Example Spring Boot REST API

A very simple example project using Spring Boot to build a rest API. The example project is intended to showcase how you can build an application based upon the spring boot framework in combination with Maven. The example code is based upon the example from Spring which can be found at https://spring.io/guides/gs/rest-service/ . It is not the intention of the repository to provide you with a solution which can be used in a real-world solution. It is rather intended as an informational guideline on how to use Spring Boot and Maven to build a REST API.

prerequisites

Even though compiling and running the example included in the example will work on a large set of configurations we have used a specific set of components which did work. To ensure the same experience you can use the below prerequisites as guidance on preparing your environment

Select the operating system

In our case we used Oracle Linux 6 as an operating system. To be more precise we used Oracle Linux 6.9 as it is provided as a docker container by Oracle. You can find the docker container at https://github.com/oracle/ol-container-images/tree/master/6.9 and it is also located at https://hub.docker.com/_/oraclelinux/

to get the docker container we used you can use the below command:

docker pull oraclelinux:6.9

Install Java

We will need java, for this we use Java OpenJDK 1.8.0 which is available from the standard Oracle YUM server, this means we can install java with yum with the below command:

yum -y install java-1.8.0-openjdk-devel

you also will have to ensure you set JAVA_HOME. As this is a temporary environment we will just use export directly in our sessions and not set it in persistent manner (which you do want in other cases). To quickly set JAVA_HOME we used the below command:

export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.131-0.b11.el6_9.x86_64/

Install Maven

Maven will be requried for the build process. We base the installation of maven on the process described in this blogpost which outlines the installation of Maven: http://johanlouwers.blogspot.nl/2017/04/oracle-linux-install-maven-with-yum.html

The basic command needed are the two below. The first is to ensure that the yum repo file is present which will take care of ensuring that maven can be installed the second command will install maven itself.

wget http://repos.fedorapeople.org/repos/dchen/apache-maven/epel-apache-maven.repo -O /etc/yum.repos.d/epel-apache-maven.repo

yum install -y apache-maven

Running the example

The below steps will take you through downlaoding, packaging and running the example project. Following the steps (after you ensured you have the prerequisites in place) should be straight forward.

step 1 - getting the code

Getting the code on your machine can be done using the git command as shown in the example below. this will ensure you will get the source code including the pom.xml file which is needed by Maven to build the code into a package

git clone https://github.com/louwersj/example_springboot_RESTAPI

step 2 - compile and package the code

As soon as you have retrieved the code you will have to compile and package your code. The result of this will be a jar file which you can use to run the example project. Using maven you can package the appication with the command shown below:

mvn clean package

step 3 - running the code

In the previous step we packaged the code which resulted in a self sufficient .jar file able to run the application. You can use this .jar file to run the application on the machine you build the code or on a different machine. running it can be done by using the below java command to start it. This should start the embeded application server and run the code which makes it availabel on port 8080

java -jar gs-rest-service-0.1.0.jar

step 4 - testing the application

Now that we have the code running you can test if it serves you what is expected from it. The code is intended to provide you a JSON file as soon as you call /greeting on port 8080. This means that we can use curl on the commandline to do so.

curl http://localhost:8080/greeting

The above example test should give you something like the below response(which can differ on id as it is raise by one every time you call greeting

{"id":8,"content":"Hello, World!"}

Using it with Docker

you can include plugins to build a docker conatiner in your pom.xml file. When done correctly the result of a maven build could become a container in your registry. A detailed explanation of this principle is given on this site: https://springframework.guru/running-spring-boot-in-a-docker-container/