Im really new to Grails and I try to understand how it works. I did some tutorials and wrote a sample application with a mysql database connection. Ive got three tables and therefor three domain-classes and three controller using def scaffold = true. So the views are generated automatically. Now I can add and remove and ... the data in my tables. Thats working.
But now I dont know how to go on. I mean, creating those tables and filling them is nice and its nice that this is possible so fast, but... Now I really want develope an application! Normally I work with Spring Framework, Spring Security, Spring MVC and so on to generate web applications. There, everything is logical. I have the requests comming in, the mapping to controllers, classes which work on the requests, answers given back, jsps rendered.... logical!
In Grails, I dont even know where to start for a real application! All tutorials I find show the same: Setting up those tables and being able to fill them, nice, nice - but after that?
Where do I save the "main.gsp". Do I need a controller for it? How does the application at start up redirect to "main.gsp".
Where can I define the "real logic" - I want to develope something like a "questions with multiple answers - try to select the correct answers"-application. Well, I must admit, I really dont know where to start. And I don't see the use of the Controllers and the possibility to add Data to my tables in my application. Thats for admins but not for users.
Could anyone give me an hint how to go on? Or maybe someone knows a good tutorial which is not about "setting up domain classes, controllers with scaffold, adding data to your database" - I dont see so much sense in it.
Thanks for your help! :-)
[EDIT] Thanks for the answers! Services, that was exactly what I was looking for. I guess I simply must get more familiar with it. The tutorials were just confusing me, but now I understand better!
If you are familiar with Spring and Spring MVC, the concepts in grails should be no surprise to you. Grails actually uses Spring MVC under the covers.
Grails can auto-generate Domain classes, controllers and views as you have tried in tutorials. This is to give you a starting point for your application. This is often enough for those textbook tutorials. For real applications though, you may not always have 1 domain class to 1 controller to 1 set of views. You might not always be doing CRUD operations on that domain. For this, you need to dig a bit deeper into Grails. You can do everything you previously have done in Spring MVC in Grails!
Here are some links to help you get going.
If you are trying to understand the 'flow' better. How requests get mapped to controllers/views, check out the UrlMappings.groovy in your config directory. Docs on that are located here: URLMappings
If you are trying to understand controllers better, check out this: Controllers. Keep in mind that your controller do not need to work on domain models. That is simply the default convention. They work similar to a Spring MVC controller.
Models are simple in Grails. Typically the controllers just return a map of the items you want to return. In Spring MVC, you often create a Model object, most times in Grails you will return something like [name: bean1, name2: bean2]. This allows you to easily get those two beans in the vies.
Start with 'Grails In Action'. The first chapter would give you details about the CRUD Sample app creation , but on reading further you would understand the grails flow better. Services are to be used for the logic, Controllers are used for delegation. You dont need explicit xml mapping as is done in Struts, Spring because everything here works on Convention.
Here is info on controllers: Controllers
Also you can use the same manual to find information on other stuff. For example about where to put business logic you should read in The Service Layer chapter.
Read Beginning Groovy, Grails and Griffon by Vishal Layka, Christopher M. Judd, Joseph Faisal Nusairat and Jim Shingler. They are building a real web application throughout the book with models, database access, authentication, css, templates and layouts, and many other things.
Related
I've been searching all day for an answer to my problem, and don't seem to be able to find an answer.
I'm trying to implement a CRUD web application using Grails, with the IntelliIDEA IDE. Whereas with JSF i could use primefaces which allowed me to do this with general ease, i am disappointed to see, or at least seems to be that way, that the framework is a step backwards when it comes to development of html pages.
All i want is to have a table that is populated from data that is coming from a controller, and whenever i add a record it is also displayed in this table. I want to be able to edit any record on this table and also remove records. It would be awesome if there could be a component like primefaces datatables that allows me to do this easily, without having to use JavaScript. I've taken a look to the Dojo plugin, but it's so outdated and incomprehensible to me that i have discarded this option, mainly because there is no documentation on the site on how to use it with Grails, specifically.
Also, i do not want to use scaffolding. I am trying to learn how to do this from scratch, and it is of my understanding that it doesn't work too well with domains with many to many relationship, for example.
In a nutshell, what I am looking for is the best way to make a CRUD application on Grails that doesn't involve the use of scaffolding.
I would suggest you to go through "Grails in Action" book and follow the creation of web application "Quote of the Day" and "Hubbub", don't use scaffolding instead create your own views and controller using documentation provided.
This will help you to understand basic CRUD operations in Grails.
And also looking into documentation http://grails.github.io/grails-doc/latest/guide/theWebLayer.html
See if this can help you.
You are aware that the scaffolding also can generate code for you to learn from and continue your work from there (i.e. it doesn't have to happen magically behind the curtains). I would say that is the typical means of starting out with Grails and CRUD.
Otherwise, no Dojo probably won't help you out a lot. Maybe have a look at some other plugin, for instance the Easygrid plugin? It is based on Javascript though, which most solutions do.
The "Grails in Action" recommendation is probably your best bet for the long-term, learning it from the pro's rather than learning-by-doing/top-to-bottom CRUD-style.
I'm new to Grails and web development. I started doing a project on Schedule management website stuff. I came across the Service concept that is provided by Grails. I understood the concept, but still I have confusion on when to use services.
For example, I need to implement a search module, where the manager can search for a user to find his schedules. In this case it will be good to implement it as a controller or as a service?
So,
When and where should I use Service?
To add to Grooveek's answer;
It is also nice to use Services to keep your Controllers nice and clean.
So Views just render data to the screen, Domain objects store state, Controllers route the user around the application, and Services perform the work.
I don't have enough reputation to comment on an answer or vote up so I have to provide an answer that really should be a comment. Anyways...
+1 on #tim_yates answer. Gotta love thin controllers. 2 things that I would add to the description of a controller:
Would be to translate parameters from the browser before hitting a service (e.g. Date, number, etc.)
Would be to translate data returned from services into something consumable for the views.
For me, ideally, services would never deal with translating a String parameter to it's inherent type. Or deal with building a model to be displayed on a view.
What and where I should use Service?
When you want your controller do to something that may be reused by other controllers
In our application we're doing a functional separation of service. We have a CorePersistanceService, which provides method to create, delete, update and manipulate Core Domain Classes (core for us).
I think persistance services are a good way to reuse GORM code throughout Grails code. You can create method in domain classes, but I don't like that, it's way less maintanable I think
We have a PDFService class for our PDF creation, a SolrService which connect to Solr, a Statisticservice that gather all our methods which collects statictics on our datas
Services in Grails are a manner to gather methods around a particular functional theme, in order to give possibility to reuse them in controllers (I forgot to mention our SecurityService, which is a pretty good Cross-Applications Example)
I recently started reading about ASP.net MVC and after getting excited about the concept, i started to migrate all my webform project to MVC but i am having a hard time keeping my controller skinny even after following all the good advices out there (or maybe i just don't get it ... ).
The website i deal with has Articles, Videos, Quotes ... and each of these entities have categories, comments, images that can be associated with it. I am using Linq to sql for database operations and for each of these Entities, i have a Repository, and for each repository, i create a service to be used in the controller.
so i have -
ArticleRepository
ArticleCategoryRepository
ArticleCommentRepository
and the corresponding service
ArticleService
ArticleCategoryService ...
you see the picture.
The problem i have is that i have one controller for article,category and comment because i thought that having ArticleController handle all of that might make sense, but now i have to pass all of the services needed to the Controller constructor. So i would like to know what it is that i am doing wrong. Are my services not designed properly? should i create Bigger service to encapsulate smaller services and use them in my controller? or should i have an articleCategory Controller and an articleComment Controller?
A page viewed by the user is made of all of that, thee article to be viewed,the comments associated with it, a listing of the categories to witch it applies ... how can i efficiently break down the controller to keep it "skinny" and solve my headache?
Thank you!
I hope my question is not too long to be read ...
This is the side effect of following the Single Responsibility Pattern. If each class is designed for only one purpose, then you're going to end up with a lot of classes. This is a good thing. Don't be afraid of it. It will make your life a lot easier in the long run when it comes to swapping out components as well as debugging which components of your system aren't working.
Personally, I prefer putting more of my domain logic in the actual domain entities (e.g. article.AddComment(comment) instead of articleCommentService.AddComment(article, comment)), but your approach is perfectly fine as well.
I think you are headed in the right direction. The question is how to instantiate your services? I'm no MVC.NET guru, but have done plenty of service oriented Java projects and exactly the pattern you are discussing.
In Java land we would usually use Spring to inject singleton beans.
1) You can do the same thing in .NET, using dependency injection frameworks.
2) You can instantiate services as needed in the method, if they are lightweight enough.
3) You can create static service members in each controller as long as you write them to be threadsafe, to reduce object churn. This is the approach I use in many cases.
4) You can even create a simple, global service factory that all controllers access, which could simply be a class of singletons.
Do some Googling on .NET dependency injection as well.
When you start creating an application or site in ASP.NET MVC, what do you do before typing in that first line of code?
I'm personally fond of creating a new ASP.NET MVC Web Application project and then cleaning out controllers/views until I have what is essentially a blank project (i.e. it runs but doesn't offer functionality). Then I start working on my model and adding controllers/views as needed.
I've also read about starter kits and sample applications but I have not yet started actively working with any of them. However, in my reading I have seen authors suggest that it might be good to start off with an existing template and build on it.
I'm trying to determine if there are better ways of starting off a project such that time is saved and/or the resulting deliverable is of higher quality.
The other things I do (I also clear out the controller/views etc)
Put an IOC in place.
Put ELMAH into the project.
Then I grab a coffee and write my first test.
Kindness,
Dan
PS: At some point I shall get around to creating a template for this so I don't redo it everytime. As soon as I decide upon my favourite IOC. :-)
I usually clear out the Content folder as well and put in place a nice CSS reset file and/or a CSS framework like the 960 grid
Before starting any type of project you must know what you want to do. So take a sheet of paper and start writing on here:
The name of your application
Enumerate the features
Make a quick draft of the domain model (entities that you are going to have)
Try finding the ways (choosing a technology) you are going to do different stuff like: data access, validation (client and server side), logging, IoC, Security, Caching etc.
Do a quick draft of all the views you are going to have in your application
Identify any other problems you might need to solve/implement/develop and think how are you going to do that
I'm currently working on an asp.net-mvc content management system. It would be incredibly useful to be able to deploy nested applications e.g. /shop to have a separate app inside. Or even another instance of the cms.
I've found some information around talking about limiting the inheritance of the web.config but I've no idea how this maps to an MVC application. I'm hoping as its essentially the same stack it will just run. Nothing is ever that easy though.
If anyone has any experience doing this I would be really grateful. The idea of one big application to rule them all is not at all nice.
Si.
To be honest you biggest hurdle is going to be creating the routes and making sure they don't interfere with routes already in the system. After you get that working the rest is easy as pie.
The first thing you will need is an HttpModule that will be inserted in to the web.config under the . This module will be used to register and custom ViewEngines or Routes that you want to register. You do this in the same way that you do in the Global.asax but instead of putting them in the Application_Start you put them in the static constructor of the HttpModule. This is so they are only loaded once like Application_Start.
By do the above you will have created a module that is easily transportable and doesn't require the implimentor to modify their Global.asax code to get your stuff to work.
The second thing you probably want to do is create a custom configuration in the web.config to set stuff like the root path of your application. This will be prepended on to the route when you are setting it up in the HttpModule. Also you can use this to store customization information that is not appropriate for the database.
Last but not necessary is that you may want to create a custom ViewEngine that knowns and understands your folder structure. This is only necessary if you want to store the views in a different path than the default views, in order to minimize conflicts.
Check out the Grouping Controllers with ASP.NET MVC from Phil Haack.
Hope it helps,
Bruno Figueiredo
I've gone down this road before (with /blog), but found it to be doable but complicated and difficult to maintain. Instead I ended up using subdomains:
www.example.com
shop.example.com
blog.example.com
These are much easier to maintain because you can just have them work as separate websites in IIS. And, of course, you can always redirect www.example.com/shop to shop.example.com.