Implementing a FIFO Export Queue for Large Data Exports in Java

The business requirement is to handle growing database export volumes without degrading server performance; a fixed‑size FIFO queue is introduced to serialize export tasks, limiting concurrent MySQL I/O and file I/O.

Three main components are defined: ExportQueue for managing a bounded user queue, User information representing the export requester, and an Export class that performs the actual data export.

package com.example.system.config;

import com.example.system.api.domain.ExportUser;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import java.util.LinkedList;

@Slf4j
@Component
public class ExportQueue {
    private final int MAX_CAPACITY = 10; // 队列最大容量
    private LinkedList<ExportUser> queue; // 用户队列

    public ExportQueue(LinkedList<ExportUser> queue) {
        this.queue = new LinkedList<>();
    }

    /**
     * 排队队列添加
     * @param sysUser
     */
    public synchronized LinkedList<ExportUser> add(ExportUser sysUser) {
        while (queue.size() >= MAX_CAPACITY) {
            try {
                log.info("当前排队人已满，请等待");
                wait();
            } catch (InterruptedException e) {
                e.getMessage();
            }
        }
        queue.add(sysUser);
        log.info("目前导出队列排队人数：" + queue.size());
        notifyAll();
        return queue;
    }

    /**
     * 获取排队队列下一个人
     */
    public synchronized ExportUser getNextSysUser() {
        while (queue.isEmpty()) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        ExportUser sysUser = queue.remove();
        notifyAll(); // 唤醒
        return sysUser;
    }
}

The AbstractExport class defines a generic export framework using EasyExcel, handling pagination, file naming, and error handling while leaving data‑specific methods abstract.

package com.example.system.config;

import cn.hutool.core.bean.BeanUtil;
import cn.hutool.core.util.PageUtil;
import com.alibaba.excel.EasyExcel;
import com.alibaba.excel.ExcelWriter;
import com.alibaba.excel.write.metadata.WriteSheet;
import com.example.system.api.domain.ExportUser;
import lombok.extern.slf4j.Slf4j;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLEncoder;
import java.util.List;

@Slf4j
public abstract class AbstractExport<T, K> {
    public abstract void export(ExportUser sysUser) throws InterruptedException;

    /**
     * 导出
     */
    public void export(HttpServletResponse response, int pageSize, T t, Class<K> k, String fileName) throws Exception {
        ExcelWriter writer = null;
        try {
            writer = getExcelWriter(response, fileName);
            int total = this.countExport(t); // 查询导出总条数
            int loopCount = PageUtil.totalPage(total, pageSize);
            BeanUtil.setProperty(t, "pageSize", pageSize);
            for (int i = 0; i < loopCount; i++) {
                BeanUtil.setProperty(t, "pageNum", PageUtil.getStart(i + 1, pageSize));
                List<K> kList = this.getExportDetail(t);
                WriteSheet writeSheet = EasyExcel.writerSheet(fileName).head(k).build();
                writer.write(kList, writeSheet);
            }
        } catch (Exception e) {
            String msg = "导出" + fileName + "异常";
            log.error(msg, e);
            throw new Exception(msg + e);
        } finally {
            if (writer != null) {
                writer.finish();
            }
        }
    }

    public ExcelWriter getExcelWriter(HttpServletResponse response, String fileName) throws IOException {
        response.setContentType("application/vnd.ms-excel");
        response.setCharacterEncoding("utf-8");
        String fileNameUtf = URLEncoder.encode(fileName, "UTF-8").replaceAll("\\+", "%20");
        response.setHeader("Content-disposition", "attachment;filename*=utf-8''" + fileNameUtf + ".xlsx");
        return EasyExcel.write(response.getOutputStream()).build();
    }

    public abstract void complexFillWithTable(T t, String fileName, HttpServletResponse response);
    public abstract int countExport(T t);
    public abstract List<K> getExportDetail(T t);
}

The ExportImpl class extends AbstractExport, injects the ExportQueue, and implements the export logic, including simulated processing delay and queue management.

package com.example.system.service.impl;

import com.alibaba.excel.ExcelWriter;
import com.example.system.api.domain.ExportUser;
import com.example.system.config.AbstractExport;
import com.example.system.config.ExportQueue;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.LinkedList;
import java.util.List;

@Service
@Slf4j
public class ExportImpl extends AbstractExport {
    @Autowired
    private ExportQueue exportQueue;

    @Override
    public void export(ExportUser sysUser) throws InterruptedException {
        log.info("导出文件方法执行～～～～～～～～～");
        LinkedList<ExportUser> queue = exportQueue.add(sysUser);
        log.info("导出队列：" + queue);
        Thread.sleep(20000); // 模拟导出处理时间
        ExportUser nextSysUser = exportQueue.getNextSysUser();
        log.info("移除后获取下一个排队的用户: " + nextSysUser.getUserName());
    }

    @Override
    public void export(HttpServletResponse response, int pageSize, Object o, Class k, String fileName) throws Exception {
        super.export(response, pageSize, o, k, fileName);
    }

    @Override
    public ExcelWriter getExcelWriter(HttpServletResponse response, String fileName) throws IOException {
        return super.getExcelWriter(response, fileName);
    }

    @Override
    public void complexFillWithTable(Object o, String fileName, HttpServletResponse response) {
        // not implemented
    }

    @Override
    public int countExport(Object o) {
        return 0;
    }

    @Override
    public List getExportDetail(Object o) {
        return null;
    }
}

A simple ExportController demonstrates how multiple threads can invoke the export service, each creating an ExportUser and adding it to the queue.

package com.example.system.controller;

import com.example.system.api.domain.ExportUser;
import com.example.system.service.impl.ExportImpl;
import lombok.SneakyThrows;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/export")
@Slf4j
public class ExportController {
    @Autowired
    private ExportImpl export;

    @PostMapping("/exportFile")
    public void exportFile() {
        new Thread(new Runnable() {
            @SneakyThrows
            @Override
            public void run() {
                Thread thread1 = Thread.currentThread();
                ExportUser sysUser = new ExportUser();
                sysUser.setUserName(thread1.getName());
                export.export(sysUser);
            }
        }).start();
    }
}

Test results confirm that the queue enforces a maximum of ten concurrent export requests; when the limit is reached, additional requests wait until a slot becomes free, demonstrating proper FIFO behavior.

The article concludes with remarks about unfinished features (file table design, OSS upload, download, high‑concurrency considerations) and suggests that a Redis‑based queue could be an alternative implementation.