Java多人导出Excel干崩服务器？排队导出功能实现方案

一、问题分析

多人同时导出Excel时，服务器资源（如CPU、内存、I/O）会被大量消耗，导致性能下降甚至崩溃。主要问题包括：

1. 资源消耗大：每次导出都需要从数据库中查询数据并进行格式化、计算等操作，这会大量消耗服务器资源。
2. 数据库压力大：大量并发请求会导致数据库查询变慢，甚至耗尽连接池。
3. 网络瓶颈：多个用户同时下载大文件会占用大量带宽。

二、解决方案

（一）实现排队导出功能

通过维护一个固定大小的导出队列，限制并发导出任务的数量，确保服务器资源的合理利用。

1. ExportQueue队列

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import java.util.LinkedList;

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

    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.printStackTrace();
            }
        }
        queue.add(sysUser);
        log.info("目前导出队列排队人数：" + queue.size());
        notifyAll();
        return queue;
    }

    public synchronized ExportUser getNextSysUser() {
        while (queue.isEmpty()) {
            try {
                wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        ExportUser sysUser = queue.remove();
        notifyAll();
        return sysUser;
    }
}

2. AbstractExport导出类

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;

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

    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);
            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);
}

3. ExportImpl导出实现方法

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) {
    }

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

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

4. 测试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.RequestBody;
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();
    }
}

三、总结

通过实现排队导出功能，可以有效限制并发导出任务的数量，避免服务器因资源耗尽而崩溃。这种方案不仅提高了系统的稳定性，还确保了导出任务的顺序执行。希望本文的示例和讲解对您有所帮助。