分页问题

1.创建一个Page类

package com.hotel.util;

public class Page {
private int nextPage=1;
private int previouPage=1;
private int lastPage=1;
private int firstPage=1;
private int currentPage=1;

public Page(int nowPage,int pageSize,int total){
 this.currentPage=nowPage;
 calcuPage(nowPage,pageSize,total);
}
public void calcuPage(int nowPage,int pageSize,int total) {
 if((nowPage-1)*pageSize>=total){//total为空时
  nowPage-=1;
  currentPage=nowPage;
 }
 
 
 if(nowPage*pageSize<total){
  nextPage=nowPage+1;
 }
 else{
  nextPage=nowPage;
 }
 
 
 if(nowPage<=1){
  previouPage=1;
 }
 else{
  previouPage=nowPage-1;
 }
 
 firstPage=total==0?0:1;
 lastPage=total%pageSize==0?total/pageSize:total/pageSize+1;
}
public int getNextPage() {
 return nextPage;
}
public int getPreviouPage() {
 return previouPage;
}
public int getLastPage() {
 return lastPage;
}
public int getFirstPage() {
 return firstPage;
}
public int getCurrentPage() {
 return currentPage;
}

}

 

 

2.根据当前页和每页大小，查询数据库中的表

   核心sql语句(以emp表为例)

    select * from (select e.*,rownum row_num from emp e where rownum < =currentpage*pagesize) where row_num > (currentpage-1)*pagesize;

 

   

     如果要求查询出的数据进行了排序,可以分为3步走

1.select * from emp where order by empno;记为临时表A

2.select A.*,rownum row_num from A where rownum <= currentpage*pagesize;记为临时表B

3.select * from B where row_num >(currentpage-1)*pagesize;

 

合起来即为

select * from (select A.*,rownum row_num from (select * from emp order by empno ) A where rownum <= 10) where row_num > 0;