Spring：将带有数据的对象从控制器传递到jsp，并从Spring Form Submit取回预先保存的数据

Question

I am sorry if the title sounds confusing, I am a Spring newbie.

I have a controller class called AdController and I pass an Ad object to jsp in ModelAndView:

    ModelAndView laView = new ModelAndView("/ad/adAdd3");
    Ad laAd = new Ad();
    laAd.setPrice(100);
    model.put("ad", laAd);

In my adCreate.jsp, I allow user to add more info about this Ad except the price. And use a to submit the Ad object to the backend, my Controller class:

 <form:form modelAttribute="ad" method="post" class="form-horizontal" id="add-ad-form">

The problem is that on the back end, I received everything that's added by the user except price. Should I be getting the price data from the form submit? Am I missing anything?

Thanks!

Answer 1

Spring MVC is stateless, so in your controller you get only what is sent from the client. You need to include the price in the form for it to be sent to the server (you can make the field hidden to prevent the user from changing it). However, this will not prevent someone from manually sending the price with all other data (one just needs to change html code a little), so you need to handle this on the server side as well.

Answer 2

Spring MVC creates a new instance of your Ad object based upon the parameters in the request. So if the price value doesn't have a HTML input in the generated form then the value won't be populated in this new instance.

You can use the <form:hidden path="price"/> tag to pass the value back from the form.

If you look at the source of the HTML page you should see that this adds <input type="hidden" name="price" value="100"/> to the page.