最近刚入职新公司，项目是从零开始搭建的项目。我觉得是时候考验是驴还是千里马的时候。都是泪就不多说了。
附上一篇Mybatis常用的分页案例。这次要做的是最常见的分页效果，也是基础功能。但是很多人都做不好的。这次采用Mybatis分页插件PageHelper。
仅献给伸手党的大爷们。大爷们好！拿代码记得扣666！！小的在这给感谢了！！一、项目结构
按照controller,service,mapper(也叫dao)来建立项目，utils里面是两个自己写的分页工具类。看前
端需要什么分页参数，你方便添加。并能返回给他
二、插件引入
1.pom.xml。引入PageHelper插件
4.0.0 org.springframework.boot spring-boot-starter-parent2.5.6 com.simons SimonsStudio0.0.1-SNAPSHOT SimonsStudio SimonsStudio 1.8 org.springframework.boot spring-boot-starter-weborg.mybatis.spring.boot mybatis-spring-boot-starter2.2.0 mysql mysql-connector-javaruntime org.springframework.boot spring-boot-starter-testtest com.github.pagehelper pagehelper-spring-boot-starter1.2.3 org.springframework.boot spring-boot-maven-plugin
2.application.xml配置。我的*maper.xml都是放在resource文件夹里面的。这里有个 mapper-locations一定要配你项目的，不懂的看我的项目结构。PageHelper照着配置就行了。
server:
port: 8080
spring:
datasource:
name: test
url: jdbc:mysql://127.0.0.1:3306/simonsdb
username: root
password: root
driver-class-name: com.mysql.jdbc.Driver
mybatis:
mapper-locations: classpath:mapper
List> selectAll();
List selectPage();
}
2.*mapper.xml。namespace对应Java中的mapper类。id = "base_Column_List"，是你要查询的表里面的所有字段。记得username不要写成name.这个我踩过好多坑。运行的时候一直报mapper找不到对应的方法。原因是name会被识别为关键字！！不要取名sql或者java的关键字，不然你会哭的！！
id, username, password
3.service.java。getPageInfo方法是重点。PageHelper的核心代码就只有一句:
PageHelper.startPage(pageNum,pageSize);//开始分页
Liststudents = studentMapper.selectPage();//查询数据库返回数据
PageInfopageInfo = new PageInfo<>(students);//得到数据，里面还带有分页的各个参数
很简单是不是。接下来介绍一下pageInfo自带的分页参数:
pageNum=5, //查询的页数(第5页)
pageSize=3, //每页的大小
size=3,
startRow=13,
endRow=15,
total=22,//总数
pages=8, //总页数：22/3=8
list=Page{count=true, pageNum=5, pageSize=3, startRow=12, endRow=15, total=22, pages=8, reasonable=true, pageSizeZero=false},
prePage=4, //前一页
nextPage=6, //后一页
isFirstPage=false, //是否是第一页
isLastPage=false, //是否是最后一页
hasPreviousPage=true, //是否有上一页
hasNextPage=true, //是否有下一页
navigatePages=8, //导航总页数
navigateFirstPage=1, //导航第一页
navigateLastPage=8, //导航最后一页
navigatepageNums=[1, 2, 3, 4, 5, 6, 7, 8]//页数码
看完后，是不是一个很完美的插件(狗头)。相关的分页参数都是很齐全的。
service代码。这里我先用getInfo拿到PageInfo。再把相关的参数和list数据拿出来。返回给controller即可。
package com.simons.service;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.simons.entity.Student;
import com.simons.mapper.StudentMapper;
import com.simons.util.PageRequest;
import com.simons.util.PageResult;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
import java.util.Map;
@Service
public class StudentService{
@Autowired
private StudentMapper studentMapper;
public List> findAll() {
// List students =
List> map = studentMapper.selectAll();
return map;
}
public PageResult findPage(PageRequest pageRequest) {
PageInfo pageInfo = getPageInfo(pageRequest);
PageResult pageResult = new PageResult();
pageResult.setPageNum(pageInfo.getPageNum());
pageResult.setPageSize(pageInfo.getPageSize());
pageResult.setTotalPages(pageInfo.getPages());
pageResult.setContent(pageInfo.getList());
return pageResult;
}
public PageInfo getPageInfo(PageRequest pageRequest) {
int pageNum = pageRequest.getPageNum();
int pageSize = pageRequest.getPageSize();
PageHelper.startPage(pageNum,pageSize);//核心代码:pageHelper查询分页
List students = studentMapper.selectPage();
PageInfo pageInfo = new PageInfo<>(students);
return pageInfo;
}
}
4.controller层。findpage方法。查找分页的方案。因为分页往往带有查询参数。这边没写。
package com.simons.controller;
import com.simons.service.StudentService;
import com.simons.util.PageRequest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
import java.util.List;
import java.util.Map;
//@RestController
//@RequestMapping("/student")
@Controller
@RequestMapping(value = {"/student"})
public class StudentController {
@Autowired
private StudentService studentService;
@ResponseBody
@RequestMapping(value="/findAll")
public List> findAll() {
return studentService.findAll();
}
@ResponseBody
@RequestMapping(value = {"/findPage"})
public Object findPage(@RequestParam(name = "pageNum")String pageNum , @RequestParam(name = "pageSize") String pageSize) {
PageRequest pageQuery = new PageRequest();
pageQuery.setPageNum(Integer.parseInt(pageNum));
pageQuery.setPageSize(Integer.parseInt(pageSize));
return studentService.findPage(pageQuery);
}
// @PostMapping(value="/findPage")
// public Object findPage(@RequestBody PageRequest pageQuery) {
// return studentService.findPage(pageQuery);
// }
}
5.utils类。一个是pageRequest请求分页，一个是pageResult返回分页的实体类
package com.simons.util;
import java.util.List;
public class PageResult {
private int pageNum;
private int pageSize;
private long totalSize;
private int totalPages;
private List content;
public int getPageNum() {
return pageNum;
}
public void setPageNum(int pageNum) {
this.pageNum = pageNum;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public long getTotalSize() {
return totalSize;
}
public void setTotalSize(long totalSize) {
this.totalSize = totalSize;
}
public int getTotalPages() {
return totalPages;
}
public void setTotalPages(int totalPages) {
this.totalPages = totalPages;
}
public List getContent() {
return content;
}
public void setContent(List content) {
this.content = content;
}
}
package com.simons.util;
public class PageRequest {
private int pageNum;
private int pageSize;
public int getPageNum() {
return pageNum;
}
public void setPageNum(int pageNum) {
this.pageNum = pageNum;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
}
6.spring项目启动 application.java
package com.simons;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ComponentScan;
@SpringBootApplication
@MapperScan("com.simons.mapper")
//@ComponentScan(basePackages={"com.simons.*"})
public class SimonsStudioApplication {
public static void main(String[] args) {
SpringApplication.run(SimonsStudioApplication.class, args);
}
}
三、测试:
启动spring。输入测试地址:
http://localhost:8080/student/findPage?pageNum=5&pageSize=3
