I created a custom view that uses Json.Simple to serialize the model and write the JSON to the response directly.
For some requests, I need to send back a static JSON message, so I am wondering can I reuse a View instance I created earlier (with the message already set)?
My View class is thread-safe.
Sure. As long as you make sure it's thread-safe, as you say, there's no reason that your controller can't return the same View object multiple times. Unorthodox, but valid.
I do not see any problem in reusing an already created view since the render method gets current response object.
Related
If i use the MVC pattern to create my Spring project, is it wrong to call the Controller from the View?
Is this schema right?:
View calls the Controller
Controller performs operations and put data result into the Model
View reads data from the Model
Edit:
In my index jsp there is a menu with several categories of articles. I want to pass the name of the category to the controller. The controller calls the method of a beans which executes a query and returns the list of articles presents into the database.The Controller puts this list into the model and the View read this list from the Model.
Thanks
What you say (in your comments) is not specially wrong, but it does not make sense.
Either the categories are known when you build the view, and then it is the controller role to collate all information and put it into the model before calling the view with the model.
Or the category is chosen through a user interaction. But at this moment, the JSP is over for a long time : the response has been committed and transmitted to the browser. The only possibility is to prepare a new request (with a form or with ajax), send this new request to the server, where it will be handled by a controller, which will collate data into a (new) model and pass it all to a view
Depends what you mean by calling. But yes, View doesn't know anything about the controllers. It sends HttpRequests, and than the mechanism doing what you describe kicks in. There's the famous schema from spring docs, basically your bullets described via diagram. The point with respect to your question is that the view doesn't call the controller rather sends the request
I think you will find your answers in article mentioned below :
http://docs.spring.io/spring-framework/docs/2.5.3/reference/mvc.html
I have the action contlrSaveText() in controller and the method modelSaveText() in model.
When the data comes from the website to the contlrSaveText(), I check whether the required information is received to save text, i.e. text name, text content etc. Then I call modelSaveText() to actually perform saving text. Do I need to validate data in this method as well or I can expect that controlled already did the job?
A model is only an abstract description, while a controller does the work.
Your model might have a controller on its own that take care of the data and updates the model. But that is technically a controller.
How he works with toward the outside, e.g. another controller that fills data in, is up to you how you define the interface. If your model uses relations or properties that require to be set up by the controller then you have to validate the data before inserting/accepting. But if not, then there is no point in validation and it can be skipped for performance reasons.
If you need to reject invalid data you have to think of a way how to tell the outside what whent wrong so it can respond to the error.
In your example I would go for validation, but that is just my opinion.
Checked the official ref, found a million ways to do things.
I guess I have 2 set of use cases.
1. return customized http response, basically I am responsible for filling in status code, response body(either XML or JSON or text).
2. return Model and View. view is a jsp page typically and fill in the view with data from modle.
My question is which is a better way to go? it possible to mix them together. In my first use set, is it possible to return a View? also is it possible to have both on them in one method. something like if A return customized http response, if B return ModelAndView.
Thanks!
The return value from any request handling method (i.e. on marked with the #RequestMapping annotation must either identify a view (that will generate the HTTP Response) or generate the HTTP Response itself.
Each handler method stands alone; by that I mean, you can return a view name from some handler methods and generate the HTTP Response in other handler methods.
Check out 15.3.2.3 Supported handler method arguments and return types in the Spring 3x reference document at http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/
As an option to generating the HTTP Response in the handler method, you could setup multiple view resolvers; one or more for normal view resolution (jsp pages, tiles, etc.) and one or more for "special" view resolution (XML, JSON, etc.). For the "special" views, you may want to create your own view class that extends org.springframework.web.servlet.view.AbstractView.
You can accomplish something similar to what you are describing using the ContentNegotiatingViewResolver, which can deal with serving different content based on a request, with no changes required to your #RequestMapping annotations, or in fact anything in you're controllers.
There are plenty of resources on how to use this method, including this and this
I have created a create view within my MVC 2.0 Application and by default it included a field for the integer ID Column.
This is definitely a field i do not need.
If i remove the field and use updatemodel when trying to create the object in code, will something break because it doesnt see my ID column data being passed in, even though it is auto increment?
Also, i noticed that in the NerdDinner example, updatemodel was used and after that the repository.save method was called.
I thought that updatemodel would save the object to the database..why then call the .save method afterwards? Or have i missed something?
Any help with this would be appreciated.
Cheers
As I understand it, the UpdateModel method will blow away all data in the object. This is because MVC is round-trip based. Anything that goes out should come back if you need to keep state. See this question for more details.
A better way to handle this scenario in my opinion is to have an input model class as an Action parameter which is passed to a service call to update the domain entity in the DB. (Or this mapping code could be right in the action method if you really want.)
Also please be aware of the security vulnerabilities that could be introduced by binding directly to your DB model.
I'm just learning MVC so you could find my question rather strange...
My Controller have access to different shared objects through Container object passed to Controller's constructor. To access shared objects I should do $this->container->db to access Database adapter or $this->container->memcache to access Memcached adapter. I want to know should I put View object into Container with shared objects or no?
From one side it is really comfortable to take view from this container, but this way I couldn't create multiple Views instances (for example, every time I'm calling Controller's method from View I should have one more View instance). What is the solution? How should I pass View object into Controller and/or how should I create new View instances from Controller?
Thank you!
If you want that DI experience, do it on views as well, but I don't know if it really helps you anyway. Never call controller methods from views. Instead write some partial view methods and call them from views, which define the page layout (something similar to what Rails does).
IMHO if you want to get on MVC gradually, start from core principles and iteratively get to details, but don't learn architectural/design pattern as MVC by parts - architecture, design, the whole matters:)
Hmm, maybe try implementing caching for static parts. IMHO try inserting cacher object (through DI) to controller, and let that object decide if you want to send cached partial view or instantiate a new one. If you want to cache data from db, use the same pattern from controller towards models, so whenever in a controller you need models, ask db cacher object (same DI principle). Is it clear enough?