Spring Integration Aggregator

I want to use an aggregator to create a message out of two messages, but i'm not sure how to do this.

At the moment i'm reading in two files from a directory and want to aggregate those messages into one.

My whole project looks like this:

read in .zip -> pass to custom message handler that unzips it into a directory -> read files from this directory -> try to aggregate them

It would be great if i could send a message with two payloads after unzipping the file, but aggregating after reading it would suffice.

My unzipper looks like this:

public class ZipHandler extends AbstractMessageHandler {

File dat;
File json;

@Override
protected void handleMessageInternal(Message<?> message) throws Exception {
    byte[] buffer = new byte[1024];
    try {
        File file = (File) message.getPayload();
        ZipFile zip = new ZipFile(file);

        for (Enumeration<? extends ZipEntry> entries = zip.entries(); entries
                .hasMoreElements();) {
            ZipEntry ze = entries.nextElement();
            String name = ze.getName();

            if (name.endsWith(".dat") || name.endsWith(".DAT")) {
                InputStream input = zip.getInputStream(ze);
                File datFile = new File("D:/lrtrans/zipOut"
                        + File.separator + name);
                FileOutputStream fos = new FileOutputStream(datFile);
                int len;
                while ((len = input.read(buffer)) > 0) {
                    fos.write(buffer, 0, len);
                }
                this.dat = datFile;
                fos.close();
            } else if (name.endsWith(".json") || name.endsWith(".JSON")) {
                InputStream input = zip.getInputStream(ze);
                File jsonFile = new File("D:/lrtrans/zipOut"
                        + File.separator + name);
                FileOutputStream fos = new FileOutputStream(jsonFile);
                int len;
                while ((len = input.read(buffer)) > 0) {
                    fos.write(buffer, 0, len);
                }
                this.json = jsonFile;
                fos.close();
            }
        }
        zip.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

}
}

It takes those files and puts them into two directories, from which i read them in again using FileReadingMessageSource. I also would like to solve this using only annotation based notation, not xml.