Grails命令对象默认值

Question

I am trying to use Grails Command Object to filter action parameters. But I want to set a default value if the parameter is not present in URL.

class ListCommand {

    String order = 'desc'
    String sort = 'startDate'

}

def list(ListCommand cmd) {
    println cmd.order
}

I thought the behaviour would be same as if I was creating a domain object. I don't want to handle each parameter in the action like:

cmd.order = params.order ?: 'desc'

Answer 1

if you always use such action declarations:

def list(ListCommand cmd) { ... }

or

def list = {ListCommand cmd -> ...}

you may try this:

class ListCommand {
    String order
    String sort

    def beforeValidate() {
        order = order ?: 'desc'
        sort = sort ?: 'startDate'
    }
}

because in those action definitions validate() method always calls for command objects.

Answer 2

I don't think you can set default values to command object fields.

I suggest that you create a service to initialize your command object with default values before binding your params:

def service

def action = {
    def listCommand = service.createListCommand() 
    bindData(listCommand, params)
}


class Service {
   def createListCommand() {
       def listCommand  = new ListCommand()
       initDefaultValues(listCommand)
       return listCommand
   }

def initDefaultValues(def listCommand){
        listCommand.order = 'desc'
        listCommand.sort = 'startDate'
    }
}