how to retrive attached file saved in database in grails platform, and mongoDb database

Question

i am using mongoDB database to store data, and grails project.

i am able to save uploaded file in database but i am not able to makeout how to fetch that attachment from database and show to user as 'attachment' : which onclick can be downloaded.

i am attaching my code to save my uploaded file. please suggest to solve my problem.

controller code :

def save_task()
{
        def task = new Task()
        bindData(task, params, [except:"task_attachment"])
        task.project_id= session.id_of_project
        task.employee_id = params.int('employee_id')
        def file = request.getFile('task_attachment')
        task.task_status_percentage = 0
        task.task_attachment = file.getBytes()
        task.save()
        task.errors.allErrors.each { println it }           
        session.task_list.add(task)
}