Framework

Java / Spring Boot

Spring Boot applications built with Maven and run on Eclipse Temurin JRE 21.

Container port8080

Requirements

pom.xml in the repo root

DropDeploy uses Maven (mvn package) to build. Gradle is not yet supported.

Spring Boot with embedded Tomcat

The JAR must be self-executable. Standard Spring Boot starters include this.

App listens on port 8080

Spring Boot defaults to 8080. Do not change server.port unless you also update the Dockerfile.

Demo app

A minimal app that is ready to push and deploy. Copy the files below into a new repository, commit, and deploy — it should go live without any changes.

Quickstart

Go to start.spring.io — select Maven, Java 21, add Spring Web dependency, and download.

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
                             https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.3.0</version>
  </parent>

  <groupId>com.example</groupId>
  <artifactId>demo</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>demo</name>

  <properties>
    <java.version>21</java.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>

src/main/java/com/example/demo/DemoApplication.java

package com.example.demo;

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

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

src/main/java/com/example/demo/HelloController.java

package com.example.demo;

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

@RestController
public class HelloController {

    @GetMapping("/")
    public String hello() {
        return """
            <html>
              <body style="font-family:system-ui;display:flex;justify-content:center;
                           align-items:center;min-height:100vh;margin:0;
                           background:#0f172a;color:#f1f5f9">
                <div style="text-align:center">
                  <h1 style="color:#ef4444">Hello from DropDeploy!</h1>
                  <p style="color:#94a3b8">Spring Boot app is live.</p>
                </div>
              </body>
            </html>
            """;
    }

    @GetMapping("/api/health")
    public java.util.Map<String, String> health() {
        return java.util.Map.of("status", "ok");
    }
}

Use start.spring.io for the fastest setup. The pom.xml above is a minimal working alternative if you prefer to build from scratch.

Build & start commands

DropDeploy runs these steps inside the container when you click Deploy.

mvn dependency:go-offline -q
mvn package -DskipTests -q
java -jar target/*.jar

Environment variables

Set these in Project → Env Vars in the dashboard. Never commit secrets.

Variable	Required	Description
SPRING_DATASOURCE_URL	No	JDBC connection string (e.g. jdbc:postgresql://host:5432/db).
SPRING_DATASOURCE_USERNAME	No	Database username.
SPRING_DATASOURCE_PASSWORD	No	Database password — always via env var.
SERVER_PORT	No	Defaults to 8080. Change only if you update the Dockerfile accordingly.

Common issues

Build takes 5–10 minutes on first deploy

mvn dependency:go-offline downloads all deps. Docker caching makes future deploys faster.

Multiple JARs in target/

Maven outputs both the main JAR and original-*.jar. COPY target/*.jar fails if multiple exist. The spring-boot-maven-plugin should produce just one executable JAR by default.

Tests failing during build

DropDeploy passes -DskipTests so tests do not run. Run tests locally before deploying.

Rust