Chapter 4. Developing and deploying a Spring Boot runtime application
In addition to using an example, you can create new Spring Boot applications from scratch and deploy them to OpenShift.
The recommended approach for specifying and using supported and tested Maven artifacts in a Spring Boot application is to use the OpenShift Application Runtimes Spring Boot BOM.
4.1. Developing Spring Boot application
For a basic Spring Boot application, you need to create the following:
- A Java class containing Spring Boot methods.
-
A
pom.xml
file containing information required by Maven to build the application.
The following procedure creates a simple Greeting
application that returns "{"content":"Greetings!"}" as response.
For building and deploying your applications to OpenShift, Spring Boot 2.2 only supports builder images based on OpenJDK 8 and OpenJDK 11. Oracle JDK and OpenJDK 9 builder images are not supported.
Prerequisites
- OpenJDK 8 or OpenJDK 11 installed.
- Maven installed.
Procedure
Create a new directory
myApp
, and navigate to it.$ mkdir myApp $ cd myApp
This is the root directory for the application.
Create directory structure
src/main/java/com/example/
in the root directory, and navigate to it.$ mkdir -p src/main/java/com/example/ $ cd src/main/java/com/example/
Create a Java class file
MyApp.java
containing the application code.package com.example; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.ResponseBody; import org.springframework.web.bind.annotation.RestController; @SpringBootApplication @RestController public class MyApp { public static void main(String[] args) { SpringApplication.run(MyApp.class, args); } @RequestMapping("/") @ResponseBody public Message displayMessage() { return new Message(); } static class Message { private String content = "Greetings!"; public String getContent() { return content; } public void setContent(String content) { this.content = content; } } }
Create a
pom.xml
file in the application root directorymyApp
with the following content:<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId> <artifactId>my-app</artifactId> <version>1.0.0-SNAPSHOT</version> <name>MyApp</name> <description>My Application</description> <!-- Specify the JDK builder image used to build your application. --> <!-- Use OpenJDK 8 and OpenJDK 11-based images. OracleJDK-based images are not supported. --> <properties> <fabric8.generator.from>registry.access.redhat.com/redhat-openjdk-18/openjdk18-openshift:latest</fabric8.generator.from> </properties> <!-- Import dependencies from the Spring Boot BOM. --> <dependencyManagement> <dependencies> <dependency> <groupId>dev.snowdrop</groupId> <artifactId>snowdrop-dependencies</artifactId> <version>2.2.11.SP1-redhat-00001</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-tomcat</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-actuator</artifactId> </dependency> <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> <version>2.2.11.RELEASE</version> </plugin> </plugins> </build> <!-- Specify the repositories containing Spring Boot artifacts --> <repositories> <repository> <id>redhat-ga</id> <name>Red Hat GA Repository</name> <url>https://maven.repository.redhat.com/ga/</url> </repository> </repositories> <pluginRepositories> <pluginRepository> <id>redhat-ga</id> <name>Red Hat GA Repository</name> <url>https://maven.repository.redhat.com/ga/</url> </pluginRepository> </pluginRepositories> </project>
Build the application using Maven from the root directory of the application.
$ mvn spring-boot:run
Verify that the application is running.
Using
curl
or your browser, verify your application is running athttp://localhost:8080
.$ curl http://localhost:8080 {"content":"Greetings!"}
Additional information
- As a recommended practice, you can configure liveness and readiness probes to enable health monitoring for your application when running on OpenShift. To learn how application health monitoring on OpenShift works, try the Health Check example.
4.2. Deploying Spring Boot application to OpenShift
To deploy your Spring Boot application to OpenShift, configure the pom.xml
file in your application and then use the Fabric8 Maven plugin. You can specify a Java image by replacing the fabric8.generator.from
URL in the pom.xml
file.
The images are available in the Red Hat Ecosystem Catalog.
<fabric8.generator.from>IMAGE_NAME</fabric8.generator.from>
For example, the Java image for RHEL 7 with OpenJDK 8 is specified as:
<fabric8.generator.from>registry.access.redhat.com/redhat-openjdk-18/openjdk18-openshift:latest</fabric8.generator.from>
4.2.1. Supported Java images for Spring Boot
Spring Boot is certified and tested with various Java images that are available for different operating systems. For example, Java images are available for RHEL 7 with OpenJDK 8 or OpenJDK 11.
Spring Boot introduces support for building and deploying Spring Boot applications to OpenShift with OCI-compliant Universal Base Images for Red Hat OpenJDK 8 and Red Hat OpenJDK 11 on RHEL 8.
Similar images are available on IBM Z.
You require Docker or podman authentication to access the RHEL 8 images in the Red Hat Ecosystem Catalog.
The following table lists the images supported by Spring Boot for different architectures. It also provides links to the images available in the Red Hat Ecosystem Catalog. The image pages contain authentication procedures required to access the RHEL 8 images.
4.2.1.1. Images on x86_64 architecture
OS | Java | Red Hat Ecosystem Catalog |
---|---|---|
RHEL 7 | OpenJDK 8 | |
RHEL 7 | OpenJDK 11 | |
RHEL 8 | OpenJDK 8 | |
RHEL 8 | OpenJDK 11 |
The use of a RHEL 8-based container on a RHEL 7 host, for example with OpenShift 3 or OpenShift 4, has limited support. For more information, see the Red Hat Enterprise Linux Container Compatibility Matrix.
4.2.1.2. Images on s390x (IBM Z) architecture
OS | Java | Red Hat Ecosystem Catalog |
---|---|---|
RHEL 8 | Eclipse OpenJ9 11 |
The use of a RHEL 8-based container on a RHEL 7 host, for example with OpenShift 3 or OpenShift 4, has limited support. For more information, see the Red Hat Enterprise Linux Container Compatibility Matrix.
4.2.2. Preparing Spring Boot application for OpenShift deployment
For deploying your Spring Boot application to OpenShift, it must contain:
-
Launcher profile information in the application’s
pom.xml
file.
In the following procedure, a profile with Fabric8 Maven plugin is used for building and deploying the application to OpenShift.
Prerequisites
- Maven is installed.
- Docker or podman authentication into Red Hat Ecosystem Catalog to access RHEL 8 images.
Procedure
Add the following content to the
pom.xml
file in the application root directory:... <profiles> <profile> <id>openshift</id> <build> <plugins> <plugin> <groupId>io.fabric8</groupId> <artifactId>fabric8-maven-plugin</artifactId> <version>4.4.1</version> <executions> <execution> <goals> <goal>resource</goal> <goal>build</goal> </goals> </execution> </executions> </plugin> </plugins> </build> </profile> </profiles>
Replace the
fabric8.generator.from
property in thepom.xml
file to specify the OpenJDK image that you want to use.x86_64 architecture
RHEL 7 with OpenJDK 8
<fabric8.generator.from>registry.access.redhat.com/redhat-openjdk-18/openjdk18-openshift:latest</fabric8.generator.from>
RHEL 7 with OpenJDK 11
<fabric8.generator.from>registry.access.redhat.com/openjdk/openjdk-11-rhel7:latest</fabric8.generator.from>
RHEL 8 with OpenJDK 8
<fabric8.generator.from>registry.access.redhat.com/ubi8/openjdk-8:latest</fabric8.generator.from>
RHEL 8 with OpenJDK 11
<fabric8.generator.from>registry.access.redhat.com/ubi8/openjdk-11:latest</fabric8.generator.from>
s390x (IBM Z) architecture
RHEL 8 with Eclipse OpenJ9 11
<fabric8.generator.from>registry.access.redhat.com/openj9/openj9-11-rhel8:latest</fabric8.generator.from>
4.2.3. Deploying Spring Boot application to OpenShift using Fabric8 Maven plugin
To deploy your Spring Boot application to OpenShift, you must perform the following:
- Log in to your OpenShift instance.
- Deploy the application to the OpenShift instance.
Prerequisites
-
oc
CLI client installed. - Maven installed.
Procedure
Log in to your OpenShift instance with the
oc
client.$ oc login ...
Create a new project in the OpenShift instance.
$ oc new-project MY_PROJECT_NAME
Deploy the application to OpenShift using Maven from the application’s root directory. The root directory of an application contains the
pom.xml
file.$ mvn clean fabric8:deploy -Popenshift
This command uses the Fabric8 Maven Plugin to launch the S2I process on OpenShift and start the pod.
Verify the deployment.
Check the status of your application and ensure your pod is running.
$ oc get pods -w NAME READY STATUS RESTARTS AGE MY_APP_NAME-1-aaaaa 1/1 Running 0 58s MY_APP_NAME-s2i-1-build 0/1 Completed 0 2m
The
MY_APP_NAME-1-aaaaa
pod should have a status ofRunning
once it is fully deployed and started.Your specific pod name will vary.
Determine the route for the pod.
Example Route Information
$ oc get routes NAME HOST/PORT PATH SERVICES PORT TERMINATION MY_APP_NAME MY_APP_NAME-MY_PROJECT_NAME.OPENSHIFT_HOSTNAME MY_APP_NAME 8080
The route information of a pod gives you the base URL which you use to access it.
In this example,
http://MY_APP_NAME-MY_PROJECT_NAME.OPENSHIFT_HOSTNAME
is the base URL to access the application.Verify that your application is running in OpenShift.
$ curl http://MY_APP_NAME-MY_PROJECT_NAME.OPENSHIFT_HOSTNAME {"content":"Greetings!"}
4.3. Deploying Spring Boot application to stand-alone Red Hat Enterprise Linux
To deploy your Spring Boot application to stand-alone Red Hat Enterprise Linux, configure the pom.xml
file in the application, package it using Maven and deploy using the java -jar
command.
Prerequisites
- RHEL 7 or RHEL 8 installed.
4.3.1. Preparing Spring Boot application for stand-alone Red Hat Enterprise Linux deployment
For deploying your Spring Boot application to stand-alone Red Hat Enterprise Linux, you must first package the application using Maven.
Prerequisites
- Maven installed.
Procedure
Add the following content to the
pom.xml
file in the application’s root directory:... <!-- Specify target artifact type for the repackage goal. --> <packaging>jar</packaging> ... <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <version>${spring-boot.version}</version> <executions> <execution> <goals> <goal>repackage</goal> </goals> </execution> </executions> </plugin> </plugins> </build> ...
Package your application using Maven.
$ mvn clean package
The resulting JAR file is in the
target
directory.
4.3.2. Deploying Spring Boot application to stand-alone Red Hat Enterprise Linux using jar
To deploy your Spring Boot application to stand-alone Red Hat Enterprise Linux, use java -jar
command.
Prerequisites
- RHEL 7 or RHEL 8 installed.
- OpenJDK 8 or OpenJDK 11 installed.
- A JAR file with the application.
Procedure
Deploy the JAR file with the application.
$ java -jar my-project-1.0.0.jar
Verify the deployment.
Use
curl
or your browser to verify your application is running athttp://localhost:8080
:$ curl http://localhost:8080