Java zip批量下载和踩坑笔记

话不多说，直接上代码
需求是 阿里云 url pfd 文件打包成zip
代码如下

import com.google.common.collect.Lists;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.StopWatch;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import java.util.zip.GZIPOutputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
/**
 * 下载工具类.
 * @author  <a href="huangxy@smartebao.com">huang__2</a>
 * @version $Id: DownLoadTool.java  2021/1/19 1:44 下午  huangxy $
 * @since 2.0
 */
public class DownLoadTool {

    /**
     * logger.
     */
    private static Logger log = LoggerFactory.getLogger(DownLoadTool.class);

    /**
     * 线程池.
     */
    RejectedExecutionHandler handler = new ThreadPoolExecutor.CallerRunsPolicy();
    private ThreadPoolExecutor executor = new ThreadPoolExecutor(4,
            20,
            30, TimeUnit.SECONDS,
            new LinkedBlockingDeque<>(4),
            new ThreadFactoryBuilder().setNameFormat("pdf-threadPool-%d").build(),
            handler);

    private static DownLoadTool instance = new DownLoadTool();

    private DownLoadTool() {
    }

    /**
     * @return the instance
     */
    public static DownLoadTool getInstance() {
        return instance;
    }


    /**
     * 下载节点.
     */
    class DownloadNode {
        String fileName;
        InputStream in;

        public DownloadNode(String fileName, InputStream in) {
            this.fileName = fileName;
            this.in = in;
        }

        /**
         * @return the fileName
         */
        public String getFileName() {
            return fileName;
        }

        /**
         * @return the in
         */
        public InputStream getIn() {
            return in;
        }
    }
 private void packageResponse(HttpServletRequest request, HttpServletResponse response, String zipName) throws UnsupportedEncodingException {
        response.setHeader("content-type", "application/octet-stream");
        response.setCharacterEncoding("utf-8");
        final String userAgent = request.getHeader("user-agent");
        boolean flag = null != userAgent && (userAgent.indexOf("Firefox") >= 0
                || userAgent.indexOf("Chrome") >= 0 || userAgent.indexOf("Safari") >= 0);
        if (flag) {
            zipName = new String(zipName.getBytes(), "ISO8859-1");
        } else {
            zipName = URLEncoder.encode(zipName, "UTF8");
        }
        response.setHeader("Content-disposition",
                "attachment;filename=" + new String(zipName.getBytes("gbk"), "iso8859-1"));
    }

	// 多线程打包下载
    public void downloadZipByMultiThread(HttpServletResponse response, Map<String, String> urlName, String zipName) {
        StopWatch sw = new StopWatch("downloadZipByMultiThead");
        sw.start("task2");
        OutputStream out = null;
        ZipOutputStream zos = null;
        try {
            out = response.getOutputStream();
            response.reset();
            // 设定输出文件头
            response.setHeader("Content-Disposition", "attachment;fileName="
                    + new String(zipName.getBytes("utf-8"), "iso8859-1"));
            response.setContentType("application/zip");
            zos = new ZipOutputStream(out);
            List<DownloadNode> downloadNodes = Collections.synchronizedList(Lists.newArrayListWithCapacity(urlName.size()));
            CompletableFuture[] futures = urlName.entrySet()
                    .stream()
                    .map(entry -> CompletableFuture.runAsync(() -> downloadNodes.add(new DownloadNode(entry.getValue(), getIn(entry.getKey()))), executor))
                    .toArray(size -> new CompletableFuture[size]);
            CompletableFuture.allOf(futures).get(5, TimeUnit.SECONDS);
            for (DownloadNode node : downloadNodes) {
                writeZipEntry(zos, node);
            }
            sw.stop();
            System.out.println(sw.prettyPrint());
        } catch (Exception e) {
            log.error("下载失败", e);
        } finally {
            if (zos != null) {
                try {
                    zos.flush();
                    zos.close();
                } catch (IOException e) {
                    log.error("zos 异常", e);
                }
            }

            if (out != null) {
                try {
                    out.flush();
                    out.close();
                } catch (IOException e) {
                    log.error("out 异常", e);
                }
            }
        }


    }

    private void writeZipEntry(ZipOutputStream zos, DownloadNode downloadNode) {
        try {
            byte[] buf = new byte[8192];
            int len;
            InputStream in = downloadNode.getIn();
            ZipEntry ze = new ZipEntry(downloadNode.getFileName() + ".pdf");
            zos.putNextEntry(ze);
            BufferedInputStream bis = new BufferedInputStream(in);
            while ((len = bis.read(buf)) != -1) {
                zos.write(buf, 0, len);
            }
            bis.close();
            zos.closeEntry();
        } catch (IOException e) {
            log.error("io 异常", e);
        }

    }


    /**
     * 压缩文件 打包 pdf
     *
     * @param response response
     * @param urlName  key -> url  , value  -> fileName
     * @param zipName  打包名字
     */
    public void downloadZip(HttpServletResponse response, Map<String, String> urlName, String zipName) {
        OutputStream out = null;
        ZipOutputStream zos = null;
        byte[] buf = new byte[8192];
        int len = 0;
        try {
            out = response.getOutputStream();
            response.reset();
            // 设定输出文件头
            response.setHeader("Content-Disposition", "attachment;fileName="
                    + new String(zipName.getBytes("utf-8"), "iso8859-1"));
            response.setContentType("application/zip");
            zos = new ZipOutputStream(out);

            for (Map.Entry<String, String> entry : urlName.entrySet()) {
                InputStream in = getIn(entry.getKey());
                ZipEntry ze = new ZipEntry(entry.getValue() + ".pdf");
                zos.putNextEntry(ze);
                BufferedInputStream bis = new BufferedInputStream(in);
                while ((len = bis.read(buf)) != -1) {
                    zos.write(buf, 0, len);
                }
                bis.close();
                zos.closeEntry();
            }
        } catch (Exception e) {
            log.error("下载失败", e);
        } finally {
            // 流关闭的顺序很重要。
            if (zos != null) {
                try {
                    zos.flush();
                    zos.close();
                } catch (IOException e) {
                    log.error("zos 异常", e);
                }
            }
            if (out != null) {
                try {
                    out.flush();
                    out.close();
                } catch (IOException e) {
                    log.error("out 异常", e);
                }
            }
        }
    }

    /**
     * 通过 url 打开 一个io 流
     *
     * @param src 阿里云url 地址
     * @return InputStream
     */
    private static InputStream getIn(String src) {
        if (StringUtils.isEmpty(src)) {
            return null;
        }
        InputStream in = null;
        try {
            URL url = new URL(src);
            HttpURLConnection httpUrl = (HttpURLConnection) url.openConnection();
            httpUrl.connect();
            in = httpUrl.getInputStream();
            return in;
        } catch (IOException e) {
            log.error("读取url数据失败", e);
        }
        return null;
    }
}

踩坑

1. 流关闭的顺序很重要。不然你会发现 zip 包打不开。

    if(zos != null) {
                try {
                    zos.flush();
                    zos.close();
                } catch (IOException e) {
                    //e.printStackTrace();
                }
            }
            if(out != null) {
                try {
                    out.flush();
                    out.close();
                } catch (IOException e) {
                    //e.printStackTrace();
                }
            }