lazy =“ false”在休眠4.3.x中不起作用

Question

I am trying to test the functioning of lazy loading in hibernate with the following code.

        Query query = session.createQuery("From Publishers as publisher where publisher.publisherName <= :name");
    query.setString("name", "penguin");
    Publishers publisher = (Publishers)query.iterate().next();
     Set<Books> booksByPublisher  = new HashSet<>();
    booksByPublisher = publisher.getBooks();
    session.close();
    System.out.println(publisher.getPublisherName());
   for(Books book : booksByPublisher) {
        System.out.println(book);
    }

mapping for publishers and books classes are as following, respectively:

<class name="newapplication.domain.Publishers" table="PUBLISHERS" >
    <id name="publisherId" type="integer" column="PUBLISHER_ID"/>
    <property name="publisherName" type="string" column="PUBLISHER_NAME"/>
    <set name="books" table="BOOKS_PUBLISHERS" inverse="true" fetch="join" lazy="false">
        <key column="publisher"/>
        <many-to-many class="newapplication.domain.Books" column="book" />
    </set>
</class>



    <class name="newapplication.domain.Books" table="BOOKS" >
    <id name="bookId" type="integer" column="BOOK_ID">
        <generator class="sequence">
            <param name="sequence">BOOKIDSEQUENCE</param>
        </generator>
    </id>
    <property name="bookName" type="string" column="NAME"/>
    <many-to-one name="author" class="newapplication.domain.Authors" column="AUTHOR"/>
    <many-to-one name="cover" class="newapplication.domain.Covers" column="COVER"/>
    <set name="publishers" table="BOOKS_PUBLISHERS" lazy="false">
        <key column="BOOK"/>
        <many-to-many class="newapplication.domain.Publishers" column="PUBLISHER"/>

    </set>
</class>

Despite having set lazy="false" loading in the publisher class i get the following error.

Exception in thread "main" org.hibernate.LazyInitializationException: could not initialize proxy - no Session

What is wrong here? Shouldn't the Set be loaded as soon as the database is hit for the publishers' object?

Answer 1

Your many-to-one associations in Books are lazy; that's where the exception comes from.

By default, all associations are lazy when using Hibernate native mappings, as opposed to JPA standard (when using JPA-style mappings) where to-one associations are eager by default.