Lesson 2: Create a simple multi-project build

Prerequisites

Java 16+
Gradle (install from gradle.org/install)

Step-by-step instructions

create new directory gradle-multi-project-masterclass
cd into new directory
run gradle init
accept all defaults except question 2. Choose Kotlin.
open project in IDE (I recommend IntelliJ IDEA)

add 2 plugins to build.gradle.kts build script

plugins {
    java
    id("org.springframework.boot") version "2.6.4"
}

add Spring Boot dependency to build script

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-web:2.6.4")
}

add Maven Central repository to build script
```
repositories {
    mavenCentral()
}
```
click Load Gradle Changes in IntelliJ IDEA
create directories src/main/java

create MaxiRailApplication.java in src/main/java/com/tomgregory/maxirail

package com.tomgregory.maxirail;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class MaxiRailApplication {
    public static void main(String[] args) {
        SpringApplication.run(MaxiRailApplication.class);
    }
}

create MaxiRailController.java in src/main/java/com/tomgregory/maxirail/controller

package com.tomgregory.maxirail.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MaxiRailController {
    @GetMapping(path = "/")
    public String getTimes() {
        return "No train times available right now :(";
    }
}

run application with ./gradlew bootRun
access application at localhost:8080

Cool! You now have a working single-project build.
create app subproject directory
copy src and build.gradle.kts into app
in settings.gradle.kts add the following line to include the app subproject
```
include("app")
```
check project still runs with ./gradlew bootRun
view project structure with ./gradlew projects
click Load Gradle Changes again for IntelliJ IDEA to pick up new multi-project structure

Congrats! You now have a multi-project build.

GitHub repository

The gradle-multi-project-masterclass repository contains the final code solution for lessons 2-5.