I've a small doubt. I use Spring SimpleFormController with a form backing object.
Let's say my formBackobject has the following member:
- Id
- Name
- Sex
on the jsp page, I only bind name and sex to input field. when i submit the form, the backend controller can remember the value of the id field and so can distinguish whether this is a "new" or "edit' mode.
Could you tell me the trick behind this?
Thanks,
In my opinion you need to override isEqual() and hashCode() function.
In my code I'm generating uuid and assign it to String and then implement isEqual() and hashCode() where I'm comparing these strings.
Such technique is very useful for Hibernate as well and it will assure you that you always generate unique object.
The 'trick' behind is that the form is kept in session. When you submit the form, only 'name' and 'sex' fields are overwritten and Id is left as it is.
It's logical to think that the id is saved in session. you're right. I don't submit the id value, but spring can auto load its value into the id field.
All this is done automatically behind the scene. And that's what caused my confusion since the first place.
Anyway, all of this are assumption made by you and me. It may not be true from the documentation.
Related
Spring MVC 4.1
Hi,
I have a situation where, on a single page, there are several input fields. As the users enters numbers into these fields, a bunch of calculations will occur and update various other fields on the page.
I want this whole calculation model to take place in Java on the server-side. I really want to avoid replicating this logic in Javascript on the client.
What I envision is...
User opens the page, the object that does the calculations (let's call it Calculator) is created and its initial state is set (many of its fields are pre-populated with values).
This Calculator instance is stored and available for the duration of the user's time on that page.
Whenever the user changes a value in an input field, that new value is sent to the server via ajax and plugged into our Calculator object. The Calculator, re-calculates the other fields based on the new state and returns the results to the page.
The other fields on the page are updated accordingly.
The key here is that I'm not sending the state of all fields with each ajax request. I'm only sending the current value that was updated. Essentially, I'm trying to ensure that the form state and the Calculator state on the back-end are always synchronized.
I have looked into #SessionAttributes and #ModelAttribute.
The problem with #ModelAttribute, as I understand it, is that it will be re-created with each ajax request.
The problem with #SessionAttributes is that it is a session variable. What if the user has two of these windows open? And how do I ensure the object is removed from the session when they leave the page? etc...
Maybe there's no magic Spring bullet and I just have to figure out the session variable thing. But any pointers on dealing with this would be much appreciated.
Thanks!
You have a couple of options:
.1. Like you have said using the #SessionAttributes, however yes it suffers from the issue that you have mentioned, multiple instances of the same session will see the same variable.
.2. Store state somewhere else and re-hydrate the state using #ModelAttribute annotated method. I would personally prefer this approach, essentially when you create the form, create it with a identifier for the current state:
#RequestMapping(params = "form")
public String createForm(Model uiModel) {
uiModel.addAttribute("calculationId", UUID.randomUUID().toString());
return "calculationpage/create";
}
Then for subsequent ajax requests, ensure your previous calculationId is sent across:
#ModelAttribute("calculationState")
public CalculationState rehydrateState(String calculationId) {
//retrieve current state of calculation from some persistent store..
}
#RequestMapping("/calculate")
public String handleCalculation(#ModelAttribute("calculationState") CalculationState c) {
//you will get a calculationstate with the delta's at this point..
}
.3. Another potential approach may be to use session but disambiguate different instances within the session with a custom id:
public String handleCalculation(HttpSession session, #RequestParam("calcId") String calcId) {
CalculationState calcState = (CalculationState) session.getAttribute("calculation" + calcId);
}
You need any sort of persistent store outside session to store and retrieve the state of your calculator model. Like Biju said, I will go for solutions like No 2.
I'm asking what is the best strategy for filtering with Symfony2.
I want to filter a table of entities (hotels). This filter should allow me to :
choose hotels with or whitout email, with or without web site etc.
choose hotels based on state and/or city (relation OneToMany)
choose what information I want to display on the table with checkboxs (for example display "email adress" on the hotel table, but do not display "tel" or "web site").
First I think to build the filter form on the HotelController. When the filter is submitted, I had a FlashBag for every $_POST sended, redirect to the same page, and if there are FlashBag I send cookies to the $reponse. Then I display the table filtered with data who are on the cookie.
But I dont't really like this, cause I had a very big indexAction() on the HotelController, and I think it'as not really clean to change $_POST to FlasBag to Cookie, is it ? I do this redirection, cause by refreshing the page, data are not posted again.
I'm also asking a question, to prevent a too big IndexAction() method, can I put some code to another method, for exemple a method PostToFlashBag() and another FlashBagToCookie(), or every method on a Controller has to end with the word "Action" and must be accessible with the router ?
Then, I think to another thing : had an entity "Filter", with every row I need. For exemple "WithEmail", "DisplayTel" etc.. Then I can build a FilterType easily, and update the Filter entitie, to redirect to the same page (again, to prevent reposting data if the user refreshes the page). Finally, I can display the table with the object Filter, with a method on the HotelRepository.
That seems great, but I'm a little worry because the filter entity will only have one entry, and I have to find the Filter(1). Due to MVC, is it correct to have a model with only one entry ?
What strategy would you choose (maybe another one) ? I'm interesting to learn good practice with MVC and Symfony2 devloppemnt.
Having a dedicated model class - let's call it Filter - that will receive the values input by the user, is definitely the way to go.
More over, use the Symfony2 form on this input, so you can have validation, and be sure that the withEmailis trully a boolean, etc. From you Filter, build you SQL/Doctrine query and return what your controller have to return, be it a view, or raw datas.
You can have any method you want in a controller. After all, controllers in Symfony2 are plain old PHP objects. They only have to implement ContainerAwareInterface. Usually they inherits Controller, but this inheritance only brings some proxy methods, like getDoctrine or render.
The only convention is that methods which are used as route must end with Action
I am sending over a series of array values from a posted form to an MVC3 Controller. I was hoping the default modelbinder would be able to parse this but I'm having some difficulty with it.
The array is in the following format:
order[0].[type]=some value.
I think this is the reason the model binder is not parsing my values because I'm not getting anything populated in my model.
What would be another way to handle this?
Probably need to post more of your code so I can see what you are doing exactly. However saying this you need to pass the model to the view/partial view on the response you are trying to retrieve on the post request.
If not you will have to iterate through the Form Collection that will be returned and the Actions Methods type e.g. ActionMethodName(FormCollection form), one issue is name versus id its the name of the Kendo UI control that is used to get the value not the id.
1As far as I remember the right format was:
orders[0].OrderID=13;
orders[0].Name="test";
orders[1].OrderID=15;
orders[1].Name="again test";
The indexing should start from 0 and increase by 1.
Check this out: http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx
I'm looking for a way to validate just a single field (object property) against the constraints specified in the annotations of a particular entity.
The goal is to send an AJAX request after the "onBlur" event of a form field, asking the server to validate this single field only, and - depending on the response - add a small "OK" image next to this field or an error message.
I don't want to validate the whole entity.
I wonder what's the best approach for this problem? Thanks for any tips.
The Validator class has the validateProperty method. You can use it like this:
$violations = $this->get('validator')->validateProperty($entity, 'propertyName');
if (count($violations)) {
// the property value is not valid
}
Or, if the value is not set in the entity, you can use the validatePropertyValue method:
$violations = $this->get('validator')->validatePropertyValue($entity, 'propertyName', $propertyValue);
if (count($violations)) {
// the property value is not valid
}
Have a look at validation groups. I think this is what you need. You could add a group "ajax" or and just adding the one constraint to it. Then tell the validator to use that group. THe symfony2 docs have an example included.
I've just been reading the article on MSDN about remote validation. This is great, but it only shows validating a specific property value.
Is there a way I can pass other values from my model into the validation for a particular property? For example, let's say that a user wants to cancel a number of items off an order - they should be prevented from entering a figure greater than the original order amount.
Thanks
No, you can't.
Brad Wilson:
At this time, only property level
validators can emit client-side
validation (as that lines up much
better with the idea of input
validation in the form of the
browser... there is no "model" to
speak of, from the browser's point of
view).
Stuart Leeks:
I don't believe you can hook up client
validation with IValidatableObject
Well, i am nit sure if you mean this, but you can use AdditionalFields with your RemoteValidation attribute.
Remote Validation in ASP.Net MVC 3: How to use AdditionalFields in Action Method