画像と文字列の相互変換

try{
		OutputStream o = response.getOutputStream();
		
		//  
		File f = new File("f:\\Vista.png");
		FileInputStream fis = new FileInputStream( f );
		byte[] bytes = new byte[fis.available()];
		fis.read(bytes);
		fis.close();
		
		//  
		String imgStr = byte2hex( bytes );
		System.out.println( imgStr);
		
		//  ， 
		//   imgStr， 
		byte[] imgByte = hex2byte( imgStr );
		InputStream in = new ByteArrayInputStream( imgByte );
		
		byte[] b = new byte[1024];
		int nRead = 0;
		while( ( nRead = in.read(b) ) != -1 ){
			o.write( b, 0, nRead );
		}
		o.flush();
		o.close();
		in.close();
		
		
	}catch(Exception e){
		e.printStackTrace();
	}finally{
	}

public static String byte2hex(byte[] b) //  
{
   StringBuffer sb = new StringBuffer();
   String stmp = "";
   for (int n = 0; n < b.length; n++) {
    stmp = Integer.toHexString(b[n] & 0XFF);
    if (stmp.length() == 1){
    	sb.append("0" + stmp);
    }else{
    	sb.append(stmp);
    }
    
   }
   return sb.toString();
}

public static byte[] hex2byte(String str) { //  
    if (str == null)
     return null;
    str = str.trim();
    int len = str.length();
    if (len == 0 || len % 2 == 1)
     return null;
    byte[] b = new byte[len / 2];
    try {
     for (int i = 0; i < str.length(); i += 2) {
      b[i / 2] = (byte) Integer.decode("0X" + str.substring(i, i + 2)).intValue();
     }
     return b;
    } catch (Exception e) {
     return null;
    }
 }