Servlet for decode base64 of images. You would change content type for others type.

Base64Servlet.java

package cl.puas.web.servlet;

import sun.misc.BASE64Decoder;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Base64Servlet extends HttpServlet {

    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        String imageBase64 = req.getParameter("base64");
        OutputStream out = resp.getOutputStream();
        writeOutputStream(imageBase64, out);

        resp.setContentType("image/png");
        resp.setHeader("Pragma", "");
        resp.setHeader("Cache-Control", "");
        resp.setHeader("Content-Disposition", "inline; fileName=image.png");
    }

    private void writeOutputStream(String value, OutputStream outputStream) throws IOException {
        BASE64Decoder decoder = new BASE64Decoder();
        byte[] imgBytes = decoder.decodeBuffer(value);
        BufferedImage bufImg = ImageIO.read(new ByteArrayInputStream(imgBytes));
        ImageIO.write(bufImg, "png", outputStream);
    }
}