Is there any java library (maybe poi?) which allows to merge docx files? [closed]

With POI my solution is:

public static void merge(InputStream src1, InputStream src2, OutputStream dest) throws Exception {
    OPCPackage src1Package = OPCPackage.open(src1);
    OPCPackage src2Package = OPCPackage.open(src2);
    XWPFDocument src1Document = new XWPFDocument(src1Package);        
    CTBody src1Body = src1Document.getDocument().getBody();
    XWPFDocument src2Document = new XWPFDocument(src2Package);
    CTBody src2Body = src2Document.getDocument().getBody();        
    appendBody(src1Body, src2Body);
    src1Document.write(dest);
}

private static void appendBody(CTBody src, CTBody append) throws Exception {
    XmlOptions optionsOuter = new XmlOptions();
    optionsOuter.setSaveOuter();
    String appendString = append.xmlText(optionsOuter);
    String srcString = src.xmlText();
    String prefix = srcString.substring(0,srcString.indexOf(">")+1);
    String mainPart = srcString.substring(srcString.indexOf(">")+1,srcString.lastIndexOf("<"));
    String sufix = srcString.substring( srcString.lastIndexOf("<") );
    String addPart = appendString.substring(appendString.indexOf(">") + 1, appendString.lastIndexOf("<"));
    CTBody makeBody = CTBody.Factory.parse(prefix+mainPart+addPart+sufix);
    src.set(makeBody);
}

With Docx4j my solution is:

public class MergeDocx {
    private static long chunk = 0;
    private static final String CONTENT_TYPE = "application/vnd.openxmlformats-officedocument.wordprocessingml.document";

    public void mergeDocx(InputStream s1, InputStream s2, OutputStream os) throws Exception {
        WordprocessingMLPackage target = WordprocessingMLPackage.load(s1);
        insertDocx(target.getMainDocumentPart(), IOUtils.toByteArray(s2));
        SaveToZipFile saver = new SaveToZipFile(target);
        saver.save(os);
    }

    private static void insertDocx(MainDocumentPart main, byte[] bytes) throws Exception {
            AlternativeFormatInputPart afiPart = new AlternativeFormatInputPart(new PartName("/part" + (chunk++) + ".docx"));
            afiPart.setContentType(new ContentType(CONTENT_TYPE));
            afiPart.setBinaryData(bytes);
            Relationship altChunkRel = main.addTargetPart(afiPart);

            CTAltChunk chunk = Context.getWmlObjectFactory().createCTAltChunk();
            chunk.setId(altChunkRel.getId());

            main.addObject(chunk);
    }
}