Dynamically creating a query based on params being passed to a controller

Question

In my task management application, users should be able to filter tasks based on : assignedTo, priority, status and/or dueDate

I am not sure on how to create a dynamic query in that it will build a query based on the available parameters.

For example :

If I have a URL such as : task/index?assignedTo=1&status=2

I can build a query based on only these two parameters. The method I am used to is the

Task.findAllByAssignedToAndStatus(
   User.get(params.assignedTo),
   TaskStatus.get(params.status)
)

I obviously dont want to implement a DRY method by writing out each findAllBy query for every possible URL parameter combination.

Is there a good way to do this in grails?

Answer 1

I managed to get this working using createCriteria as follows :

I am using the value 0 for any of the params if the user selects 'All' for that particular filter, therefore it will be omitted from the where clause, ie no eq() statement for that parameter.

A snippet of the code:

else
    {       
        def assignedTo = Integer.parseInt(taskParams.assignedTo)
        def priority = Integer.parseInt(taskParams.priority)
        def status = Integer.parseInt(taskParams.status)

        tasks = Task.createCriteria().list {            

            eq("project", Project.get(taskParams.PId))

            if(assignedTo > 0)
                eq("assignedTo", User.get(assignedTo))

            if(priority > 0)
                eq("priority", TaskPriority.get(priority))

            if(status > 0)
                eq("status", TaskStatus.get(status))                
        }           
    }
    return tasks
}