spark java: how to handle multipart/form-data input?

Question

I am using spark to develop a web application; the problem occurs when I want to upload a file:

public final class SparkTesting
{
    public static void main(final String... args)
    {
        Spark.staticFileLocation("/site");

        Spark.port(8080);

        Spark.post("/upload", (request, response) -> {
            final Part uploadedFile = request.raw().getPart("uploadedFile");
            final Path path = Paths.get("/tmp/meh");
            try (final InputStream in = uploadedFile.getInputStream()) {
                Files.copy(in, path);
            }

            response.redirect("/");
            return "OK";
        });
    }
}

But I get this error:

[qtp509057984-36] ERROR spark.webserver.MatcherFilter - 
java.lang.IllegalStateException: No multipart config for servlet
    at org.eclipse.jetty.server.Request.getPart(Request.java:2039)
    at javax.servlet.http.HttpServletRequestWrapper.getPart(HttpServletRequestWrapper.java:361)
    at com.github.fge.grappa.debugger.web.SparkTesting.lambda$main$0(SparkTesting.java:20)
    at com.github.fge.grappa.debugger.web.SparkTesting$$Lambda$1/920011586.handle(Unknown Source)
    at spark.SparkBase$1.handle(SparkBase.java:264)
    at spark.webserver.MatcherFilter.doFilter(MatcherFilter.java:154)
    at spark.webserver.JettyHandler.doHandle(JettyHandler.java:60)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:179)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:136)
    at org.eclipse.jetty.server.handler.HandlerList.handle(HandlerList.java:52)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:451)
    at org.eclipse.jetty.server.HttpChannel.run(HttpChannel.java:252)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:266)
    at org.eclipse.jetty.io.AbstractConnection$ReadCallback.run(AbstractConnection.java:240)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:596)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:527)
    at java.lang.Thread.run(Thread.java:745)

And even if I try and specify the type explicitly, as in:

Spark.post("/upload", "multipart/form-data", etc etc)

it will still fail.

I could probably find a library to parse multipart/form-data, grab the whole content and just parse myself, but that'd be a waste.

Can I configure spark to handle that case?

Answer 1

The answer provided by Kai Yao is correct except that when using:

request.raw().setAttribute("org.eclipse.multipartConfig", multipartConfigElement);

use this instead:

request.raw().setAttribute("org.eclipse.jetty.multipartConfig", multipartConfigElement);

Answer 2

By adding a few lines of code to add the multipart config, you can handle multipart/form-data without an external library:

public Object handle(Request request, Response response) {
    MultipartConfigElement multipartConfigElement = new MultipartConfigElement("/tmp");
    request.raw().setAttribute("org.eclipse.multipartConfig", multipartConfigElement);
    ....
    Part file = request.raw().getPart("file"); //file is name of the upload form
}

Source: http://deniz.dizman.org/file-uploads-using-spark-java-micro-framework/