CompressUtil Java Utility for File Compression and Download

Sometimes a system needs to download multiple files at once, and downloading them one by one is cumbersome. The best solution is to package all files into a compressed archive and download that archive, allowing all required files to be obtained in a single operation.

The following code defines a utility class called CompressUtil that offers several methods for handling file compression and download operations.

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: Compression utility class
 */
public class CompressUtil {
    private static final Logger logger = LoggerFactory.getLogger(CompressUtil.class);

    /**
     * Pack files into a zip and create the file
     * @param sourceFilePath
     * @param zipFilePath
     * @throws IOException
     */
    public static void createLocalCompressFile(String sourceFilePath, String zipFilePath) throws IOException {
        createLocalCompressFile(sourceFilePath, zipFilePath, null);
    }

    /**
     * Pack files into a zip and create the file
     * @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);
        }
    }

    /**
     * Get compression file stream
     * @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);
    }

    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;
        }
    }

    private static void doCompressFile(File sourceFile, ZipOutputStream zipOutputStream, String zipFilePath) throws IOException {
        // Skip hidden files
        if (sourceFile.isHidden()) {
            return;
        }
        if (sourceFile.isDirectory()) {
            handDirectory(sourceFile, zipOutputStream, zipFilePath);
        } else {
            try (FileInputStream fileInputStream = new FileInputStream(sourceFile)) {
                String fileName = zipFilePath + sourceFile.getName();
                addCompressFile(fileInputStream, fileName, zipOutputStream);
            }
        }
    }

    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);
        }
    }

    public static OutputStream compressFile(List
documentList, OutputStream outputStream) {
        Map
> documentMap = new HashMap<>();
        documentMap.put("", documentList);
        return compressFile(documentMap, outputStream);
    }

    public static OutputStream compressFile(Map
> documentMap, OutputStream outputStream) {
        CheckedOutputStream checkedOutputStream = new CheckedOutputStream(outputStream, new CRC32());
        ZipOutputStream zipOutputStream = new ZipOutputStream(checkedOutputStream);
        try {
            for (Map.Entry
> documentListEntry : documentMap.entrySet()) {
                String dirName = documentMap.size() > 1 ? documentListEntry.getKey() : "";
                Map
fileNameToLen = new HashMap<>();
                for (FileInfo document : documentListEntry.getValue()) {
                    try {
                        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;
    }

    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();
        } catch (Exception e) {
            logger.info("addFileToZip exception:", e);
            throw new RuntimeException(e);
        }
    }

    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();
        }
    }

    public static void httpDownloadCompressFile(String sourceFilePath, HttpServletResponse response) throws IOException {
        httpDownloadCompressFile(sourceFilePath, response, null);
    }

    /**
     * Check if a file name already exists; if it does, append "(1)", "(2)", etc.
     * @param filename File name
     * @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;
    }
}

Test compression and generate a local file:

public static void main(String[] args) throws Exception {
    // Create a zip file locally
    CompressUtil.createLocalCompressFile("D:\\书籍\\电子书\\医书", "D:\\test");
}

The result of compressing and generating the file locally can be verified (image omitted).

Compress the file and download it via an HTTP request:

@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);
    }
}

The result of downloading the compressed file through HTTP can be verified (image omitted).