两个字母搞定J2EE通用分页标签(二)

作者:张纪豪(转载请注明出处)

(三)、数据访问层设计与数据分页

 

    数据访问层的设计非常重要，在一个较大的项目中，应该利用泛型技术做一个公共数据访问组件，由于本主题要阐述的是分页，所以不搞那么复杂。也因如此，服务层内容也省掉。

    在com.zhangjihao.dao包中建立两个接口和两个对应的实现类：

BookDao接口 

package com.zhangjihao.dao;import java.util.List;import com.zhangjihao.bean.Page;import com.zhangjihao.domain.Book;public interface BookDao {public abstract void save(Book book);public abstract void update(Book book);public abstract void delete(Book book);public abstract Book getBook(Integer id);//数据分页public abstract List listAllBooks(Page page);} 

BookDaoImpl数据访问组件 

package com.zhangjihao.dao;import java.util.List;import javax.annotation.Resource;import org.hibernate.Query;import org.hibernate.SessionFactory;import com.zhangjihao.bean.Page;import com.zhangjihao.domain.Book;@Repository("BookDao")  //交给Spring管理@Transactional          //声明Spring管理事务 public class BookDaoImpl implements BookDao {         //在Spring容器里取得Hibernate的session工厂对象@Resource protected SessionFactory sessionFactory;public void save(Book book) {sessionFactory.getCurrentSession().persist(book);}public void update(Book book) {sessionFactory.getCurrentSession().merge(book);}public void delete(Book book){sessionFactory.getCurrentSession().delete(book);}public Book getBook(Integer id) {return (Book)sessionFactory.getCurrentSession().get(Book.class, id);}//数据分页@SuppressWarnings("unchecked")public List listAllBooks(Page page) {Query query = sessionFactory.getCurrentSession().createQuery("select count(*) from Book");//得到总记录并保存到page对象中long l = (Long)query.uniqueResult();page.setTotalCount((int)l);query = sessionFactory.getCurrentSession().createQuery("from Book");//注意下面这个分页参数query.setFirstResult(page.getFirst()).setMaxResults(page.getPageSize()).setFetchSize(page.getPageSize());return query.list();}} 

NewsDao接口 

package com.zhangjihao.dao;import java.util.List;import com.zhangjihao.bean.Page;import com.zhangjihao.domain.News;public interface NewsDao {public abstract void save(News news);public abstract void update(News news);public abstract void delete(News news);public abstract News getNews(Integer id);//数据分页public abstract List listAllNews(Page page);} 

NewsDaoImpl数据访问组件 

package com.zhangjihao.dao;import java.util.List;import javax.annotation.Resource;import org.hibernate.Query;import org.hibernate.SessionFactory;import org.springframework.stereotype.Repository;import org.springframework.transaction.annotation.Transactional;import com.zhangjihao.bean.Page;import com.zhangjihao.domain.News;@Repository("NewsDao") //交给Spring管理@Transactional //声明Spring管理事务 public class NewsDaoImpl implements NewsDao {@Resource protected SessionFactory sessionFactory;public void save(News news) {sessionFactory.getCurrentSession().save(news);}public void delete(News news) {sessionFactory.getCurrentSession().delete(news);}public void update(News news) {sessionFactory.getCurrentSession().merge(news);}public News getNews(Integer id) {return (News)sessionFactory.getCurrentSession().get(News.class, id);}public List listAllNews(Page page) {Query query = sessionFactory.getCurrentSession().createQuery("select count(*) from News");//得到总记录并保存到page对象中long l = (Long)query.uniqueResult();page.setTotalCount((int)l);query = sessionFactory.getCurrentSession().createQuery("from News");//注意下面这个分页参数query.setFirstResult(page.getFirst()).setMaxResults(page.getPageSize()).setFetchSize(page.getPageSize());return query.list();}}

listAllBooks和listAllNews 两方法返回的就是一页的数据。