DDevelopment & Design

All field constructor in Groovy

TupleConstructor annotation in Groovy generate constructors for class with each of its properties (eventually also fields). The class below@TupleConstructor(includeFields = true)class Person {   String firstName   String lastName&nb…

TupleConstructor annotation in Groovy generate constructors for class with each of its properties (eventually also fields). The class below

@TupleConstructor(includeFields = true)
class Person {
   String firstName
   String lastName
   private boolean male
}

will have constructors: Person(), Persion(String), Person(String, String) and Person(String, String, boolean). You could test it using code below.

class TupleConstructorTest extends GroovyTestCase{
    @Test
    void testSimpleTupleConstructorShouldGenerateConstructor() {
        assertScript '''
            import groovy.transform.TupleConstructor
            @TupleConstructor(includeFields = true)
            class Person {
                private final String firstName
                private final String lastName
                private final boolean male
                String toString(){ "$firstName $lastName $male" }
            }            
            assert Person.constructors.size() == 4
            assert new Person().toString() == 'null null false'
            assert new Person('John').toString() == 'John null false'
            assert new Person('John','Smith').toString() == 'John Smith false'
            assert new Person('John','Smith', true).toString() == 'John Smith true'
        '''
    }
}

I almost always create classes with all private final fields and generate constructior with all fields using my IDE.

So I have prepared new transformation AllFieldConstructor which bases on TupleConstructor and generates only constructor with all fields as parameters.

class AllFieldConstructorTest extends GroovyTestCase{
    @Test
    void testSimpleTupleConstructorShouldGenerateConstructor() {
        assertScript '''
            import com.blogspot.przybyszd.transformations.AllFieldConstructor
            @AllFieldConstructor
            class Person {
                private final String firstName
                private final String lastName
                private final boolean male
                String toString(){ "$firstName $lastName $male" }
            }
            assert Person.constructors.size() == 1
            assert new Person('John','Smith', true).toString() == 'John Smith true'
        '''
    }
}

The sources are available here

— Previous article

Git aliases for better Gerrit usage

Next article —

Restart or power off Rasperry PI with REST call

You May Also Like
DDevelopment & Design

Simple trick to DRY your Grails controller

Grails controllers are not very DRY. It's easy to find duplicated code fragments in default generated controller. Take a look at code sample below. It is duplicated four times in show, edit, update and delete actions:

class BookController {
def show() {
def bookInstance = Book.get(params.id)
if (!bookInstance) {
flash.message = message(code: 'default.not.found.message', args: [message(code: 'book.label', default: 'Book'), params.id])
redirect(action: "list")
return
        }
        [bookInstance: bookInstance]
    }
}

Why is it duplicated?

There is a reason for that duplication, though. If you move this snippet to a method, it can redirect to "list" action, but it can't prevent controller from further execution. After you call redirect, response status changes to 302, but after method exits, controller still runs subsequent code.

Solution

At TouK we've implemented a simple trick to resolve that situation:

  1. wrap everything with a simple withStoppingOnRender method,
  2. whenever you want to render or redirect AND stop controller execution - throw EndRenderingException.

We call it Big Return - return from a method and return from a controller at once. Here is how it works:

class BookController {
def show(Long id) {
withStoppingOnRender {
Book bookInstance = Book.get(id)
validateInstanceExists(bookInstance)
            [bookInstance: bookInstance]
        }
    }

protected Object withStoppingOnRender(Closure closure) {
try {
return closure.call()
        } catch (EndRenderingException e) {}
    }

private void validateInstanceExists(Book instance) {
if (!instance) {
flash.message = message(code: 'default.not.found.message', args: [message(code: 'book.label', default: 'Book'), params.id])
redirect(action: "list")
throw new EndRenderingException()
        }
    }
}

class EndRenderingException extends RuntimeException {}

Example usage

For simple CRUD controllers, you can use this solution and create some BaseController class for your controllers. We use withStoppingOnRender in every controller so code doesn't look like a spaghetti, we follow DRY principle and code is self-documented. Win-win-win! Here is a more complex example:

class DealerController {
@Transactional
def update() {
withStoppingOnRender {
Dealer dealerInstance = Dealer.get(params.id)
validateInstanceExists(dealerInstance)
validateAccountInExternalService(dealerInstance)
checkIfInstanceWasConcurrentlyModified(dealerInstance, params.version)
            dealerInstance.properties = params
saveUpdatedInstance(dealerInstance)
redirectToAfterUpdate(dealerInstance)
        }
    }
}