ibatis 分页.docVIP

IBatis的分页研究 本文是在参阅了/blog/24739基础上完成的 在看JPetStore的代码时，发现它的分页处理主要是通过返回PaginatedList对象来完成的。如：在CatalogService类中 public?PaginatedList?getProductListByCategory(String?categoryId)?{?????return?productDao.getProductListByCategory(categoryId);???}? 分页是操作数据库型系统常遇到的问题。分页实现方法很多，但效率的差异就很大了。iBatis是通过什么方式来实现这个分页的了。查看它的实现部分： ? 返回的PaginatedList实际上是个接口，实现这个接口的是PaginatedDataList类的对象，查看PaginatedDataList类发现，每次翻页的时候最后都会调用下面这段函数 private?List?getList(int?idx,?int?localPageSize)?throws?SQLException?{?????return?sqlMapExecutor.queryForList(statementName,?parameterObject,?(idx)?*?pageSize,?localPageSize);???}? 由于 public?interface?SqlMapClient?extends?SqlMapExecutor,?SqlMapTransactionManager?{……}? 所以实际的调用次序如下： SqlMapClientImpl.queryForPaginatedList-SqlMapSessionImpl.queryForPaginatedList?-SqlMapExecutorDelegate.queryForPaginatedList-GeneralStatement.executeQueryForList?-GeneralStatment.executeQueryWithCallback-GeneralStatment.executeQueryWithCallback?-SqlExecutor.executeQuery-SqlExecutor.handleMultipleResults()-SqlExecutor.executeQuery-?handleResults? 分页处理的函数如下 private?void?handleResults(RequestScope?request,?ResultSet?rs,?int?skipResults,?int?maxResults,?RowHandlerCallback?callback)?throws?SQLException?{?????try?{???????request.setResultSet(rs);???????ResultMap?resultMap?=?request.getResultMap();???????if?(resultMap?!=?null)?{?????????//?Skip?Results?????????if?(rs.getType()?!=?ResultSet.TYPE_FORWARD_ONLY)?{???????????if?(skipResults??0)?{?????????????rs.absolute(skipResults);???????????}?????????}?else?{???????????for?(int?i?=?0;?i??skipResults;?i++)?{?????????????if?(!rs.next())?{???????????????return;?????????????}???????????}?????????}???????????//?Get?Results?????????int?resultsFetched?=?0;?????????while?((maxResults?==?SqlExecutor.NO_MAXIMUM_RESULTS?||?resultsFetched??maxResults)??rs.next())?{???????????Object[]?columnValues?=?resultMap.resolveSubMap(request,?rs).getResults(request,?rs);???????????callback.handleResultObject(request,?columnValu