Grails - How to fine tweak events/actions?

I'm very new to Grails so pardon me, what I want to do may be very obvious to others. It will help me understand Grails and how the underlying magic works (or not work). Answers must be in Groovy/Grails, no javascript since I understand how javascript wor开发者_JAVA技巧ks.

Say I have the files:

User.groovy
UserController.groovy

I'm using scaffolding to CRUD the records in the USER table. Now I want to tweak it a bit.

in file User.groovy:

class User {
    String name
    static constraints = {
        name blank: false
    }
}

I want UserController.groovy(Is this the file I should edit?) to check if the submitted username is Bill, then automatically replace username with William then continue to create record in database.

In the web form I type in the name field: Bill and click SUBMIT

After the database is updated, I check the record and the username should be William in the USER table database.

Question #1 (Basic) How can I do this?

Now for something a bit trickier, what if after the William record is created in db#1, and I want to connect to a different db#2 and insert William in the USER table there?

So when I click SUBMIT once, both records will be inserted in 2 different databases almost simultaneously? What this action would do is insert the record in db#1 then connect to db#2 and then do the same insert in serial.

Question #2 (Intermediate) Where do I look in the Grails folders/files to modify this action behavior?

---

You have to create view which is associated with your controller. In that view, you have to create form, that will enable users to enter username, something like this:

<g:form controller="user" action="save">
    <g:textField name="username"/>
    <g:submitButton name="save" value="save"/>
</g:form> 

Now when user sumbits the form, save action of user controller is invoked. All parameters that where passed to controller action is being held in params map. So in your save action, you can access username like this:

def save = {
        def user = new User(username: params.username)
        // OR
        def user = new User(params)
        // you can change username like so
        user.username = "William"

        user.save()
    }

This is very quick example, I advise you to study documentation and some tutorials maybe which will give you more knowledge of all the concepts and tools that Grails provides for you.

With writing user to two databases there is a slight problem. Grails doesn't provide ability to have multiple databases connected to your app out of the box. There is a plugin, called Datasources which allows you to define multiple data sources in your application, but the drawback is that you have to define which domain classes are connected to which data source. Thus you can't have a user domain class for your primary database and secondary, you have to create two domain classes, one for each data source.

---

I'll just answer the basic :)

Yup, you can do it in UserController.groovy. Say, you have this form:

<g:form action="someAction" method="post">
    <input type="text" name="name" ... />
    ...
</g:form>

In the controller, you can have an action like this (there are multiple possible approaches):

def someAction = {
    def nameVar = params.name // get the text this way

    // process nameVar here
}

As for the database access... depends how you want to approach it. Grails suggests that you do something like:

User theUser = //get the user
theUser.name = //the value
theUser.save(flush:true)

However, I've encountered time and again some issues with Hibernate so I don't always use that approach. Instead, I do the usual Java-like programming like:

...
theUser.executeUpdate("UPDATE <table_name> ...")
theUser.save(flush: true)
...

Then just select from the database

...
User.executeQuery("SELECT ...")
...

Hope this helps ;)

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For Q#1 you should modify the save function in your controller. There you can check the parameters for a specific username or modify the new created user object as you like.

For Q#2 i reccomend you to have a look at the Datasources plugin

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Q1: This is really a job for GORM Hibernate events as it involves business logic constraint for you domain.

beforeInsert(){
  this.name = "William"
}

Q2: Using multiple data sources is integrated in Grails 2.0. No need for the plugin.