pagehelper踩坑记之分页乱套问题解决

 com.github.pagehelperpagehelper-spring-boot-starter${pagehelper.version}

public Object getUsers(int pageNum, int pageSize) { PageHelper.startPage(pageNum, pageSize); List list = userMapper.selectAllWithPage(null); com.github.pagehelper.Page listWithPage = (com.github.pagehelper.Page) list; System.out.println("listCnt:" + listWithPage.getTotal()); return list; }

 select * from t_users 

// com.github.pagehelper.PageInterceptor#intercept @Override public Object intercept(Invocation invocation) throws Throwable { try { Object[] args = invocation.getArgs(); MappedStatement ms = (MappedStatement) args[0]; Object parameter = args[1]; RowBounds rowBounds = (RowBounds) args[2]; ResultHandler resultHandler = (ResultHandler) args[3]; Executor executor = (Executor) invocation.getTarget(); CacheKey cacheKey; BoundSql boundSql; //由于逻辑关系，只会进入一次 if (args.length == 4) { //4 个参数时 boundSql = ms.getBoundSql(parameter); cacheKey = executor.createCacheKey(ms, parameter, rowBounds, boundSql); } else { //6 个参数时 cacheKey = (CacheKey) args[4]; boundSql = (BoundSql) args[5]; } checkDialectExists(); List resultList; //调用方法判断是否需要进行分页，如果不需要，直接返回结果 if (!dialect.skip(ms, parameter, rowBounds)) { //判断是否需要进行 count 查询 if (dialect.beforeCount(ms, parameter, rowBounds)) { //查询总数 Long count = count(executor, ms, parameter, rowBounds, resultHandler, boundSql); //处理查询总数，返回 true 时继续分页查询，false 时直接返回 if (!dialect.afterCount(count, parameter, rowBounds)) { //当查询总数为 0 时，直接返回空的结果 return dialect.afterPage(new ArrayList(), parameter, rowBounds); } } resultList = ExecutorUtil.pageQuery(dialect, executor, ms, parameter, rowBounds, resultHandler, boundSql, cacheKey); } else { //rowBounds用参数值，不使用分页插件处理时，仍然支持默认的内存分页 resultList = executor.query(ms, parameter, rowBounds, resultHandler, cacheKey, boundSql); } return dialect.afterPage(resultList, parameter, rowBounds); } finally { if(dialect != null){ dialect.afterAll(); } } }

/** * 开始分页 * * @param pageNum  页码 * @param pageSize 每页显示数量 * @param count    是否进行count查询 */ public static  Page startPage(int pageNum, int pageSize, boolean count) { return startPage(pageNum, pageSize, count, null, null); } /** * 开始分页 * * @param pageNum      页码 * @param pageSize     每页显示数量 * @param count        是否进行count查询 * @param reasonable   分页合理化,null时用默认配置 * @param pageSizeZero true且pageSize=0时返回全部结果，false时分页,null时用默认配置 */ public static  Page startPage(int pageNum, int pageSize, boolean count, Boolean reasonable, Boolean pageSizeZero) { Page page = new Page(pageNum, pageSize, count); page.setReasonable(reasonable); page.setPageSizeZero(pageSizeZero); //当已经执行过orderBy的时候 Page oldPage = getLocalPage(); if (oldPage != null && oldPage.isOrderByOnly()) { page.setOrderBy(oldPage.getOrderBy()); } setLocalPage(page); return page; } protected static final ThreadLocal LOCAL_PAGE = new ThreadLocal(); /** * 设置 Page 参数 * * @param page */ protected static void setLocalPage(Page page) { LOCAL_PAGE.set(page); } // com.github.pagehelper.PageHelper#afterAll @Override public void afterAll() { //这个方法即使不分页也会被执行，所以要判断 null AbstractHelperDialect delegate = autoDialect.getDelegate(); if (delegate != null) { delegate.afterAll(); autoDialect.clearDelegate(); } clearPage(); } /** * 移除本地变量 */ public static void clearPage() { LOCAL_PAGE.remove(); }

@RestController @RequestMapping("/hello") @Slf4j public class HelloController { @Resource private UserService userService; // 1. 先请求该getUsers接口，将得到异常，pageNum=1, pageSize=1 @GetMapping("getUsers") @ResponseBody public Object getUsers(int pageNum, int pageSize) { return userService.getUsers(pageNum, pageSize); } // 2. 多次请求该 getAllActors接口，正常情况下会得到N条全表记录，但将会偶发地得到只有一条记录，现象复现 @GetMapping("getAllActors") @ResponseBody public Object getAllActors() { return userService.getAllActors(); } } @Service @Slf4j public class UserService { @Resource private UserMapper userMapper; public Object getUsers(int pageNum, int pageSize) { PageHelper.startPage(pageNum, pageSize); // 此处强行抛出异常, 使以上 pagehelper 信息得以保存 throw new RuntimeException("exception ran"); } public Object getAllActors() { // 正常的全表查询 List list = userMapper.selectAllActors(); return list; } }