mybatis-plus整合SpringBoot之——分页插件使用
Mybatis-plus整合SpringBoot之——分页插件使用
前言
mybatis-plus中的分页插件学习记录：
提示：以下是本篇文章正文内容，下面案例可供参考
一、使用步骤
1.引入依赖
这里使用3.1.1.tmp版本
com.baomidou
mybatis-plus-boot-starter
3.3.1.tmp
2.配置分页插件拦截器
/**
* MyBatisPlus的分页配置
* @Author: yyh
* Date: 2022/5/10
* Time: 21:15
*/
@Configuration
public class MyBatisPlusConfig {
@Bean
public PaginationInterceptor paginationInterceptor() {
return new PaginationInterceptor();
}
}
3.controller层、service层、mapper层
controller
package com.yyh.server.controller;
/**
*
* @author yyh
* @since 2022-04-30
*/
@RestController
@RequestMapping("/employee/basic")
public class EmployeeController {
@Autowired
private IEmployeeService employeeService;
/**
* 分页获取员工：
* 前台可以根据Employee实体类中的属性传入搜索参数，并且还可以传入查询的页码以及每页的数量，
* 默认是第1页，且每页是10条数据
* @param currentPage：当前页码
* @param pageSize：每页数据条数
* @param employee：用于接收搜索参数的实体类
* @param beginDateScope：员工的入职日期范围，这里专门使用一个LocalDate[]数组接收时间范围
* @return
*/
@ApiModelProperty(value = "获取员工，分页查询")
@GetMapping("/")
public RespPageBean getEmployees(@RequestParam(defaultValue = "1") Integer currentPage,
@RequestParam(defaultValue = "10") Integer pageSize,
/*@RequestBody*/ Employee employee,
LocalDate[] beginDateScope
/*HttpServletRequest request*/) {
System.out.println("============");
return employeeService.getEmployeesByPage(currentPage, pageSize, employee, beginDateScope);
}
}
[注意]：不能使用@RequestBody修饰Employee employee、LocalDate[] beginDateScope。因为此处是get类型请求，get是没有请求体的。若为get类型请求的请求参数，加上@RequestBody注解，在用swagger测试的时候，该参数Employee employee会是以表单的形式提交，而get没请求体，所以不符合http协议规范。若使用postman测试的时候，get类型的接口，压根是不能选择传body的。
service
package com.yyh.server.service.impl;
/**
*
* @author yyh
* @since 2022-04-30
*/
@Service
public class EmployeeServiceImpl extends ServiceImpl<EmployeeMapper, Employee> implements IEmployeeService {
@Autowired
private EmployeeMapper employeeMapper;
@Override
public RespPageBean getEmployeesByPage(Integer currentPage, Integer pageSize, Employee employee, LocalDate[] beginDateScope) {
//开启分页
Page<Employee> page = new Page<>(currentPage, pageSize);
//调用mapper层查询方法
IPage<Employee> employeesByPage = employeeMapper.getEmployeesByPage(page, employee, beginDateScope);
long total = employeesByPage.getTotal();
List<Employee> records = employeesByPage.getRecords();
RespPageBean respPageBean = new RespPageBean((int) total, records);
return respPageBean;
}
}
mapper
package com.yyh.server.mapper;
/**
*
* @author yyh
* @since 2022-04-30
*/
public interface EmployeeMapper extends BaseMapper<Employee> {
/**
* 分页查询员工：
* 这里使用的是mybatis-plus的分页工具，所以在mapper层的分页查询方法中
* 传入了分页对象page，mybatis-plus会自动利用aop技术在sql语句中添加上分页查询的参数
* @param page
* @param employee
* @param beginDateScope
* @return
*/
IPage<Employee> getEmployeesByPage(Page<Employee> page,
@Param("employee") Employee employee,
@Param("beginDateScope") LocalDate[] beginDateScope);
}
SQL语句
<?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.yyh.server.mapper.EmployeeMapper">
<!-- 通用查询映射结果 -->
<resultMap id="BaseResultMap" type="com.yyh.server.pojo.Employee">
<id column="id" property="id" />
<result column="name" property="name" />
<result column="gender" property="gender" />
<result column="birthday" property="birthday" />
<result column="idCard" property="idCard" />
<result column="wedlock" property="wedlock" />
<result column="nationId" property="nationId" />
<result column="nativePlace" property="nativePlace" />
<result column="politicId" property="politicId" />
<result column="email" property="email" />
<result column="phone" property="phone" />
<result column="address" property="address" />
<result column="departmentId" property="departmentId" />
<result column="jobLevelId" property="jobLevelId" />
<result column="posId" property="posId" />
<result column="engageForm" property="engageForm" />
<result column="tiptopDegree" property="tiptopDegree" />
<result column="specialty" property="specialty" />
<result column="school" property="school" />
<result column="beginDate" property="beginDate" />
<result column="workState" property="workState" />
<result column="workID" property="workID" />
<result column="contractTerm" property="contractTerm" />
<result column="conversionTime" property="conversionTime" />
<result column="notWorkDate" property="notWorkDate" />
<result column="beginContract" property="beginContract" />
<result column="endContract" property="endContract" />
<result column="workAge" property="workAge" />
<result column="salaryId" property="salaryId" />
</resultMap>
<resultMap id="EmployeeInfoMap" extends="BaseResultMap" type="com.yyh.server.pojo.Employee">
<association property="nation" javaType="com.yyh.server.pojo.Nation">
<id column="nid" property="id"/>
<result column="nname" property="name"/>
</association>
<association property="politicsStatus" javaType="com.yyh.server.pojo.PoliticsStatus">
<id column="psid" property="id"/>
<result column="psname" property="name"/>
</association>
<association property="department" javaType="com.yyh.server.pojo.Department">
<id column="did" property="id"/>
<result column="dname" property="name"/>
</association>
<association property="joblevel" javaType="com.yyh.server.pojo.Joblevel">
<id column="jid" property="id"/>
<result column="jname" property="name"/>
</association>
<association property="position" javaType="com.yyh.server.pojo.Position">
<id column="pid" property="id"/>
<result column="pname" property="name"/>
</association>
</resultMap>
<!-- 通用查询结果列 -->
<sql id="Base_Column_List">
id, name, gender, birthday, idCard, wedlock, nationId, nativePlace, politicId, email, phone, address, departmentId, jobLevelId, posId, engageForm, tiptopDegree, specialty, school, beginDate, workState, workID, contractTerm, conversionTime, notWorkDate, beginContract, endContract, workAge, salaryId
</sql>
<select id="getEmployeesByPage" resultMap="EmployeeInfoMap">
SELECT
e.*,
n.id nid, n.`name` nname,
d.id did, d.`name` dname,
ps.id psid, ps.`name` psname,
p.id pid, p.`name` pname,
j.id jid, j.`name` jname
FROM
t_employee e,
t_nation n,
t_department d,
t_politics_status ps,
t_position p,
t_joblevel j
WHERE
e.nationId = n.id
AND
e.departmentId = d.id
AND
e.politicId = ps.id
AND
e.posId = p.id
AND
e.jobLevelId = j.id
<if test="employee.name != null and employee.name != ''">
AND e.`name` LIKE CONCAT('%',#{employee.name},'%')
</if>
<if test="employee.politicId != null">
AND ps.id = #{employee.politicId}
</if>
<if test="employee.nationId != null">
AND n.id = #{employee.nationId}
</if>
<if test="employee.posId != null">
AND p.id = #{employee.posId}
</if>
<if test="employee.jobLevelId != null">
AND j.id = #{employee.jobLevelId}
</if>
<if test="employee.departmentId != null">
AND d.id = #{employee.departmentId}
</if>
<if test="beginDateScope != null">
AND e.beginDate BETWEEN #{beginDateScope[0]} AND #{beginDateScope[1]}
</if>
ORDER BY e.id
</select>
</mapper>
总结
使用mybatis-plus分页插件的时候，执行的是真正的物理分页。
首先会查询记录条数：
Preparing: SELECT COUNT(1) FROM t_employee e, t_nation n, t_department d, t_politics_status ps, t_position p, t_joblevel j WHERE e.nationId = n.id AND e.departmentId = d.id AND e.politicId = ps.id AND e.posId = p.id AND e.jobLevelId = j.id
再进行物理分页，直接在SQL语句中拼接limit：
SELECT e.*, n.id nid, n.`name` nname, d.id did, d.`name` dname, ps.id psid, ps.`name` psname, p.id pid, p.`name` pname, j.id jid, j.`name` jname FROM t_employee e, t_nation n, t_department d, t_politics_status ps, t_position p, t_joblevel j WHERE e.nationId = n.id AND e.departmentId = d.id AND e.politicId = ps.id AND e.posId = p.id AND e.jobLevelId = j.id ORDER BY e.id LIMIT ?,?
若直接使用BaseMapper接口中的selectPage()方法完成分页，实质上是先获得全部数据，缓存之后，再进行分页，但如果数据量过多时，查询全部数据是不可取的。
两种区别可以通过控制台打印的SQL语句区别。