Hibernate.org Community Documentation

- Prev
- Next

## Chapter 25. Example: Weblog Application

## 25.1. Persistent Classes

The persistent classes here represent a weblog and an item posted in a weblog. They are to be modelled as a standard parent/child relationship, but we will use an ordered bag, instead of a set:

    package eg;

    import java.util.List;

    public class Blog {
        private Long _id;
        private String _name;
        private List _items;

        public Long getId() {
            return _id;
        }
        public List getItems() {
            return _items;
        }
        public String getName() {
            return _name;
        }
        public void setId(Long long1) {
            _id = long1;
        }
        public void setItems(List list) {
            _items = list;
        }
        public void setName(String string) {
            _name = string;
        }
    }

    package eg;

    import java.text.DateFormat;
    import java.util.Calendar;

    public class BlogItem {
        private Long _id;
        private Calendar _datetime;
        private String _text;
        private String _title;
        private Blog _blog;

        public Blog getBlog() {
            return _blog;
        }
        public Calendar getDatetime() {
            return _datetime;
        }
        public Long getId() {
            return _id;
        }
        public String getText() {
            return _text;
        }
        public String getTitle() {
            return _title;
        }
        public void setBlog(Blog blog) {
            _blog = blog;
        }
        public void setDatetime(Calendar calendar) {
            _datetime = calendar;
        }
        public void setId(Long long1) {
            _id = long1;
        }
        public void setText(String string) {
            _text = string;
        }
        public void setTitle(String string) {
            _title = string;
        }
    }

## 25.2. Hibernate Mappings

The XML mappings are now straightforward. For example:

    <?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

    <hibernate-mapping package="eg">

        <class
            name="Blog"
            table="BLOGS">

            <id
                name="id"
                column="BLOG_ID">

                <generator class="native"/>

            </id>

            <property
                name="name"
                column="NAME"
                not-null="true"
                unique="true"/>

            <bag
                name="items"
                inverse="true"
                order-by="DATE_TIME"
                cascade="all">

                <key column="BLOG_ID"/>
                <one-to-many class="BlogItem"/>

            </bag>

        </class>

    </hibernate-mapping>

    <?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

    <hibernate-mapping package="eg">

        <class
            name="BlogItem"
            table="BLOG_ITEMS"
            dynamic-update="true">

            <id
                name="id"
                column="BLOG_ITEM_ID">

                <generator class="native"/>

            </id>

            <property
                name="title"
                column="TITLE"
                not-null="true"/>

            <property
                name="text"
                column="TEXT"
                not-null="true"/>

            <property
                name="datetime"
                column="DATE_TIME"
                not-null="true"/>

            <many-to-one
                name="blog"
                column="BLOG_ID"
                not-null="true"/>

        </class>

    </hibernate-mapping>

## 25.3. Hibernate Code

The following class demonstrates some of the kinds of things we can do with these classes using Hibernate:

    package eg;

    import java.util.ArrayList;
    import java.util.Calendar;
    import java.util.Iterator;
    import java.util.List;

    import org.hibernate.HibernateException;
    import org.hibernate.Query;
    import org.hibernate.Session;
    import org.hibernate.SessionFactory;
    import org.hibernate.Transaction;
    import org.hibernate.cfg.Configuration;
    import org.hibernate.tool.hbm2ddl.SchemaExport;

    public class BlogMain {

        private SessionFactory _sessions;

        public void configure() throws HibernateException {
            _sessions = new Configuration()
                .addClass(Blog.class)
                .addClass(BlogItem.class)
                .buildSessionFactory();
        }

        public void exportTables() throws HibernateException {
            Configuration cfg = new Configuration()
                .addClass(Blog.class)
                .addClass(BlogItem.class);
            new SchemaExport(cfg).create(true, true);
        }

        public Blog createBlog(String name) throws HibernateException {

            Blog blog = new Blog();
            blog.setName(name);
            blog.setItems( new ArrayList() );

            Session session = _sessions.openSession();
            Transaction tx = null;
            try {
                tx = session.beginTransaction();
                session.persist(blog);
                tx.commit();
            }
            catch (HibernateException he) {
                if (tx!=null) tx.rollback();
                throw he;
            }
            finally {
                session.close();
            }
            return blog;
        }

        public BlogItem createBlogItem(Blog blog, String title, String text)
                            throws HibernateException {

            BlogItem item = new BlogItem();
            item.setTitle(title);
            item.setText(text);
            item.setBlog(blog);
            item.setDatetime( Calendar.getInstance() );
            blog.getItems().add(item);

            Session session = _sessions.openSession();
            Transaction tx = null;
            try {
                tx = session.beginTransaction();
                session.update(blog);
                tx.commit();
            }
            catch (HibernateException he) {
                if (tx!=null) tx.rollback();
                throw he;
            }
            finally {
                session.close();
            }
            return item;
        }

        public BlogItem createBlogItem(Long blogid, String title, String text)
                            throws HibernateException {

            BlogItem item = new BlogItem();
            item.setTitle(title);
            item.setText(text);
            item.setDatetime( Calendar.getInstance() );

            Session session = _sessions.openSession();
            Transaction tx = null;
            try {
                tx = session.beginTransaction();
                Blog blog = (Blog) session.load(Blog.class, blogid);
                item.setBlog(blog);
                blog.getItems().add(item);
                tx.commit();
            }
            catch (HibernateException he) {
                if (tx!=null) tx.rollback();
                throw he;
            }
            finally {
                session.close();
            }
            return item;
        }

        public void updateBlogItem(BlogItem item, String text)
                        throws HibernateException {

            item.setText(text);

            Session session = _sessions.openSession();
            Transaction tx = null;
            try {
                tx = session.beginTransaction();
                session.update(item);
                tx.commit();
            }
            catch (HibernateException he) {
                if (tx!=null) tx.rollback();
                throw he;
            }
            finally {
                session.close();
            }
        }

        public void updateBlogItem(Long itemid, String text)
                        throws HibernateException {

            Session session = _sessions.openSession();
            Transaction tx = null;
            try {
                tx = session.beginTransaction();
                BlogItem item = (BlogItem) session.load(BlogItem.class, itemid);
                item.setText(text);
                tx.commit();
            }
            catch (HibernateException he) {
                if (tx!=null) tx.rollback();
                throw he;
            }
            finally {
                session.close();
            }
        }

        public List listAllBlogNamesAndItemCounts(int max)
                        throws HibernateException {

            Session session = _sessions.openSession();
            Transaction tx = null;
            List result = null;
            try {
                tx = session.beginTransaction();
                Query q = session.createQuery(
                    "select blog.id, blog.name, count(blogItem) " +
                    "from Blog as blog " +
                    "left outer join blog.items as blogItem " +
                    "group by blog.name, blog.id " +
                    "order by max(blogItem.datetime)"
                );
                q.setMaxResults(max);
                result = q.list();
                tx.commit();
            }
            catch (HibernateException he) {
                if (tx!=null) tx.rollback();
                throw he;
            }
            finally {
                session.close();
            }
            return result;
        }

        public Blog getBlogAndAllItems(Long blogid)
                        throws HibernateException {

            Session session = _sessions.openSession();
            Transaction tx = null;
            Blog blog = null;
            try {
                tx = session.beginTransaction();
                Query q = session.createQuery(
                    "from Blog as blog " +
                    "left outer join fetch blog.items " +
                    "where blog.id = :blogid"
                );
                q.setParameter("blogid", blogid);
                blog  = (Blog) q.uniqueResult();
                tx.commit();
            }
            catch (HibernateException he) {
                if (tx!=null) tx.rollback();
                throw he;
            }
            finally {
                session.close();
            }
            return blog;
        }

        public List listBlogsAndRecentItems() throws HibernateException {

            Session session = _sessions.openSession();
            Transaction tx = null;
            List result = null;
            try {
                tx = session.beginTransaction();
                Query q = session.createQuery(
                    "from Blog as blog " +
                    "inner join blog.items as blogItem " +
                    "where blogItem.datetime > :minDate"
                );

                Calendar cal = Calendar.getInstance();
                cal.roll(Calendar.MONTH, false);
                q.setCalendar("minDate", cal);

                result = q.list();
                tx.commit();
            }
            catch (HibernateException he) {
                if (tx!=null) tx.rollback();
                throw he;
            }
            finally {
                session.close();
            }
            return result;
        }
    }

- PrevChapter 24. Example: Parent/Child
- Up
- Home
- NextChapter 26. Example: Various Mappings