Create a Spring Boot Application

This quick start shows how to create a minimal Spring Boot web application with projen's Java project type.

Create the project

Create a new Java project:

mkdir hello-spring
cd hello-spring
pnpm dlx projen new java --group-id org.acme --artifact-id hello-spring

Spring Boot requires Java 17 or newer, so check your local Java version before continuing:

java -version

Configure Spring Boot

Edit src/test/java/projenrc.java to add Spring Boot, configure Java 17, and add a task for running the application:

import io.github.cdklabs.projen.java.JavaProject;
import io.github.cdklabs.projen.java.JavaProjectOptions;
import io.github.cdklabs.projen.java.MavenCompileOptions;

public class projenrc {
    public static void main(String[] args) {
        final String springBootVersion = "4.0.6";

        JavaProject project = new JavaProject(JavaProjectOptions.builder()
            .artifactId("hello-spring")
            .groupId("org.acme")
            .name("hello-spring")
            .version("0.1.0")
            .junit(false)
            .sample(false)
            .compileOptions(MavenCompileOptions.builder()
                .source("17")
                .target("17")
                .build())
            .build());

        project.addDependency("org.springframework.boot/spring-boot-starter-webmvc@" + springBootVersion);
        project.addTestDependency("org.springframework.boot/spring-boot-starter-webmvc-test@" + springBootVersion);
        project.addPlugin("org.springframework.boot/spring-boot-maven-plugin@" + springBootVersion);
        project.getTestTask().exec("mvn test");
        project.addTask("run").exec("mvn spring-boot:run");

        project.synth();
    }
}

Run projen to synthesize the Maven configuration:

pnpm dlx projen

The default projen JUnit component is disabled so Spring Boot's test starter can manage the test framework versions.

The initial Java project includes sample Java files. Remove src/main/java/org/acme/Main.java and src/test/java/org/acme/MyTest.java before adding the Spring Boot application.

Add application code

Create src/main/java/org/acme/HelloSpringApplication.java:

package org.acme;

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

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

Create src/main/java/org/acme/HelloController.java:

package org.acme;

import java.util.Map;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {
    @GetMapping("/")
    public Map<String, String> hello() {
        return Map.of("message", "Hello from Spring Boot and projen!");
    }
}

Create src/test/java/org/acme/HelloSpringApplicationTest.java:

package org.acme;

import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
class HelloSpringApplicationTest {
    @Test
    void contextLoads() {
    }
}

This smoke test verifies that the Spring application context starts successfully.

Build and run

Build the project:

pnpm dlx projen build

Start the application:

pnpm dlx projen run

In another terminal, call the endpoint:

curl http://localhost:8080

You should receive a JSON response:

{"message":"Hello from Spring Boot and projen!"}

Since projen synthesizes the project configuration, update src/test/java/projenrc.java and run pnpm dlx projen again whenever you need to change dependencies, plugins, tasks, or other generated files.