第 17 章 示例：Weblog 应用程序 - Hibernate reference 2.1.8 ga 正式版中文参考手册

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;
    }
}

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>

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;
    }
}