alibaba/easyexcel

EasyExcel is a Java library from Alibaba designed to read and write Excel files quickly and without running out of memory, even when those files are very large. Traditional Java libraries for Excel, such as Apache POI, load the entire spreadsheet into RAM at once, which causes crashes or extreme slowness when files contain hundreds of thousands of rows. EasyExcel solves this by processing Excel files row-by-row in a streaming fashion, keeping memory usage minimal regardless of file size. According to the README, it can read a 75 MB Excel file with 460,000 rows using only about 16 MB of memory in roughly 23 seconds. The library works by letting you define a plain Java class that maps to a row of your spreadsheet, each field corresponds to a column. You then pass that class and a listener (a piece of code that gets called once per row) to EasyExcel, and it handles the rest. Writing works the same way in reverse: you provide a list of objects and EasyExcel produces the file. It supports both the older .xls format and the modern .xlsx format. Someone would use EasyExcel in a Java backend application that needs to import bulk data uploaded by users, export large reports, or handle batch data processing pipelines that involve spreadsheets. It is especially useful in enterprise systems where data exports can easily reach millions of rows. The README notes the project is entering maintenance mode, with bug fixes continuing but no new features planned. The tech stack is Java, distributed as a Maven dependency. Note: the README is primarily written in Chinese.