验证文件是否已在 Java 中复制

发布于 2024-10-10 17:58:31 字数 380 浏览 15 评论 0原文

我正在努力将一些文件移动到项目中的不同目录，并且效果很好，除了我无法验证它是否已正确移动这一事实。

我想验证副本的长度与原始文件的长度相同，然后我想删除原始文件。我在进行验证之前关闭了两个 FileStream，但由于大小不同，它仍然失败。下面是我用于关闭流、验证和删除的代码。

 in.close();
 out.close();

 if (encCopyFile.exists() && encCopyFile.length() == encryptedFile.length())
     encryptedFile.delete();

在此之前的其余代码是使用 Util 来复制流，并且一切正常，所以我实际上只需要一个更好的验证方法。

原文

I'm working on moving some files to a different directory in my project and it's working great, except for the fact that I can't verify it's moved properly.

I want to verify the length of the copy is the same as the original and then I want to delete the original. I'm closing both FileStreams before I do my verification but it still fails because the sizes are different. Below is my code for closing the streams, verification and deletion.

 in.close();
 out.close();

 if (encCopyFile.exists() && encCopyFile.length() == encryptedFile.length())
     encryptedFile.delete();

The rest of the code before this is using a Util to copy the streams, and it's all working fine so really I just need a better verification method.

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晨与橙与城 2024-10-17 17:58:32

一种很好的检查方法是比较 md5 哈希值。检查文件长度并不意味着它们是相同的。虽然 md5 哈希值也不意味着它们相同，但它比检查长度要好，尽管过程较长。

public class Main {

    public static void main(String[] args) throws NoSuchAlgorithmException, IOException {
        System.out.println("Are identical: " + isIdentical("c:\\myfile.txt", "c:\\myfile2.txt"));
    }

    public static boolean isIdentical(String leftFile, String rightFile) throws IOException, NoSuchAlgorithmException {
        return md5(leftFile).equals(md5(rightFile));
    }

    private static String md5(String file) throws IOException, NoSuchAlgorithmException {
        MessageDigest digest = MessageDigest.getInstance("MD5");
        File f = new File(file);
        InputStream is = new FileInputStream(f);
        byte[] buffer = new byte[8192];
        int read = 0;
        try {
            while ((read = is.read(buffer)) > 0) {
                digest.update(buffer, 0, read);
            }
            byte[] md5sum = digest.digest();
            BigInteger bigInt = new BigInteger(1, md5sum);
            String output = bigInt.toString(16);
            return output;
        } finally {
            is.close();
        }
    }
}

One wonderful way you can check is to compare md5 hashes. Checking file length doesn't mean they are the same. While md5 hashes doesn't mean they are the same either, it is better than checking the length albeit a longer process.

public class Main {

    public static void main(String[] args) throws NoSuchAlgorithmException, IOException {
        System.out.println("Are identical: " + isIdentical("c:\\myfile.txt", "c:\\myfile2.txt"));
    }

    public static boolean isIdentical(String leftFile, String rightFile) throws IOException, NoSuchAlgorithmException {
        return md5(leftFile).equals(md5(rightFile));
    }

    private static String md5(String file) throws IOException, NoSuchAlgorithmException {
        MessageDigest digest = MessageDigest.getInstance("MD5");
        File f = new File(file);
        InputStream is = new FileInputStream(f);
        byte[] buffer = new byte[8192];
        int read = 0;
        try {
            while ((read = is.read(buffer)) > 0) {
                digest.update(buffer, 0, read);
            }
            byte[] md5sum = digest.digest();
            BigInteger bigInt = new BigInteger(1, md5sum);
            String output = bigInt.toString(16);
            return output;
        } finally {
            is.close();
        }
    }
}

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苏大泽ㄣ 2024-10-17 17:58:32

您可以在复制操作中包含校验和。对目标文件执行校验和，并查看它是否与源文件上的校验和匹配。

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筱果果 2024-10-17 17:58:32

您可以使用 commons io:

org.apache.commons.io.FileUtils.contentEquals(File file1, File file2)

或者可以使用校验和方法：

org.apache.commons.io.FileUtils:
static Checksum checksum(File file, Checksum checksum) //Computes the checksum of a file using the specified checksum object.
static long checksumCRC32(File file) //Computes the checksum of a file using the CRC32 checksum routine.

You could use commons io:

org.apache.commons.io.FileUtils.contentEquals(File file1, File file2)

or you could use checksum methods:

org.apache.commons.io.FileUtils:
static Checksum checksum(File file, Checksum checksum) //Computes the checksum of a file using the specified checksum object.
static long checksumCRC32(File file) //Computes the checksum of a file using the CRC32 checksum routine.

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