(Quick Reference) ## params ### Purpose A mutable multi-dimensional map (hash) of request (CGI) parameters. ### Examples To obtain a request parameter called `id`:
    class BookController {
        def show() {
            def book = Book.get(params.id)
        }
    }
To perform data binding (see data binding in the user guide):
    def save() {
        def book = new Book(params) // bind request parameters onto properties of book
    }
### Description The standard Servlet API provides access to parameters with the `HttpServletRequest` object. Although Grails provides the same capability through the request object, it goes a bit further by providing a mutable map of request parameters called `params`. The `params` object can be indexed into using the array index operator or de-reference operator, so given the URL `/hello?foo=bar` you can access `foo` with
    println params.foo
The params object can also be used to bind request parameters onto the properties of a domain class using either the constructor or the properties property:
    def book = new Book(params)
    book = Book.get(1)
    book.properties = params
For further reading see data binding in the user guide. | Quick Reference (hide)