分页PageInterceptor

Moooooo / 2023-09-01 / 原文

依赖引入

<dependency>
    <groupId>com.github.pagehelper</groupId>
    <artifactId>pagehelper</artifactId>
    <version>xx.xx.xx</version>
</dependency>

编码

PageHelper.startPage()在查询前执行，设置Page放入ThreadLocal中

　　/com/github/pagehelper/page/PageMethod.java:147

PageInterceptor拦截请求，自动添加limit & offset

　　/com/github/pagehelper/util/ExecutorUtil.java:166

/com/github/pagehelper/PageInterceptor.java:140，count计数

private Long count(Executor executor, MappedStatement ms, Object parameter,
                       RowBounds rowBounds, ResultHandler resultHandler,
                       BoundSql boundSql) throws SQLException {
        String countMsId = countMsIdGen.genCountMsId(ms, parameter, boundSql, countSuffix);
        Long count;
        //先判断是否存在手写的 count 查询
        MappedStatement countMs = ExecutorUtil.getExistedMappedStatement(ms.getConfiguration(), countMsId);
        if (countMs != null) {
            count = ExecutorUtil.executeManualCount(executor, countMs, parameter, boundSql, resultHandler);
        } else {
            if (msCountMap != null) {
                countMs = msCountMap.get(countMsId);
            }
            //自动创建
            if (countMs == null) {
                //根据当前的 ms 创建一个返回值为 Long 类型的 ms
                countMs = MSUtils.newCountMappedStatement(ms, countMsId);
                if (msCountMap != null) {
                    msCountMap.put(countMsId, countMs);
                }
            }
            count = ExecutorUtil.executeAutoCount(this.dialect, executor, countMs, parameter, boundSql, rowBounds, resultHandler);
        }
        return count;
    }

@Bean
public PageInterceptor pageInterceptor(){
    return new PageInterceptor();
}

@GetMapping("/geta")
private PageInfo<Demo> getA(@RequestParam String str) {
    PageHelper.startPage(1, 3);
    List<Demo> querydemo = demoBaseMapper.querydemo(str);
    PageInfo<Demo> pageInfo = new PageInfo<Demo>(querydemo);
    return pageInfo;
}

{
    "total": 2,
    "list": [
        {
            "id": 1,
            "name": "tom",
            "date": "2023-08-28T16:00:00.000+00:00"
        }
    ],
    "pageNum": 1,
    "pageSize": 3,
    "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
}