web判断文件的格式的时候,我们一般都是通过扩展名来判断,这个有点不太靠谱和安全。一般要判断是利用头文件来判断。下面是利用头文件来判断的代码:
package com.app.util; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; public class T { public static String bytesToHexString(byte[] src){ StringBuilder strBuilder = new StringBuilder(); if (src == null || src.length <= 0) { return null; } for (int i = 0; i < src.length; i++) { int v = src[i] & 0xFF; String strhs = Integer.toHexString(v); if (strhs.length() < 2) { strBuilder.append(0); } strBuilder.append(strhs); } return strBuilder.toString(); } /** * 根据文件流读取图片文件真实类型 * @param is * @return */ public static String getTypeByStream(FileInputStream is) { byte[] b = new byte[4]; try { is.read(b, 0, b.length); } catch (IOException e) { e.printStackTrace(); } String type = bytesToHexString(b).toUpperCase(); if (type.contains("FFD8FF")) { return "jpg"; } else if (type.contains("89504E47")) { return "png"; } else if (type.contains("47494638")) { return "gif"; } else if (type.contains("49492A00")) { return "tif"; } else if (type.contains("424D")) { return "bmp"; } return type; } public static void main(String args[]) { // String src = "D:/workspace//8129.jpg"; // String src = "D:/workspace//temp/1.gif"; String src = "D:/003-004-join.jpg"; FileInputStream is = null; try { is = new FileInputStream(src); } catch (FileNotFoundException e) { e.printStackTrace(); } // byte[] b = new byte[4]; // is.read(b, 0, b.length); // System.out.println(bytesToHexString(b)); String type = getTypeByStream(is); System.out.println(type); } }
网上搜索了一些头文件的格式,但是强调一下,txt文件没有固定的头名,需要另外考虑,供参考:
- 用文件头判断。直接读取文件的前几个字节。
- 常用文件的文件头如下:
- JPEG (jpg),文件头:FFD8FF
- PNG (png),文件头:89504E47
- GIF (gif),文件头:47494638
- TIFF (tif),文件头:49492A00
- Windows Bitmap (bmp),文件头:424D
- CAD (dwg),文件头:41433130
- Adobe Photoshop (psd),文件头:38425053
- Rich Text Format (rtf),文件头:7B5C727466
- XML (xml),文件头:3C3F786D6C
- HTML (html),文件头:68746D6C3E
- Email [thorough only] (eml),文件头:44656C69766572792D646174653A
- Outlook Express (dbx),文件头:CFAD12FEC5FD746F
- Outlook (pst),文件头:2142444E
- MS Word/Excel (xls.or.doc),文件头:D0CF11E0
- MS Access (mdb),文件头:5374616E64617264204A
- WordPerfect (wpd),文件头:FF575043
- Postscript. (eps.or.ps),文件头:252150532D41646F6265
- Adobe Acrobat (pdf),文件头:255044462D312E
- Quicken (qdf),文件头:AC9EBD8F
- Windows Password (pwl),文件头:E3828596
- ZIP Archive (zip),文件头:504B0304
- RAR Archive (rar),文件头:52617221
- Wave (wav),文件头:57415645
- AVI (avi),文件头:41564920
- Real Audio (ram),文件头:2E7261FD
- Real Media (rm),文件头:2E524D46
- MPEG (mpg),文件头:000001BA
- MPEG (mpg),文件头:000001B3
- Quicktime (mov),文件头:6D6F6F76
- Windows Media (asf),文件头:3026B2758E66CF11
- MIDI (mid),文件头:4D546864