CODEWITHSUNDEEP
grailsdependency-injection
Jonathan Lee
Jonathan Lee

Reputation: 13

"Cannot invoke method on null object" when injecting service into a controller

I have created a brand new Grails 4.0.0 app and created a domain / controller using the grails cmd. I've also created a simple service that returns "Hello World" to the controller, which then renders this to the screen. However I get "Cannot invoke method on null object" when trying to call the service method - seems like the dependency injection isn't working properly.

I've tried declaring the service using "def", I've also tried declaring by class name - neither of which seem to work.

package uk.org.pmms

import grails.gorm.transactions.Transactional

@Transactional
class HelloWorldService {

    def hello() {
        return "Hello World"
    }
}

package uk.org.pmms

class ClientController {

    //static scaffold = Client

    def helloWorld

        def show(Long id){
          Client clientInstance = Client.get(id)
          respond ("client": clientInstance, "message": helloWorld.hello())
        }
    }

I expect the controller to return the clientInstance data and a string "Hello World" which are displayed on a GSP page.

When I remove the "message:" part of the respond statement it displays the client information correctly so it is definitely just the service call that is the problem.

Upvotes: 1

Views: 1543

Answers (1)

erichelgeson
erichelgeson

Reputation: 2320

The name of the bean created for your service would be helloWorldService

class ClientController {

    def helloWorldService // <--- corrected bean name for auto wire by name.

    def show(Long id){
      Client clientInstance = Client.get(id)
      respond ("client": clientInstance, "message": helloWorldService.hello())
    }
}

Upvotes: 0

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