How does hibernate implement lazy loading

Now, let's take a closer look at the following three examples. We'll also use SQLStatementCountValidator to understand the efficiency of the solution, by counting the number of queries executed. First of all, let's use lazy loading in the recommended way. So, we'll call our Transactional method in the service layer:. As we can see, this works and results in two roundtrips to the database. The first roundtrip selects users, and the second selects their documents.

Now, let's call a non-transactional method to simulate the error we get without a surrounding transaction:. As predicted, this results in an error as the getDocs function of User is used outside of a transaction. With the property turned on, we no longer get a LazyInitializationException. However, the count of the queries shows that six roundtrips have been made to the database. Here, one roundtrip selects users, and five roundtrips select documents for each of five users:.

With the property turned on, we don't have to worry about transactions and their boundaries. Hibernate manages that for us. It works perfectly for demos and when we don't care about performance issues. This may be ok if used to fetch a collection that contains only one element, or a single related object in a one to one relationship. Active Oldest Votes. Hibernate uses lazy loading by default. Improve this answer. Answer posted here, might help you also stackoverflow.

Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast The first ten years of our programming lives. GeneratedValue; import javax. GenerationType; import javax. Id; import javax. NamedQuery; import javax. OneToMany; import javax. HibernateDaoSupport; import com. ChildDAO; import com.

The fetch used here is a fetch keyword that initializes the collection of toys and returns the entity of the child that is qualified. Considering an online store, a common application used widely on the internet, maintains a product catalog. An entity can manage a series of other entities which can be products in this case. A catalog of such kind should be loaded from the huge database when a customer enters the application. Nobody would want to see the complete catalog so we need to implement lazy loading of hibernate to overcome such problems.

This is a guide to Lazy Loading in Hibernate.