How to Deploy Spring Boot Applications on NGINX on Ubuntu 16.04

What is Spring Boot?

Spring Boot enables quick development of the Spring Framework by taking care of default configurations and allowing Java developers to focus on rapid prototyping. This guide shows how to create a simple Spring Boot application which is then exposed through an NGINX reverse proxy.

Before You Begin

You will need a Linode with both Java 8 and NGINX. If these are already installed on your Linode, skip to the next section.

Install Java JDK 8

Install software-properties-common:

sudo apt install software-properties-common

Add the Oracle PPA repository:

sudo apt-add-repository ppa:webupd8team/java

Update your system:
```
sudo apt update
```
Install the Oracle JDK. To install the Java 9 JDK, change java8 to java9 in the command:
```
sudo apt install oracle-java8-installer
```
Check your Java version:
```
java -version
```

Install NGINX

These steps install NGINX Mainline on Ubuntu from NGINX Inc’s official repository. For other distributions, see the NGINX admin guide. For information on configuring NGINX for production environments, see our Getting Started with NGINX series.

Open /etc/apt/sources.list in a text editor and add the following line to the bottom. Replace CODENAME in this example with the codename of your Ubuntu release. For example, for Ubuntu 18.04, named Bionic Beaver, insert bionic in place of CODENAME below:
File: /etc/apt/sources.list
1
deb http://nginx.org/packages/mainline/ubuntu/ CODENAME nginx

Import the repository’s package signing key and add it to apt:

sudo wget http://nginx.org/keys/nginx_signing.key
sudo apt-key add nginx_signing.key

Install NGINX:
```
sudo apt update
sudo apt install nginx
```
Ensure NGINX is running and enabled to start automatically on reboot:
```
sudo systemctl start nginx
sudo systemctl enable nginx
```

Install Spring Boot CLI

The Spring Boot CLI makes creating a scaffold for a project much easier. SDKMAN! is a tool that simplifies installation of the Spring CLI and build tools such as Gradle or Maven. Using the Spring Boot CLI, a new project can be created directly from the command line.

Install dependencies for SDKMAN!:
```
sudo apt install unzip zip
```
Install SDKMAN!:
```
curl -s https://get.sdkman.io | bash
```
Follow the instructions printed on the console:
```
source "/home/username/.sdkman/bin/sdkman-init.sh"
```
Verify SDKMAN! is installed:
```
sdk help
```
Install Spring CLI:
```
sdk install springboot
```
Verify the installation:
```
spring version
```

Install Gradle:

sdk install gradle 4.5.1

Downloading: gradle 4.5.1

In progress...

######################################################################## 100.0%

Installing: gradle 4.5.1
Done installing!

Build a jar File

There are many build tools available. The Spring Boot CLI uses Maven by default but this guide will use Gradle instead. See this comparison for a discussion about the differences between Maven and Gradle.

Create a new project with the Spring Boot CLI. This creates a new directory called hello-world with a project scaffold.
```
spring init --build=gradle --dependencies=web --name=hello hello-world
```
Note
To see a full list of possible parameters for the Spring Boot CLI, run:
```
spring init --list
```

Navigate into the project directory. This example creates an endpoint to return “Hello world” in a Spring application. Add two additional imports and a new class for this mapping.

File: ~/hello-world/src/main/java/com/example/helloworld/HelloApplication.java

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package com.example.helloworld;

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

@SpringBootApplication
public class HelloApplication {

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

@RestController
class Hello {

    @RequestMapping("/")
    String index() {
        return "Hello world";
    }
}

Build the application. This creates a new directory called build in the project.
```
./gradlew build
```
Run the application embedded with the Tomcat Server. The application will run on a Tomcat servlet on localhost:8080. Press Ctrl+C to stop.
```
java -jar build/libs/hello-world-0.0.1-SNAPSHOT.jar
```
The application can run in-place without building a jar file first.
```
gradle bootRun
```
Test that the application is running correctly on localhost:
```
curl localhost:8080
```
```
Hello world
```
Stop the Tomcat server with CTRL+C.

Create an Init Script

Set the Spring Boot application as a service to start on reboot:

File: /etc/systemd/system/helloworld.service

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[Unit]
Description=Spring Boot HelloWorld
After=syslog.target
After=network.target[Service]
User=username
Type=simple

[Service]
ExecStart=/usr/bin/java -jar /home/linode/hello-world/build/libs/hello-world-0.0.1-SNAPSHOT.jar
Restart=always
StandardOutput=syslog
StandardError=syslog
SyslogIdentifier=helloworld

[Install]
WantedBy=multi-user.target

Start the service:
```
sudo systemctl start helloworld
```
Check the status is active:
```
sudo systemctl status helloworld
```

Reverse Proxy

Now that the Spring application is running as a service, an NGINX proxy allows opening the application to an unprivileged port and setting up SSL.

Create an NGINX configuration for the reverse proxy:

File: /etc/nginx/conf.d/helloworld.conf

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server {
        listen 80;
        listen [::]:80;

        server_name example.com;

        location / {
             proxy_pass http://localhost:8080/;
             proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
             proxy_set_header X-Forwarded-Proto $scheme;
             proxy_set_header X-Forwarded-Port $server_port;
        }
}

Test the configuration to make sure there are no errors:
```
sudo nginx -t
```
If there are no errors, restart NGINX so the changes take effect:
```
sudo systemctl restart nginx
```
The application is now accessible through the browser. Navigate to the public IP address of the Linode and the “Hello world” message should appear.

More Information

You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.

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