java通过文件头来判断文件类型
package cn.com.songjy.test.io;import java.awt.image.BufferedImage;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;import java.util.HashMap;import java.util.Iterator;import java.util.Map;import java.util.Map.Entry;import javax.imageio.ImageIO;import javax.imageio.ImageReader;import javax.imageio.stream.ImageInputStream;public class FileTypeUtils {public final static Map<String, String> FILE_TYPE_MAP = new HashMap<String, String>();private FileTypeUtils() {}static {getAllFileType(); // 初始化文件类型信息}/** * Created on 2013-1-21 * <p> * Discription:[getAllFileType,常见文件头信息] * * @author:shaochangfu */private static void getAllFileType() {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("bmp", "424D"); // Windows Bitmap (bmp)FILE_TYPE_MAP.put("zip", "504B0304");// zip 压缩文件}public static void main(String[] args) throws Exception {File f = new File("/home/newpro/桌面/2013-1-17-2.png");File f2 = new File("/home/newpro/桌面/Screenshot.Png");File f3 = new File("/home/newpro/桌面/Screenshot.zip");File f4 = new File("/home/newpro/桌面/svn插件1.6.zip");// 判断是否是iamge,是image 并且后缀名 是 JPEG,PNG,GIF BMPSystem.out.println(isImage(f) + "is image");System.out.println(isImage(f2) + "is image");System.out.println(getImageFileType(f) + " is image");System.out.println(getImageFileType(f2) + " is image");// 判断是否是zipSystem.out.println(getFileByFile(f3) + " is zip");System.out.println(getFileByFile(f4) + " is zip");}/** * Created on 2013-1-21 * <p> * Discription:[getImageFileType,获取图片文件实际类型,若不是图片则返回null] * </p> * * @param File * @return fileType * @author:shaochangfu */public final static String getImageFileType(File f) {if (isImage(f)) {try {ImageInputStream iis = ImageIO.createImageInputStream(f);Iterator<ImageReader> iter = ImageIO.getImageReaders(iis);if (!iter.hasNext()) {return null;}ImageReader reader = iter.next();iis.close();return reader.getFormatName();} catch (IOException e) {e.printStackTrace();return null;} catch (Exception e) {e.printStackTrace();return null;}}return null;}/** * Created on 2013-1-21 * <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:shaochangfu */public final static String getFileByFile(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 (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}return filetype;}/** * Created on 2013-1-21 * <p> * Discription:[getFileTypeByStream] * </p> * * @param b * @return fileType * @author:shaochangfu */public final static String getFileTypeByStream(byte[] b) {String filetypeHex = String.valueOf(getFileHexString(b));Iterator<Entry<String, String>> entryiterator = FILE_TYPE_MAP.entrySet().iterator();while (entryiterator.hasNext()) {Entry<String, String> entry = entryiterator.next();String fileTypeHexValue = entry.getValue();if (filetypeHex.toUpperCase().startsWith(fileTypeHexValue)) {return entry.getKey();}}return null;}/** * Created on 2013-1-21 * <p> * Discription:[isImage,判断文件是否为图片] * </p> * * @param file * @return true 是 | false 否 * @author:shaochangfu */public static final boolean isImage(File file) {boolean flag = false;try {BufferedImage bufreader = ImageIO.read(file);int width = bufreader.getWidth();int height = bufreader.getHeight();if (width == 0 || height == 0) {flag = false;} else {flag = true;}} catch (IOException e) {flag = false;} catch (Exception e) {flag = false;}return flag;}/** * Created on 2013-1-21 * <p> * Discription:[getFileHexString] * </p> * * @param b * @return fileTypeHex * @author:shaochangfu */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();}}