Kotlin + Spring + Vue: Migration from Maven to Gradle

Let's look how to migrate our current Maven Project to Gradle.

Actually, there is an instruction Moving from Maven to Gradle in under 5 minutes, but hardly the result will be what you really need. I recommend perform this process manually - it takes not much more time.

First of all, you need to install Gradle.

Basic algorithm for subprojects - backend and frontend

#1 Remove all maven files - pom.xml, .mvn, etc.
#2 Go to backend subproject using command line.
#3 Run gradle init and answer the following questions:

Select type of project to generate: basic
Select implementation language: Kotlin
Select build script DSL: let it be also Kotlin

#4 Remove settings.gradle.kts - this file is needed only for root project.
#5 Run gradle wrapper

Basic algorithm for root project

The algorithm for root project is the same except one thing: don't delete settings.gradle.kts.

Build Configuration

Backend

Let's fill build.gradle.kts in the backend project with the following code:

Specify all required Kotlin and Spring plugins
Please, don't forget about org.jetbrains.kotlin.plugin.jpa plugin to use database connection successfully
Specify all required dependencies
Add runtimeOnly(project(":frontend")) dependency - we need to build frontend first

Frontend

Let's fill build.gradle.kts in the frontend project with the following code:

Let's use org.siouan.frontend plugin for frontend building
Specify Node.js version, clean script, build script and assemble script - in our case these are commands specified in package.json
Now we pack our frontеnd subproject to JAR file and use it as a dependency, so we have to specify task which copies files from build directory to /public and creates a JAR after assembling

Modify vue.config.js: specify the new build directory outputDir: 'build/dist'.

Modify package.json: specify the build script: "build": "vue-cli-service build" or make sure that it's already specified.

Root Project

We don't need to add anything to build.gradle.kts in our root project, but we need to add the following code to settings.gradle.kts:

Here we specified the name of the project and subprojects.

Build and Run

Now we can build our project. Let's go to root folder and execute:

./gradlew build

NOTE: if use have placeholders in your application.properties such like ${SPRING_DATASOURCE_URL} but don't have the relevant environment variables the building will be failed. Use ./gradlew build -x test to avoid this.

Make sure, that the order of build is frontend than backend. Also you can see at your project structure by

gradle -q projects

You should see:


Root project 'demo'

+--- Project ':backend'

\--- Project ':frontend'

And now we are able to run our app:

./gradlew bootRun

.gitignore

Let's look at the files and folders we should add to .gitignore:

backend/build/ - same for frontend
build - same for root projects
.gradle

NOTE: don't add gradle folder and gradlew files to .gitignore - they contains nothing dangerous and required for successful build at the remote server (Heroku, for example).

Ways to improve

Configure a CI/CD pipeline for automated build and deploy

vaadim

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