mybatis-pageHelper官网：https://github.com/pagehelper
本篇博文在上篇博文：SpringBoot使用Maven建立多模块工程(二)基础上继续更新。
【1】版本与配置文件
Springboot版本：2.1.0.RELEASE。在pom中添加mybatis-pageHelper配置如下：
<!--pagehelper自动依赖mybatis -->
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.2.10</version>
</dependency>
application.yml配置文件如下：
server:
port: 8081
# 配置mybatis
mybatis:
config-location: classpath:mybatis/mybatis-config.xml
mapper-locations: classpath*:mybatis/mapper/*.xml
pagehelper:
helperDialect: mysql
reasonable: true
supportMethodsArguments: true
params: count=countSql
spring:
datasource:
url: jdbc:mysql://localhost:3306/hhprovince?serverTimezone=GMT%2B8
username: root
password: 123456
driver-class-name: com.mysql.cj.jdbc.Driver
type: com.alibaba.druid.pool.DruidDataSource
initialSize: 50
maxActive: 200
maxWait: 60000
minIdle: 20
timeBetweenEvictionRunsMillis: 60000
minEvictableIdleTimeMillis: 300000
validationQuery: SELECT 1 FROM DUAL
testWhileIdle: true
testOnBorrow: true
testOnReturn: false
poolPreparedStatements: true
# 配置监控统计拦截的filters，去掉后监控界面sql无法统计，'wall'用于防火墙
filters: stat,wall,log4j
maxPoolPreparedStatementPerConnectionSize: 20
useGlobalDataSourceStat: true
connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=500
debug: true
logging:
level.com.github.pagehelper: debug
level.com.jane: debug
【2】添加Mapper类
SysApkMapper2如下所示，这里使用注解：
@Mapper
public interface SysApkMapper2 {
@Select("SELECT * FROM tb_sys_apk")
Page<SysApk> getSysApkList();
}
Page<SysAPk>是什么？其继承了ArrayList<E>，如下图所示：
添加了如下属性：
private static final long serialVersionUID = 1L;
private int pageNum;
private int pageSize;
private int startRow;
private int endRow;
private long total;
private int pages;
private boolean count;
private Boolean reasonable;
private Boolean pageSizeZero;
private String countColumn;
private String orderBy;
private boolean orderByOnly;
也就意味着，当你获取到了Page<SysAPk>后，你可以手动获取分页信息返回给前端需要的分页数据格式。当然，通常不会这么做，因为有一个PageInfo<T>来帮助我们处理。
【3】Controller中添加测试方法
testPageHelper方法如下：
@RequestMapping("/page")
public Object testPageHelper(){
PageHelper.startPage(1, 2,true);
Page<SysApk> sysApkList= apkMapper2.getSysApkList();
System.out.println("sysApkList : "+sysApkList);
PageInfo pageInfo = new PageInfo(sysApkList);
JSONObject jsonObject = new JSONObject();
jsonObject.put("pageInfo",pageInfo);
return jsonObject;
}PageInfo<T>是什么？
如下所示，其拥有分页相关属性并实现了序列号接口：
public class PageInfo<T> extends PageSerializable<T> {
private int pageNum;
private int pageSize;
private int size;
private int startRow;
private int endRow;
private int pages;
private int prePage;
private int nextPage;
private boolean isFirstPage;
private boolean isLastPage;
private boolean hasPreviousPage;
private boolean hasNextPage;
private int navigatePages;
private int[] navigatepageNums;
private int navigateFirstPage;
private int navigateLastPage;其构造方法如下所示：
public PageInfo() {
this.isFirstPage = false;
this.isLastPage = false;
this.hasPreviousPage = false;
this.hasNextPage = false;
}
public PageInfo(List<T> list) {
this(list, 8);
}
public PageInfo(List<T> list, int navigatePages) {
super(list);
this.isFirstPage = false;
this.isLastPage = false;
this.hasPreviousPage = false;
this.hasNextPage = false;
//判断list 是否为Page类型
if (list instanceof Page) {
Page page = (Page)list;
this.pageNum = page.getPageNum();
this.pageSize = page.getPageSize();
this.pages = page.getPages();
this.size = page.size();
if (this.size == 0) {
this.startRow = 0;
this.endRow = 0;
} else {
this.startRow = page.getStartRow() + 1;
this.endRow = this.startRow - 1 + this.size;
}
// list 为原生Collection类型
} else if (list instanceof Collection) {
this.pageNum = 1;
this.pageSize = list.size();
this.pages = this.pageSize > 0 ? 1 : 0;
this.size = list.size();
this.startRow = 0;
this.endRow = list.size() > 0 ? list.size() - 1 : 0;
}
if (list instanceof Collection) {
this.navigatePages = navigatePages;
this.calcNavigatepageNums();
this.calcPage();
this.judgePageBoudary();
}
}从上面可以看到，传给PageInfo<T>的list既可以是 Page<SysApk>也可以是List<SysApk>。
查看console：
可以发现进行了count统计和limit分页。
页面返回数据：
{
"pageInfo": {
"total": 3,
"list": [{
"id": 1,
"versionCode": 1,
"versionName": "1",
"versionMsg": "1",
"apkName": "1",
"downUrl": "1",
"createDate": "2019-03-19T01:19:12.000+0000",
"ifWork": 1,
"ifDelete": 0,
"ifForce": 0,
"memo": "111",
"phoneType": 1
}, {
"id": 2,
"versionCode": 2,
"versionName": "2",
"versionMsg": "2",
"apkName": "2",
"downUrl": "2",
"createDate": "2019-03-19T01:19:50.000+0000",
"ifWork": 1,
"ifDelete": 0,
"ifForce": 0,
"memo": "222",
"phoneType": 2
}],
"pageNum": 1,
"pageSize": 2,
"size": 2,
"startRow": 1,
"endRow": 2,
"pages": 2,
"prePage": 0,
"nextPage": 2,
"isFirstPage": true,
"isLastPage": false,
"hasPreviousPage": false,
"hasNextPage": true,
"navigatePages": 8,
"navigatepageNums": [1, 2],
"navigateFirstPage": 1,
"navigateLastPage": 2
}
}【4】startPage方法的几个参数
startPage方法源码如下：
public static <E> Page<E> startPage(int pageNum, int pageSize, boolean count, Boolean reasonable, Boolean pageSizeZero) {
Page<E> page = new Page(pageNum, pageSize, count);
page.setReasonable(reasonable);
page.setPageSizeZero(pageSizeZero);
Page<E> oldPage = getLocalPage();
if (oldPage != null && oldPage.isOrderByOnly()) {
page.setOrderBy(oldPage.getOrderBy());
}
setLocalPage(page);
return page;
}count为true时将会进行count统计，为false时不会进行count统计。
此时返回的信息为：
{
"pageInfo": {
"total": -1,
"list": [{
"id": 1,
"versionCode": 1,
"versionName": "1",
"versionMsg": "1",
"apkName": "1",
"downUrl": "1",
"createDate": "2019-03-19T01:19:12.000+0000",
"ifWork": 1,
"ifDelete": 0,
"ifForce": 0,
"memo": "111",
"phoneType": 1
}, {
"id": 2,
"versionCode": 2,
"versionName": "2",
"versionMsg": "2",
"apkName": "2",
"downUrl": "2",
"createDate": "2019-03-19T01:19:50.000+0000",
"ifWork": 1,
"ifDelete": 0,
"ifForce": 0,
"memo": "222",
"phoneType": 2
}],
"pageNum": 1,
"pageSize": 2,
"size": 2,
"startRow": 1,
"endRow": 2,
"pages": 1,
"prePage": 0,
"nextPage": 0,
"isFirstPage": true,
"isLastPage": true,
"hasPreviousPage": false,
"hasNextPage": false,
"navigatePages": 8,
"navigatepageNums": [1],
"navigateFirstPage": 1,
"navigateLastPage": 1
}
}pageSizeZero：默认值为 false，当该参数设置为 true 时，如果 pageSize=0 或者 RowBounds.limit = 0 就会查询出全部的结果（相当于没有执行分页查询，但是返回结果仍然是 Page 类型）。
reasonable：分页合理化参数，默认值为false。当该参数设置为 true 时，pageNum<=0 时会查询第一页， pageNum>pages（超过总数时），会查询最后一页。默认false 时，直接根据参数进行查询。
更多参数详情参看官网：mybatis-pageHelper-DOC
