POI's SXSSFWorkbook large amounts of data export to excel on memory overflow

One: Introduction

      SXSSFWorkbook是用来生成海量excel数据文件，主要原理是借助临时存储空间生成excel，
      SXSSFWorkbook专门处理大数据，对于大型excel的创建且不会内存溢出的，就只有SXSSFWorkbook了。
      它的原理很简单，用硬盘空间换内存（就像hashmap用空间换时间一样）。 SXSSFWorkbook是streaming
      版本的XSSFWorkbook,它只会保存最新的excel rows在内存里供查看，在此之前的excel rows都会被写入到
      硬盘里（Windows电脑的话，是写入到C盘根目录下的temp文件夹）。被写入到硬盘里的rows是不可见的/不
      可访问的。只有还保存在内存里的才可以被访问到。 
      注:HSSFWorkbook和XSSFWorkbook的Excel Sheet导出条数上限(<=2003版)是65535行、256列,(>=2007版)
           是1048576行,16384列,如果数据量超过了此上限,那么可以使用SXSSFWorkbook来导出。实际上上万条数据，
           甚至上千条数据就可以考虑使用SXSSFWorkbook了。
    注意：首先需要引入依赖：注意：4.0.0版本的JDK需要1.8以上，如果JDK是1.7的，那么就使用3.9版本的依赖

	<!-- https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml-schemas -->
		<dependency>
		    <groupId>org.apache.poi</groupId>
		    <artifactId>poi-ooxml-schemas</artifactId>
		    <version>4.0.0</version>
		</dependency>
		<!-- https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml -->
		<dependency>
		    <groupId>org.apache.poi</groupId>
		    <artifactId>poi-ooxml</artifactId>
		    <version>4.0.0</version>
		</dependency>
		<!-- https://mvnrepository.com/artifact/org.apache.poi/poi -->
		<dependency>
		    <groupId>org.apache.poi</groupId>
		    <artifactId>poi</artifactId>
		    <version>4.0.0</version>
		</dependency>

II: Example one, we use SXSSFWorkbook write data to Excel 500 000, you need only about 34 seconds, and memory usage up to about 700M, CPU utilization at around 25%

package com.test.POI;
 
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
 
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.xssf.streaming.SXSSFRow;
import org.apache.poi.xssf.streaming.SXSSFSheet;
import org.apache.poi.xssf.streaming.SXSSFWorkbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
 
public class SXSSFWORKBookUtils {
 
	@SuppressWarnings("resource")
	public static void main(String[] args) throws FileNotFoundException, InvalidFormatException {
		long startTime = System.currentTimeMillis();
		String filePath = "E:\\txt\\111.xlsx";
		SXSSFWorkbook sxssfWorkbook = null;
		BufferedOutputStream outputStream = null;
		try {
			//这样表示SXSSFWorkbook只会保留100条数据在内存中，其它的数据都会写到磁盘里，这样的话占用的内存就会很少
			 sxssfWorkbook = new SXSSFWorkbook(getXSSFWorkbook(filePath),100);
			 //获取第一个Sheet页
			 SXSSFSheet sheet = sxssfWorkbook.getSheetAt(0);
			 for (int i = 0; i < 50; i++) {
				 for (int z = 0; z < 10000; z++) {
					 SXSSFRow row = sheet.createRow(i*10000+z);
					 for (int j = 0; j < 10; j++) {
						 row.createCell(j).setCellValue("你好："+j);
					 }
				 }
			}
			 outputStream = new BufferedOutputStream(new FileOutputStream(filePath));
			 sxssfWorkbook.write(outputStream);
			 outputStream.flush();
			 sxssfWorkbook.dispose();// 释放workbook所占用的所有windows资源
		} catch (IOException e) {
			e.printStackTrace();
		}finally {
			if(outputStream!=null) {
				try {
					outputStream.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		long endTime = System.currentTimeMillis();
		System.out.println(endTime-startTime);
	}
	
	
	/**
	 * 先创建一个XSSFWorkbook对象
	 * @param filePath
	 * @return
	 */
	public static XSSFWorkbook getXSSFWorkbook(String filePath) {
		XSSFWorkbook workbook =  null;
		BufferedOutputStream outputStream = null;
		try {
			File fileXlsxPath = new File(filePath);
			outputStream = new BufferedOutputStream(new FileOutputStream(fileXlsxPath));
			workbook = new XSSFWorkbook();
			workbook.createSheet("测试Sheet");
			workbook.write(outputStream);
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			if(outputStream!=null) {
				try {
					outputStream.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		return workbook;
	}
	
}

Effect:

Three: We used conventional methods XSSFWorkbook 500,000 simultaneous writing data to excel, the memory occupancy rate up to about 2.1 G (takes up a lot of memory), CPU utilization at around 90%, the last memory overflow

package com.test;
 
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
 
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
 
public class POIController {
	/**
	 * 这种方式效率比较低并且特别占用内存，数据量越大越明显
	 * @param args
	 * @throws FileNotFoundException
	 * @throws InvalidFormatException
	 */
	public static void main(String[] args) throws FileNotFoundException, InvalidFormatException {
		long startTime = System.currentTimeMillis();
		BufferedOutputStream outPutStream = null;
		XSSFWorkbook workbook = null;
		FileInputStream inputStream = null;
		String filePath = "E:\\txt\\666.xlsx";
		try {
			 workbook = getWorkBook(filePath);
			 XSSFSheet sheet = workbook.getSheetAt(0);
			 for (int i = 0; i < 50; i++) {
				 for (int z = 0; z < 10000; z++) {
					 XSSFRow row = sheet.createRow(i*10000+z);
					 for (int j = 0; j < 10; j++) {
						 row.createCell(j).setCellValue("你好："+j);
					 }
				 }
				 //每次要获取新的文件流对象，避免将之前写入的数据覆盖掉
				 outPutStream = new BufferedOutputStream(new FileOutputStream(filePath));
				 workbook.write(outPutStream);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}finally {
			if(outPutStream!=null) {
				try {
					outPutStream.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			if(inputStream!=null) {
				try {
					inputStream.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			if(workbook!=null) {
				try {
					workbook.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		long endTime = System.currentTimeMillis();
		System.out.println(endTime-startTime);
	}
	/**
	 * 先创建一个XSSFWorkbook对象
	 * @param filePath
	 * @return
	 */
	public static XSSFWorkbook getWorkBook(String filePath) {
		XSSFWorkbook workbook =  null;
		try {
			File fileXlsxPath = new File(filePath);
			BufferedOutputStream outPutStream = new BufferedOutputStream(new FileOutputStream(fileXlsxPath));
			workbook = new XSSFWorkbook();
			workbook.createSheet("测试");
			workbook.write(outPutStream);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return workbook;
	}
	
}

effect: