Spring|Spring Boot 集成PageHelper的使用方法 SpringBoot集成PageHelper的使用方法

前言：
一、基本集成

引入jar包
Yml配置文件中添加相关配置
封装相关分页方法
示例代码
前段传入参数
执行结果

二、分页中的排序字段如何防止SQL注入问题

三、复杂的SQL分页语句

四、分页失效的常见的场景有哪些？

五、大表数据PageHelper分页性能如何

总结：

前言：项目中数据分页是一个很常见的需求，目前大部分项目都会使用pagehelper进行分页，那么在使用的过程中是否考虑如下问题？

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一、基本集成
引入jar包

com.github.pagehelperpagehelper-spring-boot-starter${pagehelper.version}

Yml配置文件中添加相关配置

pagehelper:helperDialect: mysqlreasonable: truesupportMethodsArguments: trueparams: count=countSql

封装相关分页方法

分页参数类 public class PageParam implements Serializable{private static final long serialVersionUID = -7916211163897873899L; private int pageNum=1; private int pageSize=10; //条件参数private T param; //排序字段private String orderBy; public int getPageSize(){return pageSize; }public void setPageSize(int pageSize){this.pageSize = pageSize; }public int getPageNum(){return pageNum; }public void setPageNum(int pageNum){this.pageNum = pageNum; }public T getParam(){return param; }public void setParam(T param){this.param = param; }public String getOrderBy(){return orderBy; }public void setOrderBy(String orderBy){//需要注意sql注入this.orderBy = orderBy; }}分页结果类public class PagedList implements Serializable{private static final long serialVersionUID = -1253790062865437768L; private int pageNum = 1; private List data = https://www.it610.com/article/null; private int pageCount = 0; private int recordCount = -1; private int pagingType = 0; private int pageSize; private String orderBy; /*** @return the pageSize*/public int getPageSize(){return pageSize; }/*** @param pageSize*the pageSize to set*/public void setPageSize(int pageSize){if (pageSize <= 0){return; }this.pageSize = pageSize; }/*** @return the pageCount*/public int getPageCount(){return pageCount; }/*** @param pageCount*the pageCount to set*/public void setPageCount(int pageCount){if (pageCount <= 0){return; }this.pageCount = pageCount; }/*** @return the recordCount*/public int getRecordCount(){return recordCount; }/*** @param recordCount*the recordCount to set*/public void setRecordCount(int recordCount){this.recordCount = recordCount; calcPageCount(); }private void calcPageCount(){if (this.recordCount < 0){return; }int tmp = this.recordCount % getPageSize(); this.pageCount = (tmp == 0 ? (this.recordCount / getPageSize()): (this.recordCount / getPageSize() + 1)); if (this.pageNum> this.pageCount && this.pageCount != 0){this.pageNum = this.pageCount; }this.pageNum = this.pageCount; }public void setData(List data){this.data = https://www.it610.com/article/data; if (ObjectUtil.isNotEmpty(data) && this.recordCount == -1){this.recordCount = data.size(); }}public List getData(){return data; }/*** @return the pagingType*/public int getPagingType(){return pagingType; }/*** @param pagingType*the pagingType to set*/public void setPagingType(int pagingType){this.pagingType = pagingType; }public void setOrderBy(String orderBy){this.orderBy = orderBy; }public int getPageNum(){return pageNum; }public void setPageNum(int pageNum){this.pageNum = pageNum; }public String getOrderBy(){return orderBy; }}分页工具类public class PageUtils implements Serializable{private static final long serialVersionUID = 377943433889798799L; public static PagedList exportPagedList(PageParam pageParam){PagedList pl = new PagedList(); // pagesizeint pageSize = pageParam.getPageSize(); if (pageSize <= 0){pageSize = 10; }else{pl.setPageSize(pageSize); }int pageNum= pageParam.getPageNum(); pl.setPageNum(pageNum); String orderBy= pageParam.getOrderBy(); if(StringUtil.isNotEmpty(orderBy)){//防止sql注入String orderBySql=SQLFilter.sqlInject(orderBy); pl.setOrderBy(orderBySql); }return pl; }public static PagedList toPageList(PageInfo spage){PagedList pagedList = new PagedList(); pagedList.setPageSize((int) spage.getPageSize()); pagedList.setPageNum((int) spage.getPageNum()); pagedList.setRecordCount((int) spage.getTotal()); pagedList.setData(spage.getList()); pagedList.setPageCount((int) spage.getPages()); return pagedList; }}

示例代码

@PostMapping("getPageList")public Result getPageList(@RequestBody PageParam pageParm){//接收参数PagedList pl =PageUtils.exportPagedList(pageParm); return Result.success(userService.queryPageList(pl, pageParm.getParam())); }public PagedList queryPageList(PagedList page,TUser user){PageInfo pageInfo= PageHelper.startPage(page).doSelectPageInfo(()-> list(user)); //转换结果return PageUtils.toPageList(pageInfo); }

前段传入参数

{"pageSize":10,"pageNum":"1",//查询条件"param":{"name":"张三210001"},//排序字段"orderBy":"age desc"}

执行结果

2022-04-15 22:26:39.914 [http-nio-9090-exec-9] DEBUG [613920d89eb54bfd8601c93ec8572dcf] c.s.f.m.UserMapper.queryPageList - ==>Preparing: SELECT * FROM t_user u LEFT JOIN t_user_role ur ON ur.userOid = u.oid WHERE name = ? order by age desc LIMIT ?
2022-04-15 22:26:39.919 [http-nio-9090-exec-9] DEBUG [613920d89eb54bfd8601c93ec8572dcf] c.s.f.m.UserMapper.queryPageList - ==> Parameters: 张三210001(String), 10(Integer)
2022-04-15 22:26:40.267 [http-nio-9090-exec-9] DEBUG [613920d89eb54bfd8601c93ec8572dcf] c.s.f.m.UserMapper.queryPageList - <==Total: 1

基础的分页查询已经发完成了，下面解答上面的问题的方法

二、分页中的排序字段如何防止SQL注入问题对于前段传入的排序字段，我们需要进行SQL过滤处理，关于这个问题其实在上述的分页封装类中已经进行了解决

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示例代码：

public class SQLFilter{public static String sqlInject(String str){if (StringUtil.isBlank(str)){return null; }// 去掉'|"|; |\字符str = StringUtil.replace(str, "'", ""); str = StringUtil.replace(str, "\"", ""); str = StringUtil.replace(str, "; ", ""); str = StringUtil.replace(str, "\\", ""); // 转换成小写str = str.toLowerCase(); // 非法字符String[] keywords = { "master", "truncate", "insert", "select","delete", "update", "declare", "alert", "drop" }; // 判断是否包含非法字符for (String keyword : keywords){if (str.indexOf(keyword) != -1){throw new SysException("包含非法字符"); }}return str; }}

三、复杂的SQL分页语句 【Spring|Spring Boot 集成PageHelper的使用方法】复杂的SQL分页语句，需要自定义SQL的count语句如何实现呢？
PageHelper实现分页，默认是查询自定义的count语句是否存在，如果存在就用自定义的语句，否则就在外层包装查询的语句，而自定义count语句只需要在在查询语句名称后面添加_COUNT即可。例如
查询集合的语句名称为queryPageList，那么查询count的语句为queryPageList_COUNT，返回Long类型即可。

select count(1) from t_useru left join t_user_role ur on ur.userOid=u.oidname=#{name}

四、分页失效的常见的场景有哪些？ 1.pageHelper分页查询有个特殊的要求，查询下sql语句一定要紧跟在分页查询的后面，否则分页查询会失效。之前采用的如下写法容易失效，建议采用java8的写法

PageHelper.startPage(pagedList.getPageNum(),pagedList.getPageSize()); //紧跟分页查询后面List list = list(user); PageInfo pageInfo =new PageInfo<>(list); return PageUtils.toPageList(pageInfo);

2.注意pagehelper的reasonable 默认为false，遇到查询页数大于总页数时，出现分页失败
pagehelper的reasonable 默认为false，遇到查询页数大于总页数时，查询为空；当reasonable设置为true时，遇到查询页数大于总页数时，查询最后一页数据；
3.PageHelper先开启分页，后对list数据操作将会导致分页错误
示例代码：

public PageInfo getUserPageList(int pageNum, int pageSize) {PageHelper.startPage(pageNum,pageSize); List tUserVOsByView = userMapper.getUserList(); List TUserVOs = new ArrayList<>(); for (TUserVO TUserVO : tUserVOsByView) {TUserVO TUserVOSingle = new TUserVO(); TUserVOSingle.setHdId(TUserVO.getHdId()); TUserVOs.add(TUserVOSingle); }PageInfo pageViewInfo = new PageInfo<>(TUserVOs); return pageViewInfo; }

4.PageHelper先对list数据操作，后开启分页，将会导致分页失效
示例代码：

public PageInfo getUserPageList(int pageNum, int pageSize) {List tUserVOsByView = userMapper.getUserList(); List TUserVOs = new ArrayList<>(); for (TUserVO TUserVO : tUserVOsByView) {TUserVO TUserVOSingle = new TUserVO(); TUserVOSingle.setHdId(TUserVO.getHdId()); }PageHelper.startPage(pageNo,pageSize); PageInfo pageViewInfo = new PageInfo<>(TUserVOs); return pageViewInfo; }

大家需要注意下，抽时间可以去验证下结果。

五、大表数据PageHelper分页性能如何 PageHelper 对于大表查询数据量越大，性能越差，这是因为PageHelper分页是自动在sql语句后面拼接limit没有进行相关的优化，一旦数据大，性能就比较慢。
例如：
优化前SQL语句：

SELECT d.* FROM tag_detail d LIMIT 10000000,10

查询的时间大概需要10秒左右，执行速度比较慢。
优化后SQL语句：

SELECT d.* FROM tag_detail dINNER JOIN (SELECT oid FROM tag_detail LIMIT 10000000,10) tON d.oid= t.oid;

子查询先通过分页查询主键字段，然后进行关联查询，经过优化后，查询时间大概为1秒左右。性能大幅度提升。

总结：本文讲解了PageHelper的基本的使用和相关的问题，这些都是我从实际的项目中总结出来的问题以及相关的解决方案，大家在使用的时候要特别注意，不要放同样的错误。
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