在Java中确定二进制/文本文件类型？

Question

也就是说,如何从文本(xml/txt,独立于编码)文件中记录存档(jar/rar/etc.)文件？

Answer 1

没有保证的方法,但这里有几种可能性:

1)在文件上查找标题.遗憾的是,标题是特定于文件的,因此虽然您可能会发现它是一个RAR文件,但您无法获得更为通用的答案,无论是文本还是二进制文件.

2)计算字符与非字符类型的数量.文本文件主要是字母字符,而二进制文件 - 尤其是rar,zip等压缩文件 - 往往会更均匀地表示字节.

3)寻找定期重复的换行模式.

Answer 2

跑file -bi {filename}.如果它返回的是以'text /'开头的,则它是非二进制的,否则就是.;-)

Answer 3

我做了这个.有点简单,但对于基于拉丁语言,它应该工作正常,比率调整.

/**
 *  Guess whether given file is binary. Just checks for anything under 0x09.
 */
public static boolean isBinaryFile(File f) throws FileNotFoundException, IOException {
    FileInputStream in = new FileInputStream(f);
    int size = in.available();
    if(size > 1024) size = 1024;
    byte[] data = new byte[size];
    in.read(data);
    in.close();

    int ascii = 0;
    int other = 0;

    for(int i = 0; i < data.length; i++) {
        byte b = data[i];
        if( b < 0x09 ) return true;

        if( b == 0x09 || b == 0x0A || b == 0x0C || b == 0x0D ) ascii++;
        else if( b >= 0x20  &&  b <= 0x7E ) ascii++;
        else other++;
    }

    if( other == 0 ) return false;

    return 100 * other / (ascii + other) > 95;
}

Answer 4

看看JMimeMagic库.

jMimeMagic是一个用于确定文件或流的MIME类型的Java库.

Answer 5

使用Java 7 Files类http://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#probeContentType(java.nio.file.Path)

boolean isBinaryFile(File f) throws IOException {
        String type = Files.probeContentType(f.toPath());
        if (type == null) {
            //type couldn't be determined, assume binary
            return true;
        } else if (type.startsWith("text")) {
            return false;
        } else {
            //type isn't text
            return true;
        }
    }

Answer 6

我使用了这段代码,它适用于英语和德语文本:

private boolean isTextFile(String filePath) throws Exception {
    File f = new File(filePath);
    if(!f.exists())
        return false;
    FileInputStream in = new FileInputStream(f);
    int size = in.available();
    if(size > 1000)
        size = 1000;
    byte[] data = new byte[size];
    in.read(data);
    in.close();
    String s = new String(data, "ISO-8859-1");
    String s2 = s.replaceAll(
            "[a-zA-Z0-9ßöäü\\.\\*!\"§\\$\\%&/()=\\?@~'#:,;\\"+
            "+><\\|\\[\\]\\{\\}\\^°²³\\\\ \\n\\r\\t_\\-`´âêîô"+
            "ÂÊÔÎáéíóàèìòÁÉÍÓÀÈÌÒ©‰¢£¥€±¿»«¼½¾™ª]", "");
    // will delete all text signs

    double d = (double)(s.length() - s2.length()) / (double)(s.length());
    // percentage of text signs in the text
    return d > 0.95;
}