How to convert a byte [] from an image to a jpeg image to load in html?

In the html (jsp) of register I have a field that the user registers his photo getting the tag img with the following result.

<img src="data:image/png;Base64,/9/0kmkdmkewnsjdncijndcjdxncdjcdscjnccc/ccnkjdncnsjnidckcmokcmoskcmkosmcokmdscjncjncjcsnckdjncojnscjncdjnckmkdmcokscmksmdckcmsokcmnjncjemncmokkjcmdjsdccmslckjplqmkmokswkmxokamlamklmockmclmdkcmlodkcmokcmkmcokmsomcksmcsfhhgfrfcghjkuytredfhjolkjhsSWswjshuhuwhuhyhuimcoskcmkmsckmkmkcmc"
/>

I am converting the excerpt Base64, to a byte [] with sun.misc.BASE64Decoder, as below:

import Decoder.BASE64Decoder;
import Decoder.BASE64Encoder;

/**
* @author Tiago Ferezin
* 
* para o tratamento da imagem
*
*/
public class Imagem {

public static byte[] convertBase64StringToByteArray(String imagem){
    byte[] retorno = null;

    try {
        BASE64Decoder decoder = new BASE64Decoder();
        retorno = decoder.decodeBuffer(imagem);
    } catch (Exception e) {
        // TODO: handle exception
        e.printStackTrace();
    }

    return retorno;

}

public static String convertByteArrayToBase64String(byte[] imagem){
    String retorno="";

    try {
        BASE64Encoder encoder = new BASE64Encoder();
        retorno = encoder.encode(imagem);
    } catch (Exception e) {
        // TODO: handle exception
        e.printStackTrace();
    }

    return retorno;
}

}

And save the generated byte to the bank.

First I wanted to know how before writing to the bank, get the image type (png, ttf, jpg, psd) and convert it to JPEG , and then generate an array of it and write to the bank?

Second, I would like to know how to convert this byte [] stored in the database to a String data:image/jpeg;Base64,{byte[]} to put in a img tag on another JSP page?