the same as it is in the previous example. The class still
provides the @Index annotation, because the query string uses the date to find the entity. The query
engine uses indices when they can be
used.public static void cancelOrdersUsingQuery(Session s) {
// Cancel all orders that were submitted 1 minute ago
java.util.Date cancelTime =
new java.util.Date(System.currentTimeMillis() - 60000);
EntityManager em = s.getEntityManager();
em.getTransaction().begin();
// Create a query that will find the order based on date. Since
// we have an index defined on the order date, the query
// will automatically use it.
Query query = em.createQuery("SELECT order FROM Order order
WHERE order.date >= ?1");
query.setParameter(1, cancelTime);
Iterator<Order> orderIterator = query.getResultIterator();
while(orderIterator.hasNext()) {
Order order = orderIterator.next();
// Verify that the order wasn't updated by someone else.
// Since the query used an index, there was no lock on the row.
if(order != null && order.date.getTime() >= cancelTime.getTime()) {
for(OrderLine line : order.lines) {
// Add the item back to the inventory.
line.item.quantityOnHand += line.quantity;
line.quantity = 0;
}
em.remove(order);
}
}
em.getTransaction().commit();
}
Like the previous example, the cancelOrdersUsingQuery method intends to cancel all
orders that were submitted in the past minute. To cancel the order, you find the order using a
query, add the items in the order back into the inventory, and remove the order and associated line
items from the system.