Create and serve a Zip archive from within DropWizard

Zip by Stefano Mortellaro

Zip by Stefano Mortellaro

Do you want your DropWizard app to create and serve a zip archive to users? If you’ve got a lot of data then you should periodically create an archive and store it on a CDN for people to download. But if you’ve got a small amount of data, then here’s some code to do it.

@GET
@Path("/download")
@Produces(MediaType.APPLICATION_OCTET_STREAM)
public Response download() {
    StreamingOutput stream = new StreamingOutput() {
        @Override
        public void write(OutputStream output) throws IOException, WebApplicationException {
            ZipOutputStream zos = new ZipOutputStream(output);
 
            ZipEntry ze = new ZipEntry("file.txt");
            zos.putNextEntry(ze);
            zos.write("file.txt".getBytes());
            zos.closeEntry();
 
            ze = new ZipEntry("item/item1.txt");
            zos.putNextEntry(ze);
            zos.write("item/item1.txt".getBytes());
            zos.closeEntry();
 
            zos.flush();
            zos.close();
        }
    };
 
    return Response
            .ok(stream)
            .header("Content-Disposition", "attachment; filename=download.zip")
            .header("Content-Transfer-Encoding", "binary")
            .build();
}

ZipEntry ze = new ZipEntry("file.txt");
zos.putNextEntry(ze);
zos.write("file.txt".getBytes());
zos.closeEntry();

ze = new ZipEntry("item/item1.txt");
zos.putNextEntry(ze);
zos.write("item/item1.txt".getBytes());
zos.closeEntry();

zos.flush();
zos.close();
}
};

return Response
.ok(stream)
.header("Content-Disposition", "attachment; filename=download.zip")
.header("Content-Transfer-Encoding", "binary")
.build();
}

You’ll need to ensure you don’t write the same filename to the zip more than once to avoid a ZipException.

And if you’re using an ObjectMapper to write JSON objects into the archive stream, you’ll need to stop it closing the stream after writing:-

ObjectMapper om = new ObjectMapper();
om.configure(JsonGenerator.Feature.AUTO_CLOSE_TARGET, false);

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