JAVA图片解析

	public static String getImageType() throws IOException {
            FileInputStream fis = new FileInputStream("PATH");
		
		int leng = fis.available();
		BufferedInputStream buff = new BufferedInputStream(fis);
		byte[] mapObj = new byte[leng];
		buff.read(mapObj, 0, leng);

		String type = "";
		ByteArrayInputStream bais = null;
		MemoryCacheImageInputStream mcis = null;
		try {
			bais = new ByteArrayInputStream(mapObj);
			mcis = new MemoryCacheImageInputStream(bais);
			Iterator itr = ImageIO.getImageReaders(mcis);
			while (itr.hasNext()) {
			ImageReader reader = (ImageReader)  tr.next();
				if (reader instanceof GIFImageReader) {
					type = "gif";
				} else if (reader instanceof JPEGImageReader) {
					type = "jpeg";
				} else if (reader instanceof PNGImageReader) {
					type = "png";
				} else if (reader instanceof BMPImageReader) {
					type = "bmp";
				}
			}
		} finally {
			if (bais != null) {
				try {
					bais.close();
				} catch (IOException ioe) {

				}
			}

			if (mcis != null) {
				try {
					mcis.close();
				} catch (IOException ioe) {

				}
			}
		}
		return type;
	}