Developing webapplications with grails - no idea how it really works

Question

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!

Answer 1

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.