Question

jsp分页Dao类中怎么写

从jsp页面中传一个参数page页数

Answer 1

只穿页数？那就是固定了一页多少条吧？
你看看参考资料，它是用了在jsp页面上直接分页，你可以把他思想拿过来然后封装成dao类
你是用list分页的话我建议你不要那样，如果数据到了一定程度就会很慢的。
最好是用存储过程分页

下面这个可以参考一下

if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[p_show]') and OBJECTPROPERTY(id, N'IsProcedure') = 1)
drop procedure [dbo].[p_show]
GO

CREATE Proc p_show
@QueryStr nvarchar(4000), --表名、视图名、查询语句
@PageSize int=10, --每页的大小(行数)
@PageCurrent int=1, --要显示的页
@FdShow nvarchar (4000)='', --要显示的字段列表,如果查询结果有标识字段,需要指定此值,且不包含标识字段
@FdOrder nvarchar (1000)='' --排序字段列表
as
declare @FdName nvarchar(250) --表中的主键或表、临时表中的标识列名
,@Id1 varchar(20),@Id2 varchar(20) --开始和结束的记录号
,@Obj_ID int --对象ID
--表中有复合主键的处理
declare @strfd nvarchar(2000) --复合主键列表
,@strjoin nvarchar(4000) --连接字段
,@strwhere nvarchar(2000) --查询条件

select @Obj_ID=object_id(@QueryStr)
,@FdShow=case isnull(@FdShow,'') when '' then ' *' else ' '+@FdShow end
,@FdOrder=case isnull(@FdOrder,'') when '' then '' else ' order by '+@FdOrder end
,@QueryStr=case when @Obj_ID is not null then ' '+@QueryStr else ' ('+@QueryStr+') a' end

--如果显示第一页，可以直接用top来完成
if @PageCurrent=1
begin
select @Id1=cast(@PageSize as varchar(20))
exec('select top '+@Id1+@FdShow+' from '+@QueryStr+@FdOrder)
return
end

--如果是表,则检查表中是否有标识更或主键
if @Obj_ID is not null and objectproperty(@Obj_ID,'IsTable')=1
begin
select @Id1=cast(@PageSize as varchar(20))
,@Id2=cast((@PageCurrent-1)*@PageSize as varchar(20))

select @FdName=name from syscolumns where id=@Obj_ID and status=0x80
if @@rowcount=0 --如果表中无标识列,则检查表中是否有主键
begin
if not exists(select 1 from sysobjects where parent_obj=@Obj_ID and xtype='PK')
goto lbusetemp --如果表中无主键,则用临时表处理

select @FdName=name from syscolumns where id=@Obj_ID and colid in(
select colid from sysindexkeys where @Obj_ID=id and indid in(
select indid from sysindexes where @Obj_ID=id and name in(
select name from sysobjects where xtype='PK' and parent_obj=@Obj_ID
)))
if @@rowcount>1 --检查表中的主键是否为复合主键
begin
select @strfd='',@strjoin='',@strwhere=''
select @strfd=@strfd+',['+name+']'
,@strjoin=@strjoin+' and a.['+name+']=b.['+name+']'
,@strwhere=@strwhere+' and b.['+name+'] is null'
from syscolumns where id=@Obj_ID and colid in(
select colid from sysindexkeys where @Obj_ID=id and indid in(
select indid from sysindexes where @Obj_ID=id and name in(
select name from sysobjects where xtype='PK' and parent_obj=@Obj_ID
)))
select @strfd=substring(@strfd,2,2000)
,@strjoin=substring(@strjoin,5,4000)
,@strwhere=substring(@strwhere,5,4000)
goto lbusepk
end
end
end
else
goto lbusetemp

/*--使用标识列或主键为单一字段的处理方法--*/
lbuseidentity:
exec('select top '+@Id1+@FdShow+' from '+@QueryStr
+' where '+@FdName+' not in(select top '
+@Id2+' '+@FdName+' from '+@QueryStr+@FdOrder
+')'+@FdOrder
)
return

/*--表中有复合主键的处理方法--*/
lbusepk:
exec('select '+@FdShow+' from(select top '+@Id1+' a.* from
(select top 100 percent * from '+@QueryStr+@FdOrder+') a
left join (select top '+@Id2+' '+@strfd+'
from '+@QueryStr+@FdOrder+') b on '+@strjoin+'
where '+@strwhere+') a'
)
return

/*--用临时表处理的方法--*/
lbusetemp:
select @FdName='[ID_'+cast(newid() as varchar(40))+']'
,@Id1=cast(@PageSize*(@PageCurrent-1) as varchar(20))
,@Id2=cast(@PageSize*@PageCurrent-1 as varchar(20))

exec('select '+@FdName+'=identity(int,0,1),'+@FdShow+'
into #tb from'+@QueryStr+@FdOrder+'
select '+@FdShow+' from #tb where '+@FdName+' between '
+@Id1+' and '+@Id2
)

GO

Answer 2

jsp分页的dao类里面主要是执行sql分页的实现过程。
写法参考如下：

public class PageDao {
public PageDao() {
}
public List pageData(int currentPage, int pageCount) {
List results = new ArrayList();
String tableName = "demo_userinfo_pages";
ResultSet rs = null;
StringBuffer sql = new StringBuffer("");
Statement stmt = null;
Connection conn = null;
try {
int count = recordCount();
int totalPage = (int) Math.ceil(1.0 * count / pageCount);
int start = 0;
int end = 0;
if (currentPage <= 0) {
currentPage = 1;
start = 1;
end = currentPage * pageCount;
}

if (currentPage > totalPage) {
currentPage = totalPage;
return results;
}
if ((currentPage - 1) * pageCount >= 0) {
start = (currentPage - 1) * pageCount + 1;
end = currentPage * pageCount;
}
sql.append("SELECT * ").append("FROM (SELECT a.*,ROWNUM rn ")
.append(" FROM (SELECT * ").append(" FROM " + tableName)
.append(" ORDER BY asc) a").append(" )").append(
" WHERE rn >= " + start + " and rn <=" + end);

conn = DBManager.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery(sql.toString());
while (rs.next()) {
UserForm bean = new UserForm();
bean.setUserid(rs.getInt("USERID"));
bean.setUsername(rs.getString("USERNAME"));
results.add(bean);
}
} catch (Exception exception) {
exception.printStackTrace();
} finally {
closeJDBCResource(stmt);
closeJDBCResource(rs);
closeJDBCResource(conn);
}
return results;
}