Download svg as png (or svg) with Java backend support - http://notes.webutvikling.org/converting-svg-to-png-with-javascript/

index.html

<form method="POST" action="http://localhost:2222/rest/download/png" onSubmit="getSvg(this)">
	<input type="hidden" value="" name="data" type="text" />
	<button type="submit">GO</button>
</form>

<div class="svg-wrapper">
	<svg height="140" width="500">
  		<ellipse cx="200" cy="80" rx="100" ry="50" style="fill:yellow;stroke:purple;stroke-width:2" />
  	</svg>
</div>

<script>
	
	var getSvg = function(element) {
		var svgHtml = document.querySelector('.svg-wrapper').innerHTML;
		element.querySelector('input').value = svgHtml;
	}
</script>

service.java

package mypackage;

import javax.ws.rs.*;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

import org.apache.batik.transcoder.TranscoderException;
import org.apache.batik.transcoder.image.PNGTranscoder;
import org.apache.batik.transcoder.TranscoderInput;
import org.apache.batik.transcoder.TranscoderOutput;

import java.io.*;

@Path("download")
public class ImageService {

    @POST
    @Path("svg")
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    @Produces(MediaType.APPLICATION_OCTET_STREAM)
    public Response getSvg(
            @FormParam("data") String data,
            @FormParam("fileName") String fileName) {
        if (fileName == null || fileName.isEmpty()) {
            fileName = "img";
        }

        String svgFile = data.replace("<svg", "<svg xmlns=\"http://www.w3.org/2000/svg\"");
        return Response.ok(svgFile, MediaType.APPLICATION_OCTET_STREAM)
                .header("Content-Disposition", "attachment; filename=\"" + fileName + ".svg\"")
                .build();
    }

    @POST
    @Path("png")
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    @Produces(MediaType.APPLICATION_OCTET_STREAM)
    public Response getPng(
            @FormParam("data") String data,
            @FormParam("fileName") String fileName) {
        if (fileName == null || fileName.isEmpty()) {
            fileName = "img";
        }

        String svgFile = data.replace("<svg", "<svg xmlns=\"http://www.w3.org/2000/svg\"");

        InputStream svgFileStream;
        try {
            svgFileStream = new ByteArrayInputStream(svgFile.getBytes("UTF-8"));
        } catch (UnsupportedEncodingException e) {
            svgFileStream = new ByteArrayInputStream(svgFile.getBytes());
            System.out.println("Could not get StringBytes in UTF-8");
            e.printStackTrace();
        }
        TranscoderInput inputSvgImage = new TranscoderInput(svgFileStream);
        PNGTranscoder converter = new PNGTranscoder();
        ByteArrayOutputStream pngFileStream = new java.io.ByteArrayOutputStream();
        TranscoderOutput outputPngImage = new TranscoderOutput(pngFileStream);

        try {
            converter.transcode(inputSvgImage, outputPngImage);
        } catch (TranscoderException e) {
            System.out.println("Error while converting svg to PNG");
            e.printStackTrace();
        }
        return Response.ok(pngFileStream.toByteArray(), MediaType.APPLICATION_OCTET_STREAM)
                .header("Content-Disposition", "attachment; filename=\"" + fileName + ".png\"")
                .build();
    }


}