# EasyExcel — Fast Memory-Efficient Excel Processing for Java

> Alibaba's open-source Java library for reading and writing large Excel files without running out of memory. Handles millions of rows with minimal heap usage through streaming and event-driven parsing.

## Install

Save in your project root:

# EasyExcel — Fast Memory-Efficient Excel Processing for Java

## Quick Use
```xml
<!-- Maven dependency -->
<dependency>
  <groupId>com.alibaba</groupId>
  <artifactId>easyexcel</artifactId>
  <version>4.0.3</version>
</dependency>
```
```java
// Read an Excel file
EasyExcel.read("input.xlsx", DataModel.class, new DataListener()).sheet().doRead();
// Write an Excel file
EasyExcel.write("output.xlsx", DataModel.class).sheet("Sheet1").doWrite(dataList);
```

## Introduction
EasyExcel is a Java library by Alibaba designed to solve the memory overflow problems that plague Apache POI when handling large spreadsheets. It uses an event-driven SAX-style parser for reads and a streaming writer for exports, keeping memory usage flat regardless of file size.

## What EasyExcel Does
- Reads Excel files (xls and xlsx) with constant memory consumption via streaming
- Writes large datasets to Excel with automatic sheet splitting and style support
- Maps Excel columns to Java objects through annotations for type-safe parsing
- Supports custom converters, validators, and listeners for complex data pipelines
- Handles merged cells, formulas, images, and multi-sheet workbooks

## Architecture Overview
EasyExcel wraps Apache POI's low-level SAX event reader for xlsx and the legacy HSSFEventFactory for xls, exposing a high-level annotation-based API. During reads, rows stream through a listener callback one at a time so only a small window of data resides in memory. Writes use a streaming workbook that flushes rows to disk in batches. A reflection-based converter layer automatically maps between Excel cells and annotated Java fields.

## Self-Hosting & Configuration
- Add the Maven or Gradle dependency to your project — no external services required
- Annotate Java model classes with @ExcelProperty to map columns by name or index
- Implement a ReadListener to process rows as they stream in from the file
- Configure write styles, column widths, and merge strategies via builder methods
- Use the fill template feature to populate pre-designed Excel templates with data

## Key Features
- Reads a 750,000-row file using roughly 64 MB of heap versus multiple GB with POI
- Annotation-driven column mapping eliminates manual cell-index bookkeeping
- Built-in support for Excel template filling for report generation
- Automatic type conversion between Java types and Excel cell formats
- Compatible with both legacy .xls and modern .xlsx file formats

## Comparison with Similar Tools
- **Apache POI** — the standard Java Excel library but loads entire workbooks into memory; EasyExcel wraps POI's SAX layer for constant-memory streaming
- **JExcelApi** — lightweight xls-only library; lacks xlsx support and is no longer maintained
- **Alibaba DataX** — a data synchronization tool, not an Excel library; complementary rather than competing
- **OpenCSV** — handles CSV files only; EasyExcel covers the full xlsx/xls format including styles and formulas
- **Python openpyxl / pandas** — popular in the Python ecosystem; EasyExcel serves the same role for Java and Spring Boot projects

## FAQ
**Q: How much memory does EasyExcel use for large files?**
A: EasyExcel processes rows one at a time via streaming, so heap usage stays constant (typically 64-128 MB) regardless of file size.

**Q: Can I use EasyExcel with Spring Boot?**
A: Yes. It is a plain Java library that works in any Spring Boot project. Many teams use it for REST endpoints that export reports.

**Q: Does EasyExcel support writing styled Excel files?**
A: Yes. You can apply cell styles, fonts, colors, column widths, and merged regions through the write builder API.

**Q: Is EasyExcel actively maintained?**
A: Yes. Alibaba continues to release updates and the project has an active community on GitHub.

## Sources
- https://github.com/alibaba/easyexcel
- https://easyexcel.opensource.alibaba.com/

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Source: https://tokrepo.com/en/workflows/asset-e42b53dc
Author: AI Open Source