Hinbernate 实例

下面的两个持久化类表示一个weblog,和在其中张贴的一个贴子。他们是标准的父/子关系模型，但是我们会用一个排序包（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;    }}

17.2. Hibernate 映射

下列的XML映射应该是很直白的。

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC         "-//Hibernate/Hibernate Mapping DTD 2.0//EN"        "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd"><hibernate-mapping package="eg">    <class         name="Blog"         table="BLOGS"         lazy="true">                <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"             lazy="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 2.0//EN"        "http://hibernate.sourceforge.net/hibernate-mapping-2.0.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>

17.3. Hibernate 代码

下面的类演示了我们可以使用Hibernate对这些类所进行的操作。

package eg;import java.util.ArrayList;import java.util.Calendar;import java.util.Iterator;import java.util.List;import net.sf.hibernate.HibernateException;import net.sf.hibernate.Query;import net.sf.hibernate.Session;import net.sf.hibernate.SessionFactory;import net.sf.hibernate.Transaction;import net.sf.hibernate.cfg.Configuration;import net.sf.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.save(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.list().get(0);            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;    }}