Question

我使用zip存档实现了从应用程序备份用户数据，我将数据库和共享首选项文件复制到zip存档并计算输入文件的MD5校验和，以防止用户修改备份数据。

要从存档还原，我将备份文件解压缩到临时目录，检查校验和，然后复制相应文件夹中的preferences \ database文件。

我的一些用户抱怨该应用会生成损坏的备份文件（zip文件确实已损坏）。

以下是将所有文件压缩为zip文件的代码：

public void backup(String filename) {
    File file = new File(getBackupDirectory(), filename);
    FileOutputStream fileOutputStream = null;
    ZipOutputStream stream = null;
    try {
        String settingsMD5 = null;
        String databaseMD5 = null;
        if (file.exists())
            file.delete();
        fileOutputStream = new FileOutputStream(file);
        stream = new ZipOutputStream(new BufferedOutputStream(fileOutputStream));
        File database = getDatabasePath(databaseFileName);
        File dataDirectory = getFilesDir();
        if (dataDirectory != null) {
            File settings = new File(dataDirectory.getParentFile(), "/shared_prefs/" + PREFERENCES_FILENAME);
            settingsMD5 = zipFile("preferences", stream, settings);
        }
        databaseMD5 = zipFile("database.db", stream, database);

        JSONObject jsonObject = new JSONObject();
        try {
            jsonObject.put(META_DATE, new SimpleDateFormat(DATE_FORMAT, Locale.US).format(new Date()));
            jsonObject.put(META_DATABASE, databaseMD5);
            jsonObject.put(META_SHARED_PREFS, settingsMD5);
        } catch (Exception e) {
            e.printStackTrace();
        }

        InputStream metadata = new ByteArrayInputStream(jsonObject.toString().getBytes("UTF-8"));
        zipInputStream(stream, metadata, new ZipEntry("metadata"));
        stream.finish();
        stream.close();
        stream = null;
        return file;
    } catch (FileNotFoundException e) {
     //handling errrors
    } catch (IOException e) {
     //handling errrors
    } 
}

private String zipFile(String name, ZipOutputStream zipStream, File file) throws FileNotFoundException, IOException {
        ZipEntry zipEntry = new ZipEntry(name);
        return zipInputStream(zipStream, new FileInputStream(file), zipEntry);
    }

private String zipInputStream(ZipOutputStream zipStream, InputStream fileInputStream, ZipEntry zipEntry) throws IOException {
    InputStream inputStream = new BufferedInputStream(fileInputStream);
    MessageDigest messageDigest = null;
    try {
        messageDigest = MessageDigest.getInstance("MD5");
        if (messageDigest != null)
            inputStream = new DigestInputStream(inputStream, messageDigest);
    } catch (NoSuchAlgorithmException e) {
    }

    zipStream.putNextEntry(zipEntry);
    inputToOutput(inputStream, zipStream);
    zipStream.closeEntry();
    inputStream.close();

    if (messageDigest != null) {
        return getDigestString(messageDigest.digest());
    }
    return null;
}

private String getDigestString(byte[] digest) {
    StringBuffer hexString = new StringBuffer();
    for (int i = 0; i < digest.length; i++) {
        String hex = Integer.toHexString(0xFF & digest[i]);
        if (hex.length() == 1) {
            hex = new StringBuilder("0").append(hex).toString();
        }
        hexString.append(hex);
    }
    return hexString.toString();
}

private void inputToOutput(InputStream inputStream, OutputStream outputStream) throws IOException {
    byte[] buffer = new byte[BUFFER];
    int count = 0;
    while ((count = inputStream.read(buffer, 0, BUFFER)) != -1) {
        outputStream.write(buffer, 0, count);
    }
}

Answer 1

您可以考虑使用zip4j lib。我通过使用这个库解决了我遇到的问题（同样的问题 - 不同的方向）。一些zip文件无法用本机android实现解码，但有zip4j。您也可以使用zip4j进行压缩来解决您的问题。

Answer 2

以下是使用java标准类将目录压缩到文件中的一些代码。有了这个，你可以打电话：

ZipUtils.zip(sourceDirectory, targetFile);
ZipUtils.unzip(sourceFile, targetDirectory);

代码：

package com.my.project.utils.zip;

import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

public class ZipUtils {

    public static void unzip(Path sourceFile, Path targetPath) throws IOException {
        try (ZipInputStream zipInStream = new ZipInputStream(Files.newInputStream(sourceFile))){
            byte[] buffer = new byte[1024];
            Files.createDirectories(targetPath);

            ZipEntry entry = null;

            while ((entry = zipInStream.getNextEntry()) != null){
                Path entryPath = targetPath.resolve(entry.getName());
                Files.createDirectories(entryPath.getParent());
                Files.copy(zipInStream, entryPath);
                zipInStream.closeEntry();
            }
        }
    } 

    public static void zip(Path sourcePath, Path targetFile) throws IOException {
        try (ZipOutputStream zipOutStream = new ZipOutputStream(Files.newOutputStream(targetFile))){
            if (Files.isDirectory(sourcePath)){
                zipDirectory(zipOutStream, sourcePath);
            } else {
                createZipEntry(zipOutStream, sourcePath, sourcePath);
            }
        }
    }

    private static void zipDirectory(ZipOutputStream zip, Path source) throws IOException {
        Files.walkFileTree(source, new SimpleFileVisitor<Path>(){
            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
                return FileVisitResult.CONTINUE;
            }           
            @Override
            public FileVisitResult visitFile(Path path, BasicFileAttributes attrs) throws IOException {
                createZipEntry(zip, source, path);
                return FileVisitResult.CONTINUE;
            }
        });
    }    

    private static void createZipEntry(ZipOutputStream zip, Path sourcePath, Path path) throws IOException {
        ZipEntry entry = new ZipEntry(sourcePath.relativize(path).toString());
        zip.putNextEntry(entry);
        Files.copy(path,zip);
        zip.closeEntry();
    }
}

ZipOutputStream在Android上生成损坏的zip文件

2 个答案: