public String modify() {
    Paper paper = paperManager.getById(id);
    paper.setPaperName(paperName);
    paper.setPaperAttribute(paperAttribute);
    paper.setPaperAuthor(paperAuthor);
    paper.setNote(note);

    paperManager.modify(paper);

    return SUCCESS;
  }
  public String addPaper() {

    Paper paper = new Paper();
    paper.setPaperName(paperName);
    paper.setPaperAttribute(paperAttribute);
    paper.setPaperAuthor(paperAuthor);
    paper.setNote(note);

    paperManager.save(paper);

    return SUCCESS;
  }