Building a REST API with Grails

REST API Design

Grails excels at building RESTful APIs. With the rest-api profile and built-in URL mappings, you can create a complete REST API in minutes.

Domain Class Setup

class Book {
    String title
    String author
    int pages

    static constraints = {
        title blank: false
        author blank: false
        pages min: 1
    }

    static mapping = {
        table 'books'
    }
}

REST Controller

class BookController extends RestfulController<Book> {

    static responseFormats = ['json', 'xml']

    BookController() {
        super(Book)
    }

    @Override
    def index() {
        respond Book.list(params)
    }

    @Override
    def show() {
        respond Book.get(params.id)
    }

    @Override
    def save() {
        def book = new Book(request.JSON)
        if (!book.save()) {
            respond book.errors, view: 'create'
            return
        }
        respond book, status: 201
    }
}

URL Mappings

class UrlMappings {
    static mappings = {
        "/api/books"(resources: "book")
        "/"(view: "/index")
        "500"(view: '/error')
    }
}

Testing the API

# Create a book
curl -X POST http://localhost:8080/api/books \
  -H "Content-Type: application/json" \
  -d '{"title":"Groovy","author":"Smith","pages":300}'

# List all books
curl http://localhost:8080/api/books

Key Points

• Use the rest-api profile for REST-only projects.
• RestfulController provides CRUD operations automatically.
• respond handles content negotiation (JSON/XML).
• resources in URL mappings creates RESTful routes.
• Request JSON binding works automatically.