Spring MVC Model Attribute null - spring-mvc

I want do add an ID to a URL in my template:
#Controller
public class DashboardController {
#RequestMapping("/dashboard")
public String index(Model model){
model.addAttribute("provider_id", "1");
return "dashboard";
}
}
In my dashboard.html I want do display the ID.
<a th:href="#{'/cloudservice/' + ${provider_id}}">Show</a>
But the Generated URL is /cloudservice/null. Why isn't the 1 displayed that i put into the model?

I tested this out and I couldn't recreate this issue, this is working perfectly fine for me. Please share the complete controller code and your dependencies here.
One wild guess, your Model class is of type org.springframework.ui.Model, right?

you can use like this http://www.thymeleaf.org/doc/tutorials/2.1/usingthymeleaf.html#link-urls
<!-- Will produce '/gtvg/order/3/details' (plus rewriting) -->
view

Related

#model for _layout.cshtml on MVC4?

I was wondering if there's a way to specify a model for the _layout.cshtml file, i've seen lots of posts with the basic same question with people replying with "alternative" solutions, not saying it's not possible nor showing how exactly we could achieve this
having some experience with webforms I've been trying to migrate to MVC and often find myself with such questions, I've found this website: http://blog.bitdiff.com/2012/05/sharing-common-view-model-data-in.html
which partially solved my problem but even them don't bind their _layout.cshtml with a #model, as far as I know, I have to specify a model on each view if I want to access the SharedContext, please correct if I'm wrong
what I wanted to do is declare a "#model Namespace.MyModel" on _layout.cshtml so it could retrieve its information by itself, instead of having to implement a model for each view inherinting from the LayoutModel
*I hope I'm being clear, basically, I wanted to know how can I declare #model tag on a _layout.cshtml so it can access its own model
with the solution I linked before (even though it's not linked to my question) I have to do:
#(((BaseController)ViewContext.Controller).Context.Property) to get the shared information, and if I could simply declare (and use) a #model instead, I could accomplish the same thing by doing something like: #Model.Property*
as you can see, im struggling trying to migrate whatever I already know from webforms to MVC and it's being quite difficult for me since I have to adopt certain practices which are completely different from what I'm used to
thanks in advance
You should delegate the parts of your layout that "need a model" to a separate controller using partial views and RenderAction:
#Html.RenderAction("SomeAction", "LayoutController")
Have LayoutController.SomeAction return a PartialViewResult, which you can then strongly type to a model.
Even though you already accepted an answer, based on your saying you are just pulling an image URL you should do it using JQuery, not a model.
This code is untested, apologies for that. Feel free to point out if I typed a bug. The HTML element containing the background image has the id="url" attribute so the selectors work.
Controller
[HttpGet]
public string GetSessionUrl()
{
//logic to detmine url
return url;
}
JQuery
$(document).ready(function () {
var $url = $('#url');
var options = {
url: "/Home/GetSessionUrl",
type: "get",
async:false
};
$.ajax(options).done(function (data) {
$url.attr('src', data);
});
});
You can add BaseModel to _Layout.
#model BaseModel
Then all models inherit from that BaseModel class.
public class MyModel : BaseModel
{
}
As others stated, it is not a good practice. If your model forgets to inherit from BaseModel, it'll throws exception at run time. However, it is up to you.
In BaseController you can declare any model as property.
public class BaseController : Controller
{
public BaseController ()
{
MyTag = new TagModel (); // or get db, take any value from there
}
public TagModel MyTag { get; set; }
}
In action:
ViewBag.MyTag = MyTag ;
And in _Layout.cshtml, you can use
#{
var myTag = (TagModel)ViewBag.MyTag;
}

Why is my validation firing on the get request before the post in MVC3?

I have a MVC3 view that enables the user to create a couple different things. Within the parent view the forms to do so are broken up via jquery ui tabs like the following:
<div id="tabs">
<ul>
<li>New Thing 1</li>
<li>Different New Thing</li>
</ul>
<div id="tabs-1">#Html.Action("CreateNewThing", "NewThingController")</div>
<div id="tabs-2">#Html.Action("CreateDifferentThing", "DifferentThing")</div>
<div></div>
</div>
<script type="text/javascript">
$(function () {
$("#tabs").tabs();
});
</script>
Within the partial view I have:
#model NewThingViewModel
#using (Html.BeginForm("CreateNewThing", "NewThingController", FormMethod.Post, new { id = "frmCreateNewThing" }))
{
...
with input fields, a submit button, etc. This seems to work well: it renders everything and posts just fine to the right controller action method.
However I'm now wiring in the validation and I've got an issue.
In the controller it is rendering the view like so:
public ActionResult CreateNewThing(NewThingViewModel model)
{
... initializing model fields, drop downs etc.
return PartialView("CreateNewThing", model);
}
I have a seperate post method like so:
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult CreateNewThing(NewThingViewModel newThingViewModel, FormCollection collection)
{
.....
}
Sample Model:
public class NewThingViewModel
{
[Required]
[StringLength(50)]
[Display(Name = "Display Name:")]
public string DisplayName { get; set; }
}
The trouble is, when the page first comes up the fields marked as [Required] through DataAnnotations in the model are showing up red as well as the validation summary showing them invalid when the page initially shows. I.E. it's acting like it's already been posted before the user gets to enter anything on the initial load or even put anything in the text boxes.
I know the first non-post CreateNewThing is firing because I can catch it in the debugger and I know the 2nd one does not on the initial load.
What would cause my validations to fire on the Get?
Is it due to the way Html.Action works and the fact that I'm rendering partial views onto another view?
I'm using UnobtrusiveJavaScriptEnabled and ClientValidationEnabled = true in web.config.
I can't find anyone else that has run into this particular problem. Every other example just seems to work, then again I don't find an example where the view is broken into three partials contained within jquery ui tabs.
How do I fix this?
Options:
Do I need to manually manipulate the Model.IsValid as a workaround?
Use a different mechanism to render the partial views on the parent view instead of Html.Action?
Use some javascript/jquery to catch the validation and stop it?
Don't have method parameters on your GET controller action. You can initialize an empty model and pass it to the view but you dont need a model to be passed into the method
You're passing in an "empty" model (which I assume has default values set for your required properties), when you should be passing in null.

How can I run code from my layout file?

I used the following tutorial to help me build an RSS Reader in my ASP.NET MVC3 Razor application:
http://weblogs.asp.net/jalpeshpvadgama/archive/2011/08/17/creating-basic-rss-reader-in-asp-net-mvc-3.aspx
However, unlike the tutorial example, I want the RSS feed to be displayed on every page, and have therefore added it to my layout file, /Views/Shared/_Layout.cshtml
I currently only have 2 views on my site, and to get the RSS Reader to work on both views I've got the following code in my HomeController:
public class HomeController : Controller
{
//
// GET: /Index/
public ActionResult Index()
{
return View(CT.Models.RssReader.GetRssFeed());
}
public ActionResult About()
{
return View(CT.Models.RssReader.GetRssFeed());
}
}
From my WebForms experience, I would simply add the RSS Reader code in my master page code behind, and it would automatically work on every page.
Is there a Controller for layout pages which allows me to do the same?
How can I get this to work on every call of the layout page, without having to return anything?
EDIT: Following #Sebastian's advice, I've now added this code to a Partial View, removed CT.Models.RssReader.GetRssFeed() from return View() and included this in my layout file:
#Html.Partial("_MyPartialView")
The code in this partial view is:
<ul>
#foreach (var item in Model)
{
<li>
#item.Title
</li>
}
</ul>
However, I'm not getting a runtime error:
Object reference not set to an instance of an object.
It's erroring on the line #foreach (var item in Model)
You have to create a partial view and add functionality there.
Then in your layout, render this partial.
EDIT
Is your partial view really a partial view? The reason I said that is because you have "_" in front of the name which suggests that it might be a layout (might just be a naming convention).
To fix object reference error, you have to add the #Model declaration on top of your partial view.
Hope it helps.
UPDATE
In order to use different model in partial view, you need to explicitly declare which model you are going to use on render partialmethod.
#{Html.RenderPartial("../YourFeed", Model.YourFeedModel);}
Let me know if that resolved your issue.
The new error you are having is due to you not passing a Model to the partial view. You can do this with the second argument of the Html.Partial function...
Html.Partial("ViewName", MyModel);
As I think you are trying to do this in a Layout page you could also consider using a static reference to get your RSS feed. So forget about needing to pass in a Model and in your partial have:
#foreach (var item in RssRepository.GetFeed())
{
<li>
#item.Title
</li>
}
this like to a class something like...
public static RssRepository
{
public static MyModel GetFeed()
{
return new MyModel();//<- return what you would normally pass as a Model for RSS feeds
}
}
Hope that all makes sense

Create controller for partial view in ASP.NET MVC

How can I create an individual controller and model for a partial view? I want to be able to place this partial view any where on the site so it needs it's own controller. I am current rendering the partial as so
#Html.Partial("_Testimonials")
Why not use Html.RenderAction()?
Then you could put the following into any controller (even creating a new controller for it):
[ChildActionOnly]
public ActionResult MyActionThatGeneratesAPartial(string parameter1)
{
var model = repository.GetThingByParameter(parameter1);
var partialViewModel = new PartialViewModel(model);
return PartialView(partialViewModel);
}
Then you could create a new partial view and have your PartialViewModel be what it inherits from.
For Razor, the code block in the view would look like this:
#{ Html.RenderAction("Index", "Home"); }
For the WebFormsViewEngine, it would look like this:
<% Html.RenderAction("Index", "Home"); %>
It does not need its own controller. You can use
#Html.Partial("../ControllerName/_Testimonials.cshtml")
This allows you to render the partial from any page. Just make sure the relative path is correct.
If it were me, I would simply create a new Controller with a Single Action and then use RenderAction in place of Partial:
// Assuming the controller is named NewController
#{Html.RenderAction("ActionName",
"New",
new { routeValueOne = "SomeValue" });
}
The most important thing is, the action created must return partial view, see below.
public ActionResult _YourPartialViewSection()
{
return PartialView();
}
You don't need a controller and when using .Net 5 (MVC 6) you can render the partial view async
#await Html.PartialAsync("_LoginPartial")
or
#{await Html.RenderPartialAsync("PartialName");}
or if you are using .net core 2.1 > you can just use:
<partial name="Shared/_ProductPartial.cshtml"
for="Product" />
Html.Action is a poorly designed technology.
Because in your page Controller you can't receive the results of computation in your Partial Controller. Data flow is only Page Controller => Partial Controller.
To be closer to WebForm UserControl (*.ascx) you need to:
Create a page Model and a Partial Model
Place your Partial Model as a property in your page Model
In page's View use Html.EditorFor(m => m.MyPartialModel)
Create an appropriate Partial View
Create a class very similar to that Child Action Controller described here in answers many times. But it will be just a class (inherited from Object rather than from Controller). Let's name it as MyControllerPartial. MyControllerPartial will know only about Partial Model.
Use your MyControllerPartial in your page controller. Pass model.MyPartialModel to MyControllerPartial
Take care about proper prefix in your MyControllerPartial. Fox example: ModelState.AddError("MyPartialModel." + "SomeFieldName", "Error")
In MyControllerPartial you can make validation and implement other logics related to this Partial Model
In this situation you can use it like:
public class MyController : Controller
{
....
public MyController()
{
MyChildController = new MyControllerPartial(this.ViewData);
}
[HttpPost]
public ActionResult Index(MyPageViewModel model)
{
...
int childResult = MyChildController.ProcessSomething(model.MyPartialModel);
...
}
}
P.S.
In step 3 you can use Html.Partial("PartialViewName", Model.MyPartialModel, <clone_ViewData_with_prefix_MyPartialModel>). For more details see ASP.NET MVC partial views: input name prefixes

Html.ActionLink in Partial View

I am using the following code in my master page:
<% Html.RenderAction("RecentArticles","Article"); %>
where the RecentArticles Action (in ArticleController) is :
[ChildActionOnly]
public ActionResult RecentArticles()
{
var viewData = articleRepository.GetRecentArticles(3);
return PartialView(viewData);
}
and the code in my RecentArticles.ascx partial view :
<li class="title"><span><%= Html.ActionLink(article.Title, "ViewArticle", new { controller = "Article", id = article.ArticleID, path = article.Path })%></span></li>
The problem is that all the links of the articles (which is built in the partial view) lead to the same url- "~/Article/ViewArticle" .
I want each title link to lead to the specific article with the parameters like I'm setting in the partial view.
Thanks.
I think your not using the ActionLink correctly. Change the ActionLink code to:
Html.ActionLink(
article.Title,
"ViewArticle",
"Article", // put the controller here
new
{
id = article.ArticleID,
path = article.Path
},
null)
Notice the null at then end.
EDIT: Why are you using [ChildActionOnly] in your controller? Since it is an MVC 2 feature I am assuming that you are using MVC2? Try removing it and check out the following article:
http://www.davidhayden.me/2009/11/htmlaction-and-htmlrenderaction-in-aspnet-mvc-2.html
I think the issue has to do with your partial not rendering. I would start by just trying to verify that your partial is rendering properly. Once you confirm that start to debug why the partial is not outputing.
I was able to solve the problem by using the following call in my RecentArticles action:
return PartialView("~/Views/Shared/Article/RecentArticles.ascx", viewData);
It seems like the partial view was not being rendered at all,
Thanks !

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