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## 第 25 章 示例：Weblog 应用程序

## 25.1. 持久化类（Persistent Classes）

下面的持久化类表示一个 weblog 和在其中张贴的一个贴子。他们是标准的父/子关系模型，但是我们会用一个有序包（ordered bag）而非集合（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 映射

下列的 XML 映射应该是很直白的。例如：

    <?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 代码

下面的类演示了我们可以使用 Hibernate 对这些类进行的一些操作：

    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;

        }

    }

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