SSH2 框架下的分页

1.设计分页实体（pageBean）

这里我显示的是3-12页的方式：

 package cn.itcast.oa.domain;

 import java.util.List;

 /**
  * 封装分页信息
  * @author zhaoqx
  *
  */
 public class PageBean {
     /**从页面提交过来的参数**/
     private int currentPage;//----当前页码
     private int pageSize;//-------每页显示多少条数据

     /**查询数据库获得**/
     private int recordCount;//----总记录数
     private List recordList;//页面要显示的数据集合

     /**由上面4个计算获得**/
     private int pageCount;//------总页数
     private int beginPageIndex;//-开始页码
     private int endPageIndex;//---结束页码

     public PageBean() {}

     public PageBean(int currentPage, int pageSize, int recordCount,List recordList) {
         this.currentPage = currentPage;
         this.pageSize = pageSize;
         this.recordCount = recordCount;
         this.recordList = recordList;

         pageCount = (this.recordCount + this.pageSize - 1) / this.pageSize;//计算页数

         if(pageCount <= 10){
             this.beginPageIndex = 1;
             this.endPageIndex = this.pageCount;
         }else{
             this.beginPageIndex = this.currentPage - 4;
             this.endPageIndex = this.currentPage + 5;

             if(this.beginPageIndex < 1){
                 this.beginPageIndex = 1;
                 this.endPageIndex = 10;
             }
             if(this.endPageIndex > this.pageCount){
                 this.endPageIndex = this.pageCount;
                 this.beginPageIndex = this.endPageIndex - 9;
             }
         }
     }

     public int getCurrentPage() {
         return currentPage;
     }

     public void setCurrentPage(int currentPage) {
         this.currentPage = currentPage;
     }

     public int getPageCount() {
         return pageCount;
     }

     public void setPageCount(int pageCount) {
         this.pageCount = pageCount;
     }

     public int getPageSize() {
         return pageSize;
     }

     public void setPageSize(int pageSize) {
         this.pageSize = pageSize;
     }

     public int getRecordCount() {
         return recordCount;
     }

     public void setRecordCount(int recordCount) {
         this.recordCount = recordCount;
     }

     public int getBeginPageIndex() {
         return beginPageIndex;
     }

     public void setBeginPageIndex(int beginPageIndex) {
         this.beginPageIndex = beginPageIndex;
     }

     public int getEndPageIndex() {
         return endPageIndex;
     }

     public void setEndPageIndex(int endPageIndex) {
         this.endPageIndex = endPageIndex;
     }

     public List getRecordList() {
         return recordList;
     }

     public void setRecordList(List recordList) {
         this.recordList = recordList;
     }
 }

2.在action里面调用

 package cn.itcast.oa.action;

 import java.util.Date;
 import java.util.List;

 import org.springframework.context.annotation.Scope;
 import org.springframework.stereotype.Controller;

 import cn.itcast.oa.base.BaseAction;
 import cn.itcast.oa.domain.Forum;
 import cn.itcast.oa.domain.PageBean;
 import cn.itcast.oa.domain.Reply;
 import cn.itcast.oa.domain.Topic;
 import cn.itcast.oa.utils.HQLHelper;

 /**
  * 主题操作
  * @author zhaoqx
  *
  */
 @Controller
 @Scope("prototype")
 public class TopicAction extends BaseAction<Topic>{
     private Long forumId;//属性驱动，版块id    

     /**
      * 显示单个主题（回复列表）
      */
     public String show(){
         //根据id查询主题
         Topic topic = topicService.getById(model.getId());
         getValueStack().push(topic);

         //根据主题查询对应的回复列表
         HQLHelper hh = new HQLHelper(Reply.class);
         hh.addWhere("o.topic = ?", model);
         hh.addOrderBy("o.postTime", true);
         PageBean pb = replyService.getPageBean(hh,currentPage);
         getValueStack().push(pb);

         return "show";
     }

     public void setForumId(Long forumId) {
         this.forumId = forumId;
     }

     public Long getForumId() {
         return forumId;
     }
 }

这里的currentPage 是在baseAction里面定义的  代码如下：

1 protected int currentPage = 1;//属性驱动，当前页码
2
3     public int getCurrentPage() {
4         return currentPage;
5     }
6
7     public void setCurrentPage(int currentPage) {
8         this.currentPage = currentPage;
9     }

3.在BaseDaoImpl 里面写

 package cn.itcast.oa.base;

 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.util.List;

 import javax.annotation.Resource;

 import org.hibernate.Query;
 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.springframework.orm.hibernate3.HibernateTemplate;

 import cn.itcast.oa.domain.Book;
 import cn.itcast.oa.domain.PageBean;
 import cn.itcast.oa.utils.HQLHelper;
 /**
  * 通用Dao实现
  * @author zhaoqx
  *
  * @param <T>
  */
 @SuppressWarnings("unchecked")
 public class BaseDaoImpl<T> implements IBaseDao<T> {
     @Resource
     private SessionFactory sessionFactory;

     private Class<T> clazz;

     public BaseDaoImpl() {
         //获得实体类型
         ParameterizedType genericSuperclass = (ParameterizedType) this.getClass().getGenericSuperclass();//获得真正的父类
         Type[] types = genericSuperclass.getActualTypeArguments();
         clazz = (Class<T>) types[0];
     }

     public void save(T entity) {
         getSession().save(entity);
     }

     public void delete(Long id) {
         getSession().delete(getSession().get(clazz, id));
     }

     public void update(T entity) {
         getSession().update(entity);
     }

     public List<T> findAll() {
         String hql = "FROM " + clazz.getSimpleName();
         return getSession().createQuery(hql).list();
     }

     public T getById(Long id) {
         return (T) getSession().get(clazz, id);
     }

     public List<T> getByIds(Long[] ids) {
         String hql = "FROM " + clazz.getSimpleName() + " WHERE id in (:ids)";
         Query query = getSession().createQuery(hql);
         query.setParameterList("ids", ids);//一次赋值多个
         return query.list();
     }

     public Session getSession(){
         return sessionFactory.getCurrentSession();
     }

     /**
      * 公共分页
      */
     public PageBean getPageBean(HQLHelper hh, int currentPage) {
         int pageSize = 5;
         int firstResult = (currentPage - 1) * pageSize;
         String listHQL = hh.getListHQL();
         String countHQL = hh.getCountHQL();
         List<Object> args = hh.getArgs();

         Query query = this.getSession().createQuery(listHQL);
         if(args != null && args.size() > 0){
             int index = 0;
             for(Object o : args){
                 query.setParameter(index++, o);
             }
         }
         query.setFirstResult(firstResult);
         query.setMaxResults(pageSize);
         List recordList = query.list();

         query = this.getSession().createQuery(countHQL);
         if(args != null && args.size() > 0){
             int index = 0;
             for(Object o : args){
                 query.setParameter(index++, o);
             }
         }
         Long recordCount = (Long) query.uniqueResult();

         return new PageBean(currentPage, pageSize, recordCount.intValue(), recordList);
     }

 }

4.最后还有一个工具类:

 package cn.itcast.oa.utils;

 import java.util.ArrayList;
 import java.util.List;

 /**
  * 辅助生成HQL语句的工具类
  * @author zhaoqx
  *
  */
 public class HQLHelper {
     private String fromStr;//FROM 子句
     private String whereStr = "";//WHERE 子句
     private String orderByStr = "";//ORDER BY 子句

     private List<Object> args = new ArrayList<Object>();//封装HQL中对应的参数信息

     public HQLHelper() {}

     /**
      * 通过构造方法拼接FROM 子句
      * @param clazz
      */
     public HQLHelper(Class clazz) {
         this.fromStr = "FROM " + clazz.getSimpleName() + " o ";
     }

     /**
      * 拼接WHERE 子句
      * @param condition
      * @param args
      */
     public void addWhere(String condition,Object...args){//o.name = ?
         if(this.whereStr.length()==0){
             //第一次拼接WHERE子句
             this.whereStr = " WHERE " + condition;
         }else{
             //不是第一次拼接WHERE子句
             this.whereStr += " AND " + condition;
         }
         if(args != null && args.length > 0){
             //封装参数
             for(Object o : args){
                 this.args.add(o);
             }
         }
     }

     /**
      * 拼接ORDER BY 子句
      * @param orderBy
      * @param asc
      */
     public void addOrderBy(String orderBy , boolean asc){
         if(this.orderByStr.length() == 0){
             //第一次拼接ORDER BY 子句
             this.orderByStr = " ORDER BY " + orderBy + (asc ? " ASC " : " DESC ");
         }else{
             //不是第一次拼接ORDER BY 子句
             this.orderByStr += ", " + orderBy + (asc ? " ASC " : " DESC ");
         }
     }

     /**
      * 获取查询List集合的HQL语句
      * @return
      */
     public String getListHQL(){
         return this.fromStr + this.whereStr + this.orderByStr;
     }

     /**
      * 获取查询统计记录数的HQL
      * @param args
      */
     public String getCountHQL(){
         return "SELECT COUNT(*) " + this.fromStr + this.whereStr;
     }

     public void setArgs(List<Object> args) {
         this.args = args;
     }

     public List<Object> getArgs() {
         return args;
     }

 }

好了，这样一个通用的分页就完成啦。。。