有時候在系統(tǒng)中需要一次性下載多個文件，但逐個下載文件比較麻煩。這時候，最好的解決辦法是將所有文件打包成一個壓縮文件，然后下載這個壓縮文件，這樣就可以一次性獲取所有所需的文件了。

下面是一個名為CompressUtil的工具類的代碼，它提供了一些方法來處理文件壓縮和下載操作：

import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.lucene.util.RamUsageEstimator;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.*;
import java.util.zip.*;

/**
 * @author fhey
 * @date 2023-05-11 20:48:28
 * @description: 壓縮工具類
 */

public class CompressUtil {

    private static final Logger logger = LoggerFactory.getLogger(CompressUtil.class);

    /**
     * 將文件打包到zip并創(chuàng)建文件
     *
     * @param sourceFilePath
     * @param zipFilePath
     * @throws IOException
     */
    public static void createLocalCompressFile(String sourceFilePath, String zipFilePath) throws IOException {
        createLocalCompressFile(sourceFilePath, zipFilePath, null);
    }

    /**
     * 將文件打包到zip并創(chuàng)建文件
     *
     * @param sourceFilePath
     * @param zipFilePath
     * @param zipName
     * @throws IOException
     */
    public static void createLocalCompressFile(String sourceFilePath, String zipFilePath, String zipName) throws IOException {
        File sourceFile = new File(sourceFilePath);
        if (!sourceFile.exists()) {
            throw new RuntimeException(sourceFilePath + "不存在！");
        }
        if(StringUtils.isBlank(zipName)){
            zipName = sourceFile.getName();
        }
        File zipFile = createNewFile(zipFilePath + File.separator + zipName + ".zip");
        try (FileOutputStream fileOutputStream = new FileOutputStream(zipFile)) {
            compressFile(sourceFile, fileOutputStream);
        }
    }

    /**
     * 獲取壓縮文件流
     *
     * @param sourceFilePath
     * @return ByteArrayOutputStream
     * @throws IOException
     */
    public static OutputStream compressFile(String sourceFilePath, OutputStream outputStream) throws IOException {
        File sourceFile = new File(sourceFilePath);
        if (!sourceFile.exists()) {
            throw new RuntimeException(sourceFilePath + "不存在！");
        }
        return compressFile(sourceFile, outputStream);
    }

    /**
     * 獲取壓縮文件流
     *
     * @param sourceFile
     * @return ByteArrayOutputStream
     * @throws IOException
     */
    private static OutputStream compressFile(File sourceFile, OutputStream outputStream) throws IOException {
        try (CheckedOutputStream checkedOutputStream = new CheckedOutputStream(outputStream, new CRC32());
             ZipOutputStream zipOutputStream = new ZipOutputStream(checkedOutputStream)) {
            doCompressFile(sourceFile, zipOutputStream, StringUtils.EMPTY);
            return outputStream;
        }
    }

    /**
     * 處理目錄下的文件
     *
     * @param sourceFile
     * @param zipOutputStream
     * @param zipFilePath
     * @throws IOException
     */
    private static void doCompressFile(File sourceFile, ZipOutputStream zipOutputStream, String zipFilePath) throws IOException {
        // 如果文件是隱藏的，不進行壓縮
        if (sourceFile.isHidden()) {
            return;
        }
        if (sourceFile.isDirectory()) {//如果是文件夾
            handDirectory(sourceFile, zipOutputStream, zipFilePath);
        } else {//如果是文件就添加到壓縮包中
            try (FileInputStream fileInputStream = new FileInputStream(sourceFile)) {
                //String fileName = zipFilePath + File.separator + sourceFile.getName();
                String fileName = zipFilePath + sourceFile.getName();
                addCompressFile(fileInputStream, fileName, zipOutputStream);
                //String fileName = zipFilePath.replace("\\", "/") + "/" + sourceFile.getName();
                //addCompressFile(fileInputStream, fileName, zipOutputStream);
            }
        }
    }

    /**
     * 處理文件夾
     *
     * @param dir         文件夾
     * @param zipOut      壓縮包輸出流
     * @param zipFilePath 壓縮包中的文件夾路徑
     * @throws IOException
     */
    private static void handDirectory(File dir, ZipOutputStream zipOut, String zipFilePath) throws IOException {
        File[] files = dir.listFiles();
        if (ArrayUtils.isEmpty(files)) {
            ZipEntry zipEntry = new ZipEntry(zipFilePath + dir.getName() + File.separator);
            zipOut.putNextEntry(zipEntry);
            zipOut.closeEntry();
            return;
        }
        for (File file : files) {
            doCompressFile(file, zipOut, zipFilePath + dir.getName() + File.separator);
        }
    }

    /**
     * 獲取壓縮文件流
     *
     * @param documentList 需要壓縮的文件集合
     * @return ByteArrayOutputStream
     */
    public static OutputStream compressFile(List<FileInfo> documentList, OutputStream outputStream) {
        Map<String, List<FileInfo>> documentMap = new HashMap<>();
        documentMap.put("", documentList);
        return compressFile(documentMap, outputStream);
    }

    /**
     * 將文件打包到zip
     *
     * @param documentMap 需要下載的附件集合 map的key對應(yīng)zip里的文件夾名
     * @return ByteArrayOutputStream
     */
    public static OutputStream compressFile(Map<String, List<FileInfo>> documentMap, OutputStream outputStream) {
        CheckedOutputStream checkedOutputStream = new CheckedOutputStream(outputStream, new CRC32());
        ZipOutputStream zipOutputStream = new ZipOutputStream(checkedOutputStream);
        try {
            for (Map.Entry<String, List<FileInfo>> documentListEntry : documentMap.entrySet()) {
                String dirName = documentMap.size() > 1 ? documentListEntry.getKey() : "";
                Map<String, Integer> fileNameToLen = new HashMap<>();//記錄單個合同號文件夾下每個文件名稱出現(xiàn)的次數(shù)（對重復(fù)文件名重命名）
                for (FileInfo document : documentListEntry.getValue()) {
                    try {
                        //防止單個文件夾下文件名重復(fù) 對重復(fù)的文件進行重命名
                        String documentName = document.getFileName();
                        if (fileNameToLen.get(documentName) == null) {
                            fileNameToLen.put(documentName, 1);
                        } else {
                            int fileLen = fileNameToLen.get(documentName) + 1;
                            fileNameToLen.put(documentName, fileLen);
                            documentName = documentName + "(" + fileLen + ")";
                        }
                        String fileName = documentName + "." + document.getSuffix();
                        if (StringUtils.isNotBlank(dirName)) {
                            fileName = dirName + File.separator + fileName;
                        }
                        addCompressFile(document.getFileInputStream(), fileName, zipOutputStream);
                    } catch (Exception e) {
                        logger.info("filesToZip exception :", e);
                    }
                }
            }
        } catch (Exception e) {
            logger.error("filesToZip exception:" + e.getMessage(), e);
        }
        return outputStream;
    }

    /**
     * 將單個文件寫入文件壓縮包
     *
     * @param inputStream     文件輸入流
     * @param fileName        文件在壓縮包中的相對全路徑
     * @param zipOutputStream 壓縮包輸出流
     */
    private static void addCompressFile(InputStream inputStream, String fileName, ZipOutputStream zipOutputStream) {
        try (BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream)) {
            ZipEntry zipEntry = new ZipEntry(fileName);
            zipOutputStream.putNextEntry(zipEntry);
            byte[] bytes = new byte[1024];
            int length;
            while ((length = bufferedInputStream.read(bytes)) >= 0) {
                zipOutputStream.write(bytes, 0, length);
                zipOutputStream.flush();
            }
            zipOutputStream.closeEntry();
            //System.out.println("map size, value is " + RamUsageEstimator.sizeOf(zipOutputStream));
        } catch (Exception e) {
            logger.info("addFileToZip exception:", e);
            throw new RuntimeException(e);
        }
    }

    /**
     * 通過網(wǎng)絡(luò)請求下載zip
     *
     * @param sourceFilePath       需要壓縮的文件路徑
     * @param response            HttpServletResponse
     * @param zipName            壓縮包名稱
     * @throws IOException
     */
    public static void httpDownloadCompressFile(String sourceFilePath, HttpServletResponse response, String zipName) throws IOException {
        File sourceFile = new File(sourceFilePath);
        if (!sourceFile.exists()) {
            throw new RuntimeException(sourceFilePath + "不存在！");
        }
        if(StringUtils.isBlank(zipName)){
            zipName = sourceFile.getName();
        }
        try (ServletOutputStream servletOutputStream = response.getOutputStream()){
            CompressUtil.compressFile(sourceFile, servletOutputStream);
            response.setContentType("application/zip");
            response.setHeader("Content-Disposition", "attachment; filename=\"" + zipName + ".zip\"");
            servletOutputStream.flush();
        }
    }

    public static void httpDownloadCompressFileOld(String sourceFilePath, HttpServletResponse response, String zipName) throws IOException {
        try (ServletOutputStream servletOutputStream = response.getOutputStream()){
            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            byte[] zipBytes = byteArrayOutputStream.toByteArray();
            response.setContentType("application/zip");
            response.setHeader("Content-Disposition", "attachment; filename=\"" + zipName + ".zip\"");
            response.setContentLength(zipBytes.length);
            servletOutputStream.write(zipBytes);
            servletOutputStream.flush();
        }
    }

    /**
     * 通過網(wǎng)絡(luò)請求下載zip
     *
     * @param sourceFilePath       需要壓縮的文件路徑
     * @param response            HttpServletResponse
     * @throws IOException
     */
    public static void httpDownloadCompressFile(String sourceFilePath, HttpServletResponse response) throws IOException {
        httpDownloadCompressFile(sourceFilePath, response, null);
    }


    /**
     * 檢查文件名是否已經(jīng)存在，如果存在，就在文件名后面加上“(1)”，如果文件名“(1)”也存在，則改為“(2)”，以此類推。如果文件名不存在，就直接創(chuàng)建一個新文件。
     *
     * @param filename 文件名
     * @return File
     */
    public static File createNewFile(String filename) {
        File file = new File(filename);
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } else {
            String base = filename.substring(0, filename.lastIndexOf("."));
            String ext = filename.substring(filename.lastIndexOf("."));
            int i = 1;
            while (true) {
                String newFilename = base + "(" + i + ")" + ext;
                file = new File(newFilename);
                if (!file.exists()) {
                    try {
                        file.createNewFile();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    break;
                }
                i++;
            }
        }
        return file;
    }
}

FileInfo類代碼：

/**
 * @author fhey
 * @date 2023-05-11 21:01:26
 * @description: TODO
 */
@Data
public class FileInfo {
    private InputStream fileInputStream;

    private String suffix;

    private String fileName;
    
    private boolean isDirectory;
}

測試壓縮并在本地生成文件：

public static void main(String[] args) throws Exception {
        //在本地創(chuàng)建壓縮文件
        CompressUtil.createLocalCompressFile("D:\\書籍\\電子書\\醫(yī)書", "D:\\test");
    }

壓縮并在本地生成文件驗證結(jié)果：

壓縮文件并通過http請求下載：

/**
 * @author fhey
 */
@RestController
public class TestController {

    @GetMapping(value = "/testFileToZip")
    public void testFileToZip(HttpServletResponse response) throws IOException {
        String zipFileName = "myFiles";
        String sourceFilePath = "D:\\picture";
        CompressUtil.httpDownloadCompressFile(sourceFilePath,response, zipFileName);
    }
}

壓縮文件并通過http請求下載驗證結(jié)果：
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