Question

I have a User class like this:

package com.grailsinaction

class User {
    String userId
    String password;
    Date dateCreated
    Profile profile
    static hasMany = [posts : Post]
        static constraints = {
        userId(size:3..20, unique:true)
        password(size:6..8, validator : { passwd,user ->
                            passwd!=user.userId
                        })
        dateCreated()
        profile(nullable:true)
        }
    static mapping = {
        profile lazy:false
    }
}

Post class like this:

package com.grailsinaction

class Post {
    String content
    Date dateCreated;
    static constraints = {
    content(blank:false)
    }
    static belongsTo = [user:User]
}

And I write an integration test like this:

//other code goes here
void testAccessingPost() {
        def user = new User(userId:'anto',password:'adsds').save()
        user.addToPosts(new Post(content:"First"))
        def foundUser = User.get(user.id)
        def postname = foundUser.posts.collect { it.content }
        assertEquals(['First'], postname.sort())
    }

And I run using grails test-app -integration, then I get a error like this :

Cannot invoke method addToPosts() on null object
java.lang.NullPointerException: Cannot invoke method addToPosts() on null object
    at com.grailsinaction.PostIntegrationTests.testAccessingPost(PostIntegrationTests.groovy:23

Where I went wrong?

Answer 1

My guess is that the save() method is returning null. Try this instead:

def user = new User(userId:'anto',password:'adsds')
user.save() // Do you even need this?
user.addToPosts(new Post(content:"First"))

According to the documentation:

The save method returns null if validation failed and the instance was not saved and the instance itself if successful.

So it’s possible that you should be looking at what’s going wrong in validation… do you need to specify that some of the fields are optional, for example? (I’m not a Grails developer – just trying to give you some ideas.)