利用文件头来判断文件类型

利用文件头来实现的一些文件类型的方法封装

package com.opslab.util.algorithmImpl;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
* 利用文件头来实现的一些文件类型的方法封装
*/
public class FileTypeImpl {

public final static Map<String,String> FILE_TYPE_MAP = new HashMap<String,String>();

static {
FILE_TYPE_MAP.put("jpg", "FFD8FF"); //JPEG (jpg)
FILE_TYPE_MAP.put("png", "89504E47"); //PNG (png)
FILE_TYPE_MAP.put("gif", "47494638"); //GIF (gif)
FILE_TYPE_MAP.put("tif", "49492A00"); //TIFF (tif)
FILE_TYPE_MAP.put("bmp", "424D"); //Windows Bitmap (bmp)
FILE_TYPE_MAP.put("dwg", "41433130"); //CAD (dwg)
FILE_TYPE_MAP.put("html", "68746D6C3E"); //HTML (html)
FILE_TYPE_MAP.put("rtf", "7B5C727466"); //Rich Text Format (rtf)
FILE_TYPE_MAP.put("xml", "3C3F786D6C");
FILE_TYPE_MAP.put("zip", "504B0304");
FILE_TYPE_MAP.put("rar", "52617221");
FILE_TYPE_MAP.put("psd", "38425053"); //Photoshop (psd)
FILE_TYPE_MAP.put("eml", "44656C69766572792D646174653A"); //Email [thorough only] (eml)
FILE_TYPE_MAP.put("dbx", "CFAD12FEC5FD746F"); //Outlook Express (dbx)
FILE_TYPE_MAP.put("pst", "2142444E"); //Outlook (pst)
FILE_TYPE_MAP.put("xls", "D0CF11E0"); //MS Word
FILE_TYPE_MAP.put("doc", "D0CF11E0"); //MS Excel 注意：word 和 excel的文件头一样
FILE_TYPE_MAP.put("mdb", "5374616E64617264204A"); //MS Access (mdb)
FILE_TYPE_MAP.put("wpd", "FF575043"); //WordPerfect (wpd)
FILE_TYPE_MAP.put("eps", "252150532D41646F6265");
FILE_TYPE_MAP.put("ps", "252150532D41646F6265");
FILE_TYPE_MAP.put("pdf", "255044462D312E"); //Adobe Acrobat (pdf)
FILE_TYPE_MAP.put("qdf", "AC9EBD8F"); //Quicken (qdf)
FILE_TYPE_MAP.put("pwl", "E3828596"); //Windows Password (pwl)
FILE_TYPE_MAP.put("wav", "57415645"); //Wave (wav)
FILE_TYPE_MAP.put("avi", "41564920");
FILE_TYPE_MAP.put("ram", "2E7261FD"); //Real Audio (ram)
FILE_TYPE_MAP.put("rm", "2E524D46"); //Real Media (rm)
FILE_TYPE_MAP.put("mpg", "000001BA"); //
FILE_TYPE_MAP.put("mov", "6D6F6F76"); //Quicktime (mov)
FILE_TYPE_MAP.put("asf", "3026B2758E66CF11"); //Windows Media (asf)
FILE_TYPE_MAP.put("mid", "4D546864"); //MIDI (mid)
}

/**
* Created on 2010-7-1
* <p>Discription:[getFileByFile,获取文件类型,包括图片,若格式不是已配置的,则返回null]</p>
*
* @param file
* @return fileType
* @author:[shixing_11@sina.com]
*/
public final static String getFileType(File file) {
String filetype = null;
byte[] b = new byte[50];
try (
InputStream is = new FileInputStream(file)
) {
is.read(b);
filetype = getFileTypeByStream(b);
is.close();
} catch (IOException e) {
e.printStackTrace();
}
return filetype;
}

/**
* Created on 2010-7-1
* <p>Discription:[getFileTypeByStream]</p>
*
* @param b
* @return fileType
* @author:[shixing_11@sina.com]
*/
public final static String getFileTypeByStream(byte[] b) {
String filetypeHex = String.valueOf(getFileHexString(b));
Iterator<Map.Entry<String,String>> entryiterator = FILE_TYPE_MAP.entrySet().iterator();
while (entryiterator.hasNext()) {
Map.Entry<String,String> entry = entryiterator.next();
String fileTypeHexValue = entry.getValue();
if (filetypeHex.toUpperCase().startsWith(fileTypeHexValue)) {
return entry.getKey();
}
}
return null;
}

/**
* Created on 2010-7-1
* <p>Discription:[getFileHexString]</p>
*
* @param b
* @return fileTypeHex
* @author:[shixing_11@sina.com]
*/
public final static String getFileHexString(byte[] b) {
StringBuilder stringBuilder = new StringBuilder();
if (b == null || b.length <= 0) {
return null;
}
for (int i = 0; i < b.length; i++) {
int v = b[i] & 0xFF;
String hv = Integer.toHexString(v);
if (hv.length() < 2) {
stringBuilder.append(0);
}
stringBuilder.append(hv);
}
return stringBuilder.toString();
}
}