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【Java】【33】分页处理
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内容图文
前言：
数据量太大时，前端就需要做翻页显示了，即点击第几页就拉取第几页的数据
正文：
1，在xml中写查询语句
Service层
注：用了rowBounds其实就是假分页了，会把数据查到内存里来，再去对应的数据集合给到前端。真分页的话，数据库查询XML里Oracle和MySQL写法不同，要注意
@Autowired TheDao theDao;
public PageModel<UserVo> getClerkListByBlur(QueryVo query) {
RowBounds rowBounds = new RowBounds((query.getPage() - 1) * query.getRows(), query.getRows());
int total = this.theDao.getCount(query);
PageModel<UserVo> pageModel = new PageModel<UserVo>();
pageModel.setPageNo(query.getPage());
pageModel.setPageSize(query.getRows());
pageModel.setTotalRecords(total);
List<UserVo> list = this.theDao.getList(query, rowBounds); //rowBounds pageModel.setList(list);
return pageModel;
}
Dao层
int
getCount(QueryVo info);
List<UserVo> getList(QueryVo info, RowBounds rowBounds);
数据库查询XML
<?
xml version="1.0" encoding="UTF-8"
?>
<!
DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"
>
<
mapper
namespace
="com.bf.dnh.dao.ClerkDao"
>
<
resultMap
id
="UserVoMap"
type
="com.bf.xx.params.base.UserVo"
>
<
id
column
="Id"
property
="id"
jdbcType
="VARCHAR"
/>
<
result
column
="Name"
property
="name"
jdbcType
="VARCHAR"
/>
<
result
column
="Province"
property
="province"
jdbcType
="VARCHAR"
/>
<
result
column
="City"
property
="city"
jdbcType
="VARCHAR"
/>
<
result
column
="Gender"
property
="gender"
jdbcType
="SMALLINT"
/>
<
result
column
="Create_Time"
property
="createTime"
jdbcType
="TIMESTAMP"
/>
</
resultMap
>
<
select
id
="getCount"
resultType
="int"
>
select count(1) from (
<
include
refid
="sql_getList"
/>
) T
</
select
>
<
select
id
="getList"
resultMap
="UserVoMap"
>
<
include
refid
="sql_getList"
/>
ORDER BY T.CREATE_TIME DESC
</
select
>
-- mysql 真分页写法
<
select
id
="getTestList"
resultMap
="UserVoMap"
>
SELECT T.*
FROM USER T
ORDER BY T.NAME DESC
<
if
test
="page != 0"
>
LIMIT #{start}, #{rows}
</
if
>
</
select
>
<
sql
id
="sql_getList"
>
SELECT T.*
FROM USER T
WHERE T.STATUS = 1
<
if
test
="keyword != null and keyword != ‘‘"
>
AND T.NAME LIKE ‘%${keyword}%‘
</
if
>
</
sql
>
</
mapper
>
2，mybatis的映射查询
Service层
@Autowired TheMapper theMapper;
public PageModel<UserVo> getClerkListByBlur(QueryVo query) {
Example example = new Example(QueryVo.class);
example.createCriteria()
.andEqualTo("status", 1)
.andLike("name", query.getKeyword());
PageModel<UserVo> pageModel = new PageModel<UserVo>();
pageModel.setPageNo(query.getPage());
pageModel.setPageSize(query.getRows());
int total = this.theMapper.selectCountByExample(query);
pageModel.setTotalRecords(total);
RowBounds rowBounds = new RowBounds((query.getPage() - 1) * query.getRows(), query.getRows());
List<UserVo> list = this.theMapper.selectByExampleAndRowBounds(example, rowBounds);
pageModel.setList(list);
return pageModel;
}
Dao层
import
com.bf.base.entity.QueryVo;
import
org.springframework.stereotype.Repository;
import
tk.mybatis.mapper.common.Mapper;
@Repository
public
interface TheMapper extends Mapper<QueryVo> {
}
3，基础类
QueryVo类
public
class
QueryVo {
private
int page; //页数privateint rows; //每页显示条数private String keyword;
publicint getPage() {
return page;
}
publicvoid setPage(int page) {
this.page = page;
}
publicint getRows() {
return rows;
}
publicvoid setRows(int rows) {
this.rows = rows;
}
public String getKeyword() {
return keyword;
}
publicvoid setKeyword(String keyword) {
this.keyword = keyword;
}
}
-- 真分页的话，需要增加一个参数start，开始条数
private
int start; //由page*rows计算得来publicint getStart() {
start = (page - 1) * rows;
return start;
}
publicvoid setStart(int start) {
this.start = start;
}
PageModel类
package
com.bf.base.params;
import
java.util.List;
/**
* 封装分页信息
*
*/
public
class PageModel<E> {
//结果集private List<E> list;
//查询记录数privateint totalRecords;
//每页多少条数据privateint pageSize;
//第几页privateint pageNo;
@Override
public String toString() {
return "PageModel [list=" + list + ", totalRecords=" + totalRecords + ", pageSize=" + pageSize + ", pageNo="
+ pageNo + "]";
}
/**
* 总页数
* @return*/publicint getTotalPages() {
return (totalRecords + pageSize - 1) / pageSize;
}
/**
* 取得首页
* @return*/publicint getTopPageNo() {
return 1;
}
/**
* 上一页
* @return*/publicint getPreviousPageNo() {
if (pageNo <= 1) {
return 1;
}
return pageNo - 1;
}
/**
* 下一页
* @return*/publicint getNextPageNo() {
if (pageNo >= getBottomPageNo()) {
return getBottomPageNo();
}
return pageNo + 1;
}
/**
* 取得尾页
* @return*/publicint getBottomPageNo() {
return getTotalPages();
}
public List<E> getList() {
return list;
}
publicvoid setList(List<E> list) {
this.list = list;
}
publicint getTotalRecords() {
return totalRecords;
}
publicvoid setTotalRecords(int totalRecords) {
this.totalRecords = totalRecords;
}
publicint getPageSize() {
return pageSize;
}
publicvoid setPageSize(int pageSize) {
this.pageSize = pageSize;
}
publicint getPageNo() {
return pageNo;
}
publicvoid setPageNo(int pageNo) {
this.pageNo = pageNo;
}
}
原文：https://www.cnblogs.com/huashengweilong/p/11122753.html
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