Running Java Spring Boot on pure Android phone or virtual device

"Pratique a linguagem de programação e o framework mais utilizado por grandes corporações somente com seu Smartphone Android e sem necessidade de alterar configurações avançadas como "root" ou instalação de aplicativos suspeitos."

Screencast at YouTube

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You will build a classic “Hello World!” endpoint which any browser can connect to. You can even tell it your name, and it will respond in a more friendly way.

• An Android phone or an Android Virtual Device (AVD)
• A command line Android app, I recommend Termux
• A Java™ Development Kit (JDK)
• Basic Linux command line knowledge 
• Will and curiosity

Use start.spring.io to create a “web” project. In the “Dependencies” dialog search for and add the “web” dependency as shown in the screenshot. Hit the “Generate” button, download the zip.

Locate the downloaded demo.zip file path.

Copy it to the home Termux folder

cd && cp /storage/emulated/0/Download/demo.zip demo.zip

Unzip it and go to the demo unzipped folder

unzip demo.zip && cd demo

Verify if you have Java installed on your system

java -version

If no, update your system and install it

apt update -y && apt upgrade -y && apt install openjdk-17-jdk

Remove the original file DemoApplication.java located at src/main/java/com/example/demo folder.

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

Now create and edit a new DemoApplication.java adding the code below

nano -l -A -S -m src/main/java/com/example/demo/DemoApplication.java

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class DemoApplication {

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

    @GetMapping("/hello")
    public String hello(@RequestParam(value = "name", defaultValue = "World") String name) {
        return String.format("Hello %s!", name);
    }
}

Save

CTRL + o

Exit

CTRL + x

./mvnw spring-boot:run

It will take some seconds to compile and show the results like this:

Open your browser and in the address bar at the top enter https://localhost:8080/hello .

You should get a nice friendly response like this:

What is displayed if you add ?name=HigorVaz to the end of the URL?

https://spring.io/quickstart

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