SpringBoot 引入分页插件 PageHelper_springboot配置pagehelper

官网

https://pagehelper.github.io/docs/howtouse/

引入步骤

第1步：引入依赖

<!--分页插件-->
<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper</artifactId>
    <version>5.3.2</version>
</dependency>
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第2步：配置拦截器插件

@Configuration
public class AppConfig {

    @Bean
    public PageInterceptor pageInterceptor() {
        PageInterceptor pageInterceptor = new PageInterceptor();
        Properties properties = new Properties();
        // 分页合理化，true开启，如果分页参数不合理会自动修正。默认false不启用
        properties.setProperty("reasonable", "true");
        pageInterceptor.setProperties(properties);
        return pageInterceptor;
    }

}
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[Ref] 整合PageHelper实现分页

第3步：插件的使用

前提：业务提供 查询所有学生的方法

// com.zhangziwa.practisesvr.mapper.UserMapper#listStudents
<select id="listStudents" resultMap="StudentMap">
    SELECT * FROM students
</select>

// com.zhangziwa.practisesvr.mapper.UserMapper
List<Student> listStudents();
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不使用分页插件 会查出全部

List<Student> students = userMapper.listStudents();
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分页查询 方式1：PageInfo

public List<Student> listStudents2(Integer pageNum, Integer PageSize) {
	PageHelper.startPage(1, 10, true);
    PageHelper.orderBy("age asc");
    
	List<Student> students = userMapper.listStudents();
	PageInfo<Student> studentPageInfo = PageInfo.of(students);
    return students;
}
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分页查询方式2：Page

public List<Student> listStudents2(Integer pageNum, Integer PageSize) {
	PageHelper.startPage(1, 10, true);
    PageHelper.orderBy("age asc");
    
    Page<Student> students = (Page<Student>) userMapper.listStudents();
    return students;
}
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分页查询方式3：多数据源聚合时的手工分页

public List<Student> listStudents3(Integer pageNum, Integer pageSize) {
	    // 模拟数据聚合
    List<Student> students3 = new ArrayList<>();
    List<Student> students1 = userMapper.listStudents();
    List<Student> students2 = userMapper.listStudents();
    
    students3.addAll(students1);
    students3.addAll(students2);
    
    Page<Student> studentsPage = PageHeaderUtils.manualPage(students3, pageNum, pageSize);
    return studentsPage;
}
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// 数据聚合场景下的手工分页
// 也适合EmptyList场景 Page{count=true, pageNum=1, pageSize=10, startRow=0, endRow=0, total=0, pages=0, reasonable=null, pageSizeZero=null}
public static <E> Page<E> manualPage(List<E> res, Integer pageNum, Integer pageSize) {
    if (res == null) {
        res = new ArrayList<>();
    }
    
    int pageNumber = PageUtils.getPageNum(pageNum);
    int sizePerPage = PageUtils.getPageSize(pageSize);
    int totalSize = res.size();
    
    List<E> pageElements = res.stream().skip((long) (pageNumber - 1) * sizePerPage).limit(sizePerPage).toList(); // 分页
    
    Page<E> page = new Page<>();
    page.setPageNum(pageNumber);
    page.setPageSize(sizePerPage);
    page.setTotal(totalSize);
    page.setPages((totalSize / pageSize + ((totalSize % pageSize == 0) ? 0 : 1)));
    page.addAll(pageElements);
    
    return page;
}
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常见问题

[Q&A] 在系统中发现了多个分页插件