<!-- EasyPOI 核心庫 -->
<dependency>
    <groupId>cn.afterturn</groupId>
    <artifactId>easypoi-spring-boot-starter</artifactId>
    <version>4.4.0</version>
</dependency>

<!-- Apache POI (SXSSF 需要) -->
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>5.2.3</version>
</dependency>

import cn.afterturn.easypoi.excel.annotation.Excel;
import cn.afterturn.easypoi.excel.entity.params.ExcelExportEntity;
import org.apache.poi.xssf.streaming.SXSSFSheet;
import org.apache.poi.xssf.streaming.SXSSFWorkbook;

import java.io.FileOutputStream;
import java.lang.reflect.Field;
import java.util.*;
import java.util.stream.Collectors;

public class BatchExcelExporter<T> {

    private final SXSSFWorkbook workbook;
    private final Class<T> clazz;
    private final List<ExcelExportEntity> exportEntities = new ArrayList<>();
    private int currentRowIndex = 0;

    public BatchExcelExporter(Class<T> clazz) {
        this.clazz = clazz;
        this.workbook = new SXSSFWorkbook(100); // 緩存100行到磁盤
        initHeader();
    }

    // 初始化表頭（僅執(zhí)行一次）
    private void initHeader() {
        // 解析實體類注解
        List<Field> fields = Arrays.stream(clazz.getDeclaredFields())
                .filter(f -> f.isAnnotationPresent(Excel.class))
                .sorted(Comparator.comparing(f -> {
                    Excel excel = f.getAnnotation(Excel.class);
                    return excel.orderNum();
                })).collect(Collectors.toList());

        // 構(gòu)建導出結(jié)構(gòu)
        fields.forEach(f -> {
            Excel excel = f.getAnnotation(Excel.class);
            exportEntities.add(new ExcelExportEntity(excel.name(), f.getName(), 4000));
        });

        // 創(chuàng)建表頭
        workbook.createSheet("數(shù)據(jù)").createRow(currentRowIndex++);
        addHeaderRow(workbook.getSheetAt(0).getRow(0));
    }

    // 添加表頭行
    private void addHeaderRow(org.apache.poi.ss.usermodel.Row headerRow) {
        for (int i = 0; i < exportEntities.size(); i++) {
            headerRow.createCell(i).setCellValue(exportEntities.get(i).getName());
        }
    }

    // 批量添加數(shù)據(jù)（分頁調(diào)用）
    public void addBatchData(List<T> batchData) throws Exception {
        org.apache.poi.ss.usermodel.Sheet sheet = workbook.getSheetAt(0);
        for (T data : batchData) {
            org.apache.poi.ss.usermodel.Row row = sheet.createRow(currentRowIndex++);
            fillDataRow(row, data);
        }
        // 每500行刷新到磁盤（根據(jù)數(shù)據(jù)量調(diào)整）
        if (currentRowIndex % 500 == 0) {
            ((SXSSFSheet) sheet).flushRows(500);
        }
    }

    // 填充數(shù)據(jù)行（利用反射動態(tài)取值）
    private void fillDataRow(org.apache.poi.ss.usermodel.Row row, T data) throws Exception {
        for (int i = 0; i < exportEntities.size(); i++) {
            Field field = clazz.getDeclaredField((String) exportEntities.get(i).getKey());
            field.setAccessible(true);
            Object value = field.get(data);
            row.createCell(i).setCellValue(value != null ? value.toString() : "");
        }
    }

    // 最終寫入文件
    public void exportToFile(String filePath) throws Exception {
        try (FileOutputStream fos = new FileOutputStream(filePath)) {
            workbook.write(fos);
        } finally {
            workbook.dispose(); // 清理臨時文件
        }
    }
}

public class User {
    @Excel(name = "姓名", orderNum = "0")
    private String name;

    @Excel(name = "年齡", orderNum = "1")
    private Integer age;

    @Excel(name = "郵箱", orderNum = "2")
    private String email;

    // 省略Getter/Setter
}

public class ExcelExportDemo {
    public static void main(String[] args) throws Exception {
        // 初始化導出器（指定實體類）
        BatchExcelExporter<User> exporter = new BatchExcelExporter<>(User.class);

        // 模擬分頁查詢數(shù)據(jù)（假設每次查詢1000條）
        for (int page = 1; page <= 10; page++) {
            List<User> batchData = queryUsersByPage(page, 1000);
            exporter.addBatchData(batchData);
        }

        // 導出到文件
        exporter.exportToFile("user_export.xlsx");
    }

    private static List<User> queryUsersByPage(int page, int size) {
        // 模擬數(shù)據(jù)庫查詢（此處返回測試數(shù)據(jù)）
        List<User> users = new ArrayList<>();
        for (int i = 0; i < size; i++) {
            users.add(new User("User" + i, 20 + i, "user" + i + "@example.com"));
        }
        return users;
    }
}

List<Field> fields = Arrays.stream(clazz.getDeclaredFields())
        .filter(f -> f.isAnnotationPresent(Excel.class))
        .sorted(Comparator.comparing(f -> f.getAnnotation(Excel.class).orderNum()))
        .collect(Collectors.toList());

public void addBatchData(List<T> batchData) throws Exception {
    // ... 填充數(shù)據(jù) ...
    if (currentRowIndex % 500 == 0) {
        ((SXSSFSheet) sheet).flushRows(500);  // ?? 關鍵性能優(yōu)化點！
    }
}