PageHelper分页插件及相关案例介绍
pagehelper是一个分页插件,用来后端API进行分页处理,pagehelper只需要pageNum(当前页)和pageSize(页大小)就可以自动实现查询的分页数据.只对紧接着后续一条查询语句起作用.
项目运行成功后,查询语句之前加 PageHelper.startPage(pageNum, pageSize) 即可实现分页,PageHelper只对紧跟着的第一个SQL语句起作用.分页成功后,实际分会的结果list类型是Page<E> ,可使用 PageInfo<E> 进行封装,后文有相应源码.
pagehelper可以与前端datatables或pagination插件配合使用.前端具体插件具体怎么使用这里不再介绍.
1.maven中引入依赖
<!-- 分页插件 -->
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.2.3</version>
</dependency>
<!-- entity插件 -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.18</version>
</dependency>
2.controller
@GetMapping("/testresult/{project}/{pageNum}/{pagesize}")
public ResponseEntity<TestResultResponse>
getPhaseSmokeResult(@PathVariable(value="pageNum",defaultValue="1")Integer pageNum,
@PathVariable(value="pageSize",defaultValue="6")Integer pageSize,
@PathVariable("project")String project){
log.debug("REST request to get {} phase smoke result from {} to {} ", project, pageNum, pageSize);
TestResultResponse response = smokeResultService.getPhaseSmokeResult(pageNum,pagesize,project);
return new ResponseEntity<>(response, HttpStatus.OK);
}
3.serviceImpl
@Override
public TestResultResponse getPhaseSmokeResult(Integer pageNum, Integer pagesize, String project) {
PageHelper.startPage(pageNum, pagesize);
List<SmokeResult> smokeResultList = smokeResultMapper.getPhaseSmokeResult(project);
PageInfo<SmokeResult> pageInfo = new PageInfo<>(smokeResultList);
TestResultResponse response = new TestResultResponse();
response.setProject(project).setPageInfo(pageInfo);
return response;
}
4.entity
TestResultResponse类
@Data
@NoArgsConstructor
@AllArgsConstructor
@Accessors(chain = true)
public class TestResultResponse {
private String project;
private String version;
private String starttime;
private String endtime;
private String total;
private PageInfo pageInfo;
}
5.PageInfo源码
import com.github.pagehelper.Page;
import lombok.Data;
import java.io.Serializable;
import java.util.Collection;
import java.util.List;
@Data
public class PageInfo<T> implements Serializable{
private static final long serialVersionUID = 1L;
//当前页
private int pageNum;
//每页的数量
private int pageSize;
//当前页的数量
private int size;
//由于startRow和endRow不常用，这里说个具体的用法
//可以在页面中"显示startRow到endRow 共size条数据"
//当前页面第一个元素在数据库中的行号
private int startRow;
//当前页面最后一个元素在数据库中的行号
private int endRow;
//总记录数
private long total;
//总页数
private int pages;
//结果集
private List<T> list;
//前一页
private int prePage;
//下一页
private int nextPage;
//是否为第一页
private boolean isFirstPage = false;
//是否为最后一页
private boolean isLastPage = false;
//是否有前一页
private boolean hasPreviousPage = false;
//是否有下一页
private boolean hasNextPage = false;
//导航页码数,页码导航连续显示的页数
private int navigatePages;
//所有导航页号
private int[] navigatepageNums;
//导航条上的第一页
private int navigateFirstPage;
//导航条上的最后一页
private int navigateLastPage;
public PageInfo() {
}
/**
* 包装Page对象
*
* @param list
*/
public PageInfo(List<T> list) {
this(list, 8);
}
/**
* 包装Page对象
*
* @param list page结果
* @param navigatePages 页码数量,页码导航连续显示的页数
*/
public PageInfo(List<T> list, int navigatePages) {
if (list instanceof Page) {
Page page = (Page) list;
this.pageNum = page.getPageNum();
this.pageSize = page.getPageSize();
this.pages = page.getPages();
this.list = page;
this.size = page.size();
this.total = page.getTotal();
//由于结果是>startRow的，所以实际的需要+1
if (this.size == 0) {
this.startRow = 0;
this.endRow = 0;
} else {
this.startRow = page.getStartRow() + 1;
//计算实际的endRow（最后一页的时候特殊）
this.endRow = this.startRow - 1 + this.size;
}
} else if (list instanceof Collection) {
this.pageNum = 1;
this.pageSize = list.size();
this.pages = this.pageSize > 0 ? 1 : 0;
this.list = list;
this.size = list.size();
this.total = list.size();
this.startRow = 0;
this.endRow = list.size() > 0 ? list.size() - 1 : 0;
}
if (list instanceof Collection) {
this.navigatePages = navigatePages;
//计算导航页
calcNavigatepageNums();
//计算前后页，第一页，最后一页
calcPage();
//判断页面边界
judgePageBoudary();
}
}
/**
* 计算导航页
*/
private void calcNavigatepageNums() {
//当总页数小于或等于导航页码数时
if (pages <= navigatePages) {
navigatepageNums = new int[pages];
for (int i = 0; i < pages; i++) {
navigatepageNums[i] = i + 1;
}
} else { //当总页数大于导航页码数时
navigatepageNums = new int[navigatePages];
int startNum = pageNum - navigatePages / 2;
int endNum = pageNum + navigatePages / 2;
if (startNum < 1) {
startNum = 1;
//最前navigatePages页
for (int i = 0; i < navigatePages; i++) {
navigatepageNums[i] = startNum++;
}
} else if (endNum > pages) {
endNum = pages;
//最后navigatePages页
for (int i = navigatePages - 1; i >= 0; i--) {
navigatepageNums[i] = endNum--;
}
} else {
//所有中间页
for (int i = 0; i < navigatePages; i++) {
navigatepageNums[i] = startNum++;
}
}
}
}
/**
* 计算前后页，第一页，最后一页
*/
private void calcPage() {
if (navigatepageNums != null && navigatepageNums.length > 0) {
navigateFirstPage = navigatepageNums[0];
navigateLastPage = navigatepageNums[navigatepageNums.length - 1];
if (pageNum > 1) {
prePage = pageNum - 1;
}
if (pageNum < pages) {
nextPage = pageNum + 1;
}
}
}
/**
* 判定页面边界
*/
private void judgePageBoudary() {
isFirstPage = pageNum == 1;
// isLastPage = pageNum == pages;
isLastPage = pageNum == pages || pages == 0;
hasPreviousPage = pageNum > 1;
hasNextPage = pageNum < pages;
}
}
参考链接:
