检索表单会话而不保存

Question

我正在尝试从程序的会话中检索数据。我的问题是我想检查某些东西是否已经存在或刚刚创建。因此，我想像这样检查会话：

//status if party exists or not
FacesContext context = FacesContext.getCurrentInstance();  
HttpServletRequest request = (HttpServletRequest)context.getExternalContext().getRequest();  
HttpSession httpSession = request.getSession(false);  
String i = (String) httpSession.getAttribute("create");
//in case of the party doesn't exists
if (i.equals(null)) {
    httpSession.setAttribute("create", "1"); //I never used a set before for this value
    homeBean.getParty().setOrgKey(generateKey("org"));
    homeBean.getParty().setGastKey(generateKey("gast"));
    insertParty();          
}
else {
    updateParty();
}

我总是有NullPointerException.是否有可能解决这个问题？

Answer 1

好的，这里是解决方案。

这段代码以某种方式工作。我不知道为什么，但它有效，这就是我想要的一切:D

public void createParty() {
    // status ob die party existiert wird aus der session geholt
    FacesContext context = FacesContext.getCurrentInstance();
    HttpServletRequest request = (HttpServletRequest) context
            .getExternalContext().getRequest();
    HttpSession httpSession = request.getSession(false);
    if (httpSession.getAttribute("create") == null) {
        httpSession.setAttribute("create", 1);
        homeBean.getParty().setOrgKey(generateKey("org"));
        homeBean.getParty().setGastKey(generateKey("gast"));
        insertParty();
    } else {
        int i = (Integer) httpSession.getAttribute("create");
        if (i == 1) {
            updateParty();
        }
    }
}

就像有人说我应该检查 httpSession 是否为空

博士

OP equals()改为==，所以i null

你是巨魔吧？:D几乎就像每个软件开发者一样

好吧，但现在看起来像这样

//this method has to be called before createParty()
    public String cvParty() {
        party = new Party();
        FacesContext context = FacesContext.getCurrentInstance();
        HttpServletRequest request = (HttpServletRequest) context
                .getExternalContext().getRequest();
        HttpSession httpSession = request.getSession(false);
        httpSession.setAttribute("create", 0);
        return "partyDetail?faces-redirect=true&i=2";
    }

---

public void createParty() {
    // status ob die party existiert wird aus der session geholt
    FacesContext context = FacesContext.getCurrentInstance();
    HttpServletRequest request = (HttpServletRequest) context
            .getExternalContext().getRequest();
    HttpSession httpSession = request.getSession(false);
    if ((Integer) httpSession.getAttribute("create") == 1) {
        updateParty();
    }
    else {
        httpSession.setAttribute("create", 1);
        homeBean.getParty().setOrgKey(generateKey("org"));
        homeBean.getParty().setGastKey(generateKey("gast"));
        insertParty();
    }
}