springboot使用PageHelper插件进行分页查询
目录
最近我在学习利用分页插件来实现分页查询数据，今天给搭建分享一下PageHelper分页插件的学习
环境搭建
springboot（父依赖version 2.0.7）+maven
首先导入pom.xml依赖
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.4.1</version>
</dependency>
< --springboot必须依赖 -->
我这里是用的是1.4.1的版本，建议大家使用最新版本，因为使用旧版本可能会出现循环依赖的问题，还有就是旧版本可能与springboot版本冲突的问题（springboot2.6禁止循环依赖）
如下图使用1.3.0版本报错：
然后我去了解了一下循环依赖，大致就是说 假如bean A依赖于bean B时，bean B又依赖于bean A：bean A --> bean B --> bean A。当没有循环依赖时，bean A --> bean B --> bean C。
当Spring上下文加载所有bean时，它会尝试按照它们工作所需的顺序去创建bean。没有循环依赖时，Spring将创建bean C，然后创建bean B（并将bean C注入其中），然后创建bean A（并将bean B注入其中）。但当有循环依赖时，Spring无法决定应该首先创建哪个bean，因为它们彼此依赖。在这些情况下，Spring将在加载上下文时引发BeanCurrentlyInCreationException。
参考文章 : 什么是循环依赖以及解决方式
配置properties/yml文件
application.properties配置：
# pageHelper分页
# 指定数据库 默认自动检测数据库类型
pagehelper.helperDialect=mysql
# 是否启用分页合理化：当pageNum<1时，会自动查询第一页的数据，当pageNum>pages时，自动查询最后一页数据；
pagehelper.reasonable=true
# 默认值false，分页插件会从查询方法的参数值中，自动根据上面 params 配置的字段中取值，查找到合适的值时就会自动分页。
pagehelper.supportMethodsArguments=true
# 用于从对象中根据属性名取值
pagehelper.params=count: countSql
application.yml配置：
# 分页
# 指定数据库 默认自动检测数据库类型
pagehelper:
helperDialect: mysql
# 是否启用分页合理化：当pageNum<1时，会自动查询第一页的数据，当pageNum>pages时，自动查询最后一页数据；
reasonable: true
# 默认值false，分页插件会从查询方法的参数值中，自动根据上面 params 配置的字段中取值，查找到合适的值时就会自动分页。
supportMethodsArguments: true
# 用于从对象中根据属性名取值
params=count: countSql
代码部分
实体类pojo/entity
@TableId(value = "id", type = IdType.AUTO)
private Integer id;
private String name;
private String address;
controller层
public PageInfo<Address> getListByPage(
@RequestParam(value = "pageNo",defaultValue = "1") Integer pageNo,
@RequestParam(value = "pageSize",defaultValue = "10") Integer pageSize,
@RequestParam("searchValue") String searchValue){
PageHelper.startPage(pageNo,pageSize);
List<Address> addresses = this.addressService.getListByPage(searchValue);
PageInfo<Address> addressPageInfo = new PageInfo<>(addresses);
return addressPageInfo;
}
传入参数 pageNo–当前页，pageSize–每页条数，searchValue–模糊查询
PageHelper.startPage(pageNum, pageSize);
pageNum是 当前页数，pageSize是 每页的条数。
数据查询完后使用PageInfo
PageInfo<实体类> pageInfo = new PageInfo<>(查询结果);
serviceI
List<Address> getListByPage(String searchValue);
serviceImpl
public List<Address> getListByPage(String searchValue) {
List<Address> listByPage = this.addressMapper.getListByPage(searchValue);
return listByPage;
}
mapper
List<Address> getListByPage(String searchValue);
mapper.xml
<select id="getListByPage" resultType="com.lee.testaddress.entity.Address">
select
id, name, address
from
t_address
<where>
<if test="searchValue != null and searchValue != ''">
and name like concat ('%',#{searchValue},'%')
</if>
</where>
</select>
在这里pageHelper已经帮我们做好分页了，所以我们在sql语句中就不用再加分页limit了
pageInfo其它属性
pageNum：当前页码
pageSize：每页数据的数据条数
size：当前页有多少条数据
startRow：当前页码第一条数据的
endRow：当前页码的开始条
pages：当前页码结束条
navigateFirstPage：首页号
navigateLastPage：尾页号
prePage：上一页
nextPage：下一页
isFirstPage：是否为第一页
isLastPage：是否为最后一页
hasPreviousPage：是否有前一页
hasNextPage：是否有下一页
navigatePages：导航页码数
navigatepageNums：导航页码数 可以遍历
测试
通过Apifox或者Postman测试，我这里使用Apifox进行测试
我表中有40条数据
我先设置查询每页条数pageSize为10
得到数据，对照pageInfo其它属性获得变量含义
{
"total": 40,
"list": [
{
"id": 1,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 2,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 3,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 4,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 5,
"name": "lisi",
"address": "Shanghai"
},
{
"id": 6,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 7,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 8,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 9,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 10,
"name": "wangwu",
"address": "Shenzhen"
}
],
"pageNum": 1,
"pageSize": 10,
"size": 10,
"startRow": 1,
"endRow": 10,
"pages": 4,
"prePage": 0,
"nextPage": 2,
"isFirstPage": true,
"isLastPage": false,
"hasPreviousPage": false,
"hasNextPage": true,
"navigatePages": 8,
"navigatepageNums": [
1,
2,
3,
4
],
"navigateFirstPage": 1,
"navigateLastPage": 4
}
然后我设置每页查询50条数据，这样我表中的所有数据全部在第一页查出
{
"total": 40,
"list": [
{
"id": 1,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 2,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 3,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 4,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 5,
"name": "lisi",
"address": "Shanghai"
},
{
"id": 6,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 7,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 8,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 9,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 10,
"name": "wangwu",
"address": "Shenzhen"
},
{
"id": 11,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 12,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 13,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 14,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 15,
"name": "zhaoliu",
"address": "Nanjing"
},
{
"id": 16,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 17,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 18,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 19,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 20,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 21,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 22,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 23,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 24,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 25,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 26,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 27,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 28,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 29,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 31,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 32,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 33,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 34,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 35,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 36,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 37,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 38,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 39,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 41,
"name": "zhangsan",
"address": "Beijing"
},
{
"id": 42,
"name": "zhangsan",
"address": "Beijing"
}
],
"pageNum": 1,
"pageSize": 50,
"size": 40,
"startRow": 1,
"endRow": 40,
"pages": 1,
"prePage": 0,
"nextPage": 0,
"isFirstPage": true,
"isLastPage": true,
"hasPreviousPage": false,
"hasNextPage": false,
"navigatePages": 8,
"navigatepageNums": [
1
],
"navigateFirstPage": 1,
"navigateLastPage": 1
}
模糊查询
查询name中带有lisi的数据
idea打印sql日志
Apifox返回结果，对照数据库，查询结果正确
查询name中带有i的数据
Apifox返回结果，对照数据库，查询结果正确
结语
文章可能有点长，但是都是一点一滴学习的见证
刚进入开发行业还有我很多学习的地方，我很愿意和大家分享我以后学习的过程，感谢阅读！