Top 30+ Java Grails Interview Questions Answers [ Aug 2022]

Java Grails Interview Questions Answers
Developer(s):Graeme Rocher
License:Apache License 2.0
Initial Release:October, 2005
Platform:Cross-platform (JVM)
Stable Release:5.1.6 / 31 March 2022; 3 months ago

Developing an application using a framework can be an intensive task, but with skills and experience, it will feel much easier. However, attending an interview is even worse, especially if you don’t know what to expect from the interviewing panel. There is no need to panic if you can go through the common Java Grails s Interview Questions and answer them. 

1.     What are Java Grails? 


It’s a web framework designed to boost development productivity. Apps coded using Java Grails can easily be updated using existing schema before their launch. It archives this possibility by using build-in domain migrations or mappers. This framework pairs with JVM, thus enabling the productivity of developers while still offering top-notch features like compile-time meta-programming, run-time & domain-specific languages, and asynchronous programming

2.     Java Grails s is written in which language?

The language used in java Grails is designed for the java platform and enhances the developers’ productivity. It’s a dynamic and optionally-typed programming language even though it has both static typing and compiling capabilities. 

3.     What is GORM?

It’s Grails s object-relational mapping implementation, among the best and most promising hibernate frameworks. It’s not only straightforward but also easy to learn. 

4.     Who developed Java Grails s?

David Heinemeier Hansson 

Developed Java Grails framework to promote the app development industry.  

5.     Differentiate between interactive modes, shell, and Grails s console

  • Grails s console: defined as a swing-based command consoler that’s the same as a groovy console. It allows users to run codes on an environment having access to domain classes. Through Grails console, developers also get to test their codes that are intended for use in the service and controllers. 
  • Grails interactive: this is the interactive part of Grails s CLI and allows developers to use script runner to execute gain scripts one after another.
  • Grails s shell: it’s a version of Grails s console and is mainly useful in the instances where the code needs to be accessed and tested on a remote SSH-based server. Grails s shell doesn’t reload with changes in domain class, making it best for long-running scripts. 

6.     Differentiate between run-war and run-app

Run-war complies and builds war files it obtains from the embedded containers. On the other hand, run-app runs the apps from the compiled source within the file system. The run-app reflects changes on other views controllers. It, therefore, implies that if you run the scripts during the application packaging, it will not be done at the run-app time. 

7.     Can you create a custom script in Java Grails s?

Yes, but to do so, you’ll need to call the Grails s function “create script myPasckage.myScript“.  This command creates a Gant script file in the script directory. It’s this filer that you can now run using Grails s my-script. Call Grails s create-script myPackage.myScript . This will create a new Gant script file under the scripts directory that you can then run via Grails s my-script.

8.     What are dynamic finders?

Java Grails s automatically creates methods based on domain class properties/specifications. These methods are what we call dynamic finders, and they allow alternative methods of querying domain classes.  

9.     Differentiate between HQL query, criteria, and dynamic finder

Even though all three are used for querying domain objects, each off then also performs a unique task. For instance

· Dynamic finders are of the form findAllByName(“Stephen”) added to the domain classes

  • HQL: a query language similar to SQL accepts that it’s fully object-oriented.
  • Criteria: they are DSL-based on groovy builders and hibernate criteria and are similar to c { like(“name,” “Stephen“) }

10. What are Java Grails s command objects?

An intermediate domain object not stored on the database is called a Grails s command object. It’s useful in scenarios where the developer intends to update a subgroup of properties from our domain objects. Data binding and data validation are both supported by the command objects. As a result, they can be useful for updating dater entered into forms. 

11. Does save () and validate() mean the same thing to you?

No, there are two different commands used to perform different tasks. Validate() runs validation commands and identifies errors, while save() ensures the objects are persisted. 

12. Explain the idea of externalized configuration in Java Grails s

Externalized configuration enables a developer to define .properties and .config file that doesn’t live in the Grails s-app/conf directory. This is done by defining the location from which the app will search for config files using Grails s. Config.location command with the filesystem/classpath. It popularly uses or enables configuration alterations without a need to recreate a new war file. 

13. Can you edit web.xml files?

Yes, but the template files must be generated through the Grails s install templates command. You can access web.xml files in the src/templates/war directory. The second option for editing the web.xml file is to create plugins and then remove or add nodes using the doWithWebDescriptor method

14. What is closure as used in Java Grails s?

It’s a short anonymous code block spanning a few code lines. In the method, the developer can enter a block of code as a parameter./ generally, closures are anonymous. They could be a variable at the stage where the closer is defined. When closure is used as a method, then it offers 

· findAll()

· Collect ()

· find()

· any() and every()

15. Define Metaprogramming

It’s the ability of groovy to add new variables or methods to class dynamically during run time and without affecting the source code. 

16. What are constraints? 

Constraints define the rules used in the validation of domain objects. The app developer defines the constraints under static constraints enclosure. Example of constraints includes email, blank and nullable. 

17. What’s the Events.groovy file?

It’s a file that defines the event hooks that the device call when Grails s scripts fire events

18. What is the role of the removeFrom() function?

A and b can have a one-many relationship, and when you use the removeFrom() function, it will rescind the backreference between the two variables. It could be a reverse of the addTo() method in the domain object. 

19.  Which constraints affect display?

· Widget: this constraint will affect the display play in that it ensures the field to display in the text area

· Display: it’s a constraint “none” hides the constraints and won’t be shown

20. What are named queries?

They are aliases coded from criteria builder DSL and allow the developers to re-use the queries. Named queries are normally put in namedQueries static property domain. 

21. What constraints affect database generation?

  • Nullable: the data schema marks the column nullable for a true value
  • Unique: The column index will be marked unique when the value I true
  • maxSize: it defines the field length as per the number keyed

22. What practices should be adhered to when developing Grails s applications?

It’s very straightforward to build mobile and web apps using the Java Grails s framework. Hiovwre, the developer must follow strict measures to ensure optimal performance and secure and safe applications.  Below is a list of practices you need to adhere to.

  • Controllers: you need a simple controller logic, and you should avoid duplicating the code
  • Services: this is a good choice for your courses-gained code. However, these services are transactional.
  • Views: you should maintain a consistent look when developing your application, and it should have a simple view but not too complex. 
  • Internalization: You should move text messages in the app view to the “”
  • Domain: every specific logic should be within its domain

23. What is scaffolding?

Scaffolding generates CRUD interfaces for domain classes. It features necessary views and controller actions for code creation, update, reading, and deletion of CRUD operation. Static scaffolding and dynamic scaffolding are the major types of scaffolding. 

24. When you call Grails s bug-report, what happens? 

Java Grails s generates a dehydrated timestamped minimal zipped file which you can attach to JIRA reports. When you call Grails s upgrade on the files, you’ll be able to hydrate the files. 

25. Which environments are available in Java Grails s? 

There are three defaults environments in Grails s, i.e., Test, development (dev), and Production (prod)

26. What are Explain Gorm events?

These methods can be inserted onto the domain objects but are only executed before/after saving domain objects in the databases. There are two Gorm events, i.e., afterDelete and beforeInsert

27. What is a different option available to dbCreate?

  • create-drop: destroy the database and creates a new one
  • create: create a new database only if there isn’t one
  • update: changes the database while keeping existing data and creating a new database if there isn’t any

28. How many parameters can there be in a dynamic finder?

The maximum parameters can only be 3

29. What are the key features of Java Grails s?

  • Asynchronous programming
  • Compile-time meta-programming
  • Run-time
  • Domain-specific languages

30. Grails s and groovy, are they similar?

Grails s was initially referred to as Groovy on Grails s, and it’s a programming framework inspired by ruby on rails. They are both highly productive and intend to promote coding by convention.


With the list of 30 common Java Grails s Interview questions, you will face the interviewing panel majestically and courageous. Because you’ll be well informed, however, you must go through each of them to increase the chance of you succeeding in the interview.

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