My setup is pretty simple.
I have a Controller with a get- and a postmethod. The getmethod fills a Model which is then used to render a thymeleaftemplate of an HTML-form.
When the User clicks submit the formdata will be posted to the postmethod. This method then performes some businesslogic which may have two outcomes.
First possibilty: Everything works well and a redirect to the getmethod is performed.
Second Possibility: An exception occurs. In that case the user shall be presented with the same form he submitted containing the data he tried to submit. So in that case my postmethod returns the identifying String of the same template as the getmethod. But thymeleaf tells me that the model is lacking some attributes.
Why doesn't spring inject the same model in the postmethod that has been used to render the template of the getmethod.
Is there any way, to recycle the model from the getcall in the postmethod?
I usually redirect after a post method by using the RedirectAttributes. It is used to add data to the model even in a redirect.
This is an example of how to use it:
#PostMapping("/course")
public String addCourse(#RequestParam("course") Course course, RedirectAttributes redirectAttributes) {
// show a popup that the `account.name` has been added
redirectAttrs
.addAttribute("course", course)
.addFlashAttribute("message", "Course created!");
return "redirect:/courseOverview";
}
Related
I am trying to build sth pretty simple, but I try to do it the correct way. But I struggle to figure out what is best.
I have a process chain where the user has to fill in some fields in different forms. Sometimes it depends from the user inputs which form the user is shown next.
[HttpGet]
public IActionResult Form1(Form1Vm f1vm)
{
return View(f1vm);
}
[HttpPost]
[ActionName("Form1")]
public IActionResult Form1Post(Form1Vm f1vm)
{
//process the data etc
//prepare the new viewmodel for the next form view (f2vm)
//Option1:
return View("Form2", f2vm);
//Option2:
return RedirectToAction("Form2", f2vm);
//for Option 2 I would need an additional HttpGet Action Method in which I
//would have to call Modelstate.Clear(); in order to not have the
//immediate validation errors on page load
//also all the properties of my viewmodel are passed as get parameters
//what looks pretty nasty for me
}
//More form views action methods should be added here...:
What is the better way? As mentioned in my comments above I have quite a big disadvantage for using the RedirectToAction option. However if I use the direct View(); call, I don't take care on https://en.wikipedia.org/wiki/Post/Redirect/Get and the user cannot simply refresh a page without getting a warning that his form is submitted once again.
Do I miss another way or don't see something obvious?
Edit: I just thought about a 3rd way, which I have seen quite often: Not transfering the whole VM to a HttpGet method but only the ID. I'd then have to load all the data stored previously directly from the db, map it again to my new VM and then call the View(); with this VM. Right now I think this is the "best" solution, however I feel like it is pretty laborious...
As per the dicussions, I would suggest using depending on your preference :
1) Save to db at the end of each form post and as you suggested use the I'd to redirect to a GET.
2) Depending on the the number of form pages and your requirements, retrieving values that a form needs on the get would be standard practice. This ensures that if a user drops off a form at any stage you can then start them off where they left off.
3) I wouldn't setup the viewmodel for the next form in the post of the previous. Generally as part of the single responsibility principle you want to ensure that your methods have only one reason to change.
4) PostRedirectGet pattern should be implemented with this to ensure data is not saved multiple times if a user refreshes after a post.
Disclaimer: I wished I had a through understanding before starting working with the framework.
But as it is of now, I'm lacking on that front, and hence the question.
I am working with Spring-Portlet MVC.
I have a flow, where in I take an input on a screen, validate the input, depending upon its result it either render same screen or next screen.
Implementation detail:
I have an action method which takes form backed command object. It checks whether entered input is valid or not. If it is not valid, it populate error message in BindingResult instance it takes as another argument.
We have different render method, to render different screen.
I'm taking command object as an argument in these render method. This command object I'm receiving is same as one passed to action.
Problem:
While rerendering a screen spring-mvc should bind the error message populated in action method. Currently when I take command object as argument in render method spring-mvc is somehow unable to bind that error message. But interesting enough it is able to bind the error message if I don't take command object as argument in render method and rather create a new command object altogether there.
can,some one having better understanding of spring-portlet mvc please explain this behaviour, or tell where I am lacking in understanding.
Regards,
Mawia
EDIT: Just to enrich the below answer: Though I didn't exactly isolated the issue which was causing the said behaviour, but the way I met my requirement was using modelattribute. ModelAttribute can be used either on method or a parameter to a method. It ensures that model will made available to all the call till the view is render(that is my understanding!). So we don't need to take command object as parameter in Render method, just annotate the commandObject parameter in action method with ModelAttribute and then you can get the same object returned from model as suggested in the answer below.
I don't think the command/model object should be an argument/parameter in the render method. I have had the same issue trying to get the validation error messages when command/model is defined as argument in render method signature. I typically have the command/object creation/populate in a separate method, like this:
#ModelAttribute(value="address")
public Address getAddress(#RequestParam Integer id){
Address address = null;
if(id != null){
address = myService.getAddress(id);
}else{
address = new Address();
}
return address;
}
If I still need to access the ModelAttribute/command object from the render method, I typically get it by:
#RenderMapping
public String showAddressPage(ModelMap modelMap){
Address address = modelMap.get("address");
//make any additional changes to address
}
I used this example as reference article
I'm having difficulty grasping the concept of MVC within .NET. I'm creating a basic Blog application, mainly to gain insight and skills with MVC. I just don't quite get some of it. The part I am currently unclear about is the relationship between a Controller and View. It would clear the matter up if someone would answer me this.
I have a View called TestA which corresponds to my Controller ControllerTestA. Now I've added the following inside the ControllerTestA.
public ActionResult TestA (){ //do something }
Now I need to know if all my postbacks in whatever form from view TestA will have to go through my TestA Controller method. So essentially I could have different postback with different parameters for different reasons. Some in use with one postback and others in use for another. Is that how it is done?
Would love some assistance here.
You are missing a crucial part of the relationship here, which is routing. You are speaking in terms of WebForms using terms like Postback; don't do that because you'll end up confusing yourself.
The best way to think about MVC is in Requests and Responses.
Let's look at how a request (high level) happens in an MVC application.
Request
Request hits the server with a url ex. /hello/world
That url is used to match any entries in your route table
When a match is found, that route defines basic values like what controller and action should be called.
The controller is created, and that action is called with the route values and other request properties (querystring, session, etc...).
Response
We are now in the controller action, run the code you need to fulfill the request
Pass the data to the View
The view is determined by convention and your ViewEngine
The view is then rendered and written to the response.
The request/response is finished.
Note
This whole process is determined by the route, and the relationship between the controller and view are trivial. Where the form is posted to is determined by you in the view by using helper methods that determine what route to hit in the next request/response flow.
Some Helper Methods.
#Url.Action("index", "home");
#Html.ActionLink("index", "home")
#using (Html.BeginForm("create", "home")) { }
To sum it all up, the relationship between the controller action and view is really facilitate by your routes. Once you have a grasp of how to create them, then you will better understand how to manage the interaction of your application. Hope that helps. :)
There is no such thing as "Postback" in MVC. In contrast to WebForms, a view only renders HTML to be sent to the browser. As soon as any type of request is issued by the browser, it goes to the controller, not to the view.
As for the relationships:
If you define a TestAController (note: Not "ControllerTestA"), it serves the "/TestA/*" URL's. If you have a method TestA in there it will serve "/TestA/TestA".
If your method returns View(someModel) it will look for a view named TestA.cshtml/TestA.aspx, named like your method, within a folder Views\TestA (named like your controller, without the "Controller" suffix)
The view will render the HTML based on the someModel passed by the controller.
Within the view you may call other URL's or post data to some. This closes the circle.
As for the parameters or overloads, there are some restrictions:
You can define overloads for GET vs. POST vs. PUT vs. DELETE. You will need to annotate the methods with the according attributes though.
However you cannot define multiple overloads of the same method name for POSTs with different sets of parameters. You will need to make your POST method signature such that parameters can or cannot be sent to the server:
Example:
public ActionResult TestA(
string someOptionalParameter, int? someOtherOptionalParam)
{
if (string.IsNullOrEmpty(someOptionalParameter)) { ... }
if (someOtherOptionalParam == null) { ... }
}
The model-mapper will set your parameters to null if they are not posted to the server.
Like Khalid already mentioned - you should not mix up the concepts of MVC and WebForms. They are very different. MVC has no such thing as a "view state" which could be posted to the server. It has no WebForm-like lifecycle for the ASPX (or CSHTML) pages.
If you have a form in a view, then that form has a url to which it will post to. This URL is in the Html.BeginForm method in your view.
The form will then be posted to the appropriate controller methond in the approoriate controller
So if BeginForm starts like this:
using (Html.BeginForm("AddProduct", "Product"
Then the action method "AddProduct" in the controller Product (ProductController is the class name) will be called.
Im starting with MVC2 and i have a simple question:
If i have a typed view with a form inside, and this textbox created with lambda expressions:
<%: Html.TextBoxFor(e => e.Name)%>
When i submit this form the default model binder take the request form, takes the model typed to the view, serialize the data posted (as a this model) and pass it to an action of my controller.
To try to explain myself better, lets imagine that i have a url like localhost/edittestmodel/ID/1 and i have in my controller action the following code:
public ActionResult Edit(int id)
{
TestModel testmodel=new TestModel();
testmodel.Name="texttorenderintotextbox";
//whats the class that place the testmodel properties into the view?
return View(testmodel);
}
What's the responsable class for place the Name property of my testmodel object into the textbox
<%: Html.TextBoxFor(e => e.Name)%>
Thanks in advance.
Best Regards.
Jose.
It's the TextBoxFor helper method that's responsible for generating the input field from the lambda expression.
View's don't have anything to do in POST request and model binding
When you have strong type views, model type is barely used to have the simplicity of code intellisense in view's code (so you can use lambda expressions like in your example).
But when you POST data back, nothing gets checked against the view. It gets checked against controller action parameters though. And if there's a parameter with a certain custom model binder type, that particular model binder is used to process incoming data.
But to answer your question: TextBoxFor checks your strong type view's model and generates particular textbox with correct name attribute. So data from it will be posted back under the correct form field name.
To go even deeper. It's the view engine that parses view's ASPX code and runs all server side scripts including Html.TextBoxFor() call.
i wish to have a simple Action in my controller that accepts a few optional values and some integer values.
this is my route i wish to have:
HTTP.POST
/review/create
and this is the Action method i would like...
[AcceptVerbs(HttpVerbs.Post)]
public JsonResult Create(int userId,
int addressId,
byte baseScore,
byte reviewType,
string subject,
string description)
{ ... }
I'm under the uneducated impression that all of those arguments above will be populated by the forms collection values ... but it's not happening. Also, I have no idea how I would write a route, to handle those ... because those values are form post data....
here's my global.asax....
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
// Api - Search methods.
routes.MapRoute(
"Search Methods",
"{controller}/{action}"
);
In fact, the action method is never called because it doesn't seem to find it :(
But, if create and action without any of those arguments, then it finds it ?????????
How would you write a route and action method to accept some require and some optional arguments, for the route /review/create ?
As far as i can see you may rewrite your controller action like this:
public ActionResult Create(int foo, int bar, byte blah, string name, int? xxx) {
// code here
}
The ModelBinder will then ensure that foo,bar and blah are set. Name and xxx may be null. I can't test it a the moment, but i think return type of the action should be ActionResult.
If you are POST'ing a form, just make sure that the elements in your form (textboxes, checkboxes, textarea, etc) have id's that match the parameters in your method. As an alternative you can pass a FormCollection to the method, and do myFormCollection["foo"] to get a string representation of the value (which can then be parsed to an int).
From my experience, you are missing a number of key elements and concepts with this question.
First and foremost, I don't believe you can execute a POST without a form. The form has to contain the controls from which you pull the values that get passed to the controller method. If the goal is to simply unit test your POST controller method, then just call the method directly in your test, which it appears that you're doing, based on one of your comments. If you involve the view, then you're doing integration testing, not unit testing. Regardless of the test type, the test will always fail because you are choosing not to build the form. Even if you manage to force the POST using Fiddler, Firebug or any other mechanism, you're still not testing the view, you're testing the HTTP protocol.
I highly recommend that you employ a web application testing tool, such as WatiN or Selenium, to test your web pages, rather than throw together a quick-and-dirty test that really doesn't test anything useful.
In your post request set content-type="application/json; charset=UTF-8" and pass the values for the method parameter in JSON format. This should make Asp.MVC not to look in FormCollection for those values.