Step 3: Push the image to DockerHub<\/h3> Before pushing the image to the DockerHub repository, you have to tag the image that you want to push, use the below to tag the image<\/p>
docker tag kube-petclinic-app:3.0.0 techiescamp\/kube-petclinic-app:3.0.0<\/code><\/pre>In this command kube-petclinic-app:3.0.0<\/strong> is the name of the image I build and techiescamp\/kube-petclinic-app:3.0.0<\/strong> is my DockerHub repository and image tag.<\/p>Now, push the image to DockerHub using the command. Before proceeding, ensure you have logged in to docker hub<\/strong> from the CLI.<\/p>docker push techiescamp\/kube-petclinic-app:3.0.0<\/code><\/pre>Check if your image is pushed into DockerHub as shown below<\/p>Deploy Java & MySQL On Kubernetes<\/h2> Clone the Git repository given below which contains all the YAML manifest we used in this guide under 03-java-app-deployment<\/strong> folder.<\/p>git clone https:\/\/github.com\/techiescamp\/kubernetes-projects.git<\/code><\/pre>In the 03-java-app-deployment<\/strong> folder, you can see the YAML manifests in the below structure.<\/p>.\n\u251c\u2500\u2500 java-app\n\u2502 \u251c\u2500\u2500 configmap.yml\n\u2502 \u251c\u2500\u2500 hpa.yml\n\u2502 \u2514\u2500\u2500 java.yml\n\u251c\u2500\u2500 mysql\n\u2502 \u251c\u2500\u2500 configmap.yml\n\u2502 \u2514\u2500\u2500 mysql.yml\n\u2514\u2500\u2500 secret.yml<\/code><\/pre>Given below are the steps to deploy Java and MySQL on Kubernetes<\/p>
Step 1: Create Namespaces<\/h3> We are going to deploy the app and MySQL on two different namespaces so create two new namespaces pet-clinic-app<\/strong> and pet-clinic-db<\/strong>.<\/p>Run the following commands to create both namespace<\/p>
kubectl create ns pet-clinic-app\n\nkubectl create ns pet-clinic-db<\/code><\/pre>Step 2: Create Secrets<\/h3> CD into the 03-java-app-deployment <\/strong>directory and run the secret.yml<\/strong> in both pet-clinic-app<\/strong> and pet-clinic-db<\/strong> namespaces because the secret contains the MySQL login credentials which are needed in both MySQL and app deployment process.<\/p>apiVersion: v1\nkind: Secret\nmetadata:\n name: mysql-cred\n namespace: pet-clinic-app\ntype: Opaque\ndata:\n username: Y3J1bmNob3Bz\n password: Y3J1bmNob3BzQDEyMzQ=<\/code><\/pre>Just change the namespace and run the secret.yml<\/strong> file two times to create a secret in both pet-clinic-app<\/strong> and pet-clinic-db<\/strong> namespaces.<\/p>data:\n username: Y3J1bmNob3Bz\n password: Y3J1bmNob3BzQDEyMzQ=<\/code><\/pre>You can see the data in the above block is given in base64-encoded values because the secret won’t be created unless you specify your username and password in base64-encoded<\/strong> values.<\/p>You can use the echo<\/strong> command with base64<\/strong> to encode your data, the echo command will give the encoded values of your data. The command to encode your data is given below<\/p>echo -n '<data>' | base64<\/code><\/pre>For example, I set my username<\/strong> as crunchops<\/strong>, then the echo command will be<\/p>echo -n 'crunchops' | base64<\/code><\/pre>This command will give the encoded values of my data.<\/p>Now, create the secret in both namespaces using the following command.<\/p>
kubectl apply -f secret<\/code><\/pre>Run the following command to verify the secret is created in both namespace<\/p>
kubectl get secret -n pet-clinic-app\n\nkubectl get secret -n pet-clinic-db<\/code><\/pre>You will get the following output<\/p>Step 3: Create ConfigMap for MySQL<\/h3> CD into the 03-java-app-deployment\/mysql <\/strong>directory and run the configmap.yml<\/strong>.<\/p>apiVersion: v1\nkind: ConfigMap\nmetadata:\n name: mysql-configmap\n namespace: pet-clinic-db\ndata:\n init.sql: |\n CREATE USER '$MYSQL_USER'@'%' IDENTIFIED BY '$MYSQL_PASSWORD';\n GRANT ALL PRIVILEGES ON petclinic.* TO '$MYSQL_USER'@'%';\n FLUSH PRIVILEGES;\n\n USE petclinic;\n\n CREATE TABLE IF NOT EXISTS vets (\n id INT(4) UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,\n first_name VARCHAR(30),\n last_name VARCHAR(30),\n INDEX(last_name)\n ) engine=InnoDB;\n\n....... View Complete File content on the mysql\/configmap.yml file ......<\/code><\/pre>This creates a configmap mysql-configmap<\/strong> on the pet-clinic-db<\/strong> namespace, that contains the SQL command to create a user, password, and tables on the database, and to insert data on the table.<\/p>It gets the username and password from env variables, which are retrieved from the secret.<\/p>
Run the below command to create a configmap.<\/p>
kubectl apply -f configmap.yml<\/code><\/pre>Now, run the following command to verify if the ConfigMap is created<\/p>
kubectl get cm -n pet-clinic-db<\/code><\/pre>You will get the following output<\/p>Step 4: Deploy MySQL Database<\/h3> CD into the 03-java-app-deployment\/mysql <\/strong>directory and run the mysql.yml<\/strong>.<\/p>apiVersion: apps\/v1\nkind: StatefulSet\nmetadata:\n name: mysql\n namespace: pet-clinic-db\nspec:\n serviceName: \"mysql\"\n replicas: 1\n selector:\n matchLabels:\n app: mysql\n template:\n metadata:\n labels:\n app: mysql\n spec:\n containers:\n - name: mysql\n image: mysql:latest\n env:\n - name: MYSQL_RANDOM_ROOT_PASSWORD\n value: \"yes\"\n - name: MYSQL_USER\n valueFrom:\n secretKeyRef:\n name: mysql-cred\n key: username\n - name: MYSQL_PASSWORD\n valueFrom:\n secretKeyRef:\n name: mysql-cred\n key: password\n - name: MYSQL_DATABASE\n value: petclinic\n volumeMounts:\n - name: mysql-config\n mountPath: \/docker-entrypoint-initdb.d\n resources:\n requests:\n memory: \"256Mi\"\n cpu: \"100m\"\n limits:\n memory: \"512Mi\"\n cpu: \"200m\"\n volumes:\n - name: mysql-config\n configMap:\n name: mysql-configmap\n---\napiVersion: v1\nkind: Service\nmetadata:\n name: mysql-service\n namespace: pet-clinic-db\nspec:\n type: NodePort\n selector:\n app: mysql\n ports:\n - protocol: TCP\n port: 3306\n targetPort: 3306\n nodePort: 30244<\/code><\/pre>This file deploys a MySQL<\/strong> statefulset database on the pet-clinic-db<\/strong> namespace and also a nodeport service mysql-service<\/strong> on the pet-clinic-db<\/strong> namespace so we can log in to MySQL from outside the cluster.<\/p>It gets the database username and password from the secret you created before.<\/p>
The docker-entrypoint-initdb.d<\/code><\/strong> directory is part of the MySQL image. Any MySQL scripts placed in this folder will be executed during MySQL startup. It is primarily used for running database initialization scripts.<\/p>In our setup, we placed an init script (init.sql<\/code><\/strong>) in this folder through a ConfigMap (mysql-configmap<\/strong>). init.sql <\/code><\/strong>creates the username, password, and tables for our application. The script retrieves the username and password from environment variables set by the secret object using secretKeyRef<\/code><\/strong><\/p>Run the below command to deploy the MySQL database.<\/p>
kubectl apply -f mysql.yml<\/code><\/pre>Now, run the following command to check if the MySQL StatefulSet has been created.<\/p>
kubectl get sts -n pet-clinic-db<\/code><\/pre>You will get the following output<\/p>Step 5: Create ConfigMap for Java Application<\/h3> CD into the 03-java-app-deployment\/java-app<\/strong> folder and run the configmap.yml<\/strong>.<\/p>apiVersion: v1\nkind: ConfigMap\nmetadata:\n name: java-app-config\n namespace: pet-clinic-app\ndata:\n application.properties: |\n # database init, supports mysql too\n database=mysql\n spring.datasource.url=jdbc:mysql:\/\/mysql-service.pet-clinic-db.svc.cluster.local:3306\/petclinic\n spring.datasource.username=${DB_USERNAME}\n spring.datasource.password=${DB_PASSWORD}\n # SQL is written to be idempotent so this is safe\n spring.sql.init.mode=always\n\n # Web\n spring.thymeleaf.mode=HTML\n\n # JPA\n spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQLDialect\n spring.jpa.open-in-view=true\n\n # Internationalization\n spring.messages.basename=messages\/messages\n\n # Actuator\n management.endpoints.web.exposure.include=*\n # Logging\n #logging.config=classpath:logback-spring.xml\n logging.level.org.springframework=INFO\n # logging.level.org.springframework.web=DEBUG\n # logging.level.org.springframework.context.annotation=TRACE\n\n # Maximum time static resources should be cached\n spring.web.resources.cache.cachecontrol.max-age=12h<\/code><\/pre>Run the below command to create a configmap.<\/p>
kubectl apply -f configmap.yml<\/code><\/pre>This creates a configmap java-app-config<\/strong> on the pet-clinic-app<\/strong> namespace, which contains content of the application.properties file which helps the application to connect with the MySQL database.<\/p>The username and password are given as a variable so that it can get the username and password from the env variables, which are retrieved from the secret.<\/p>
Run the following command to check if the configmap is created<\/p>
kubectl get cm -n pet-clinic-app<\/code><\/pre>You will get the following output<\/p>Step 6: Deploy Java Application<\/h3>apiVersion: apps\/v1\nkind: Deployment\nmetadata:\n name: java-app\n namespace: pet-clinic-app\nspec:\n replicas: 1\n selector:\n matchLabels:\n app: java-app\n template:\n metadata:\n labels:\n app: java-app\n spec:\n containers:\n - name: java-app-container\n image: techiescamp\/kube-petclinic-app:3.0.0\n env:\n - name: DB_USERNAME\n valueFrom:\n secretKeyRef:\n name: mysql-cred\n key: username\n - name: DB_PASSWORD\n valueFrom:\n secretKeyRef:\n name: mysql-cred\n key: password\n resources:\n requests:\n memory: \"256Mi\"\n cpu: \"100m\"\n limits:\n memory: \"512Mi\"\n cpu: \"200m\"\n ports:\n - containerPort: 8080\n volumeMounts:\n - name: java-app-config\n mountPath: \"\/opt\/config\"\n command: [\"java\", \"-jar\", \"\/app\/java.jar\", \"--spring.config.location=\/opt\/config\/application.properties\", \"--spring.profiles.active=mysql\"]\n startupProbe:\n httpGet:\n path: \/actuator\/health\n port: 8080\n failureThreshold: 30\n periodSeconds: 20\n initialDelaySeconds: 180\n readinessProbe:\n httpGet:\n path: \/actuator\/health\/readiness\n port: 8080\n periodSeconds: 10\n failureThreshold: 3\n timeoutSeconds: 10\n livenessProbe:\n httpGet:\n path: \/actuator\/health\/liveness\n port: 8080\n periodSeconds: 15\n failureThreshold: 3\n timeoutSeconds: 10\n volumes:\n - name: java-app-config\n configMap:\n name: java-app-config\n\n---\napiVersion: v1\nkind: Service\nmetadata:\n name: java-app-service\n namespace: pet-clinic-app\nspec:\n selector:\n app: java-app\n type: NodePort\n ports:\n - protocol: TCP\n port: 8080\n targetPort: 8080\n nodePort: 32000<\/code><\/pre>This file deploys the Java application java-app<\/strong> on the pet-clinic-app<\/strong> namespace and also a nodeport service java-app-service<\/strong> on the pet-clinic-app<\/strong> namespace so we can access the application on the web browser.<\/p>It gets the database username and password from the secret you created before and the application.properties<\/strong> file gets the username and password from the env<\/strong> during startup.<\/p>The command is used to run the application JAR<\/strong> file along with the application.properties<\/strong> file so that the application can access the MySQL database.<\/p>Also, I have added health checks for this application:<\/p>\n\n
\nstartupProbe<\/strong> – This keeps the readinessProbe and livenessProbe on hold until the application is started and configured to check the path \/actuator\/health<\/strong>.<\/li>\n\n\nreadinessProbe<\/strong> – This checks if the application is ready to accept traffic using the readiness path \/actuator\/health\/readiness<\/strong>. If this probe fails, it won’t receive any traffic.<\/li>\n\n\nlivenessProbe<\/strong> – Checks if the application is up and running using the liveness path \/actuator\/health\/liveness<\/strong>. If the probe fails, Kubernetes will restart the po<\/span>d.<\/li>\n<\/ol>\n\nRun the below command to deploy the Java application.<\/p>
kubectl apply -f java.yml<\/code><\/pre>After deploying the application, run the following command to check if the deployment pods are up and running. It takes minimum 2min for the pods to get ready.<\/p>
kubectl get deploy -n pet-clinic-app<\/code><\/pre>You will get the following output.<\/p>Step 7: Deploy HorizontalPodAutoscaler (HPA)<\/h3> For HPA to work, you need to have a metrics server running in the cluster.<\/p>
If you don’t have a metrics server, you can install the Metrics server<\/strong> using the following command.<\/p>kubectl apply -f https:\/\/raw.githubusercontent.com\/techiescamp\/kubeadm-scripts\/main\/manifests\/metrics-server.yaml<\/code><\/pre>Now, run the top command to check if the metrics server is installed properly<\/p>
kubectl top po -n pet-clinic-app<\/code><\/pre>You will get the following output.<\/p>Now, deploy the HorizontalPodAutoscaler<\/code><\/strong> in your cluster.<\/p>You can find the below HPA<\/strong> file inside the 03-java-app-deployment\/java-app<\/strong> directory.<\/p>apiVersion: autoscaling\/v2\nkind: HorizontalPodAutoscaler\nmetadata:\n name: java-app-hpa\n namespace: pet-clinic-app\nspec:\n scaleTargetRef:\n apiVersion: apps\/v1\n kind: Deployment\n name: java-app\n minReplicas: 1\n maxReplicas: 3\n metrics:\n - type: Resource\n resource:\n name: cpu\n target:\n type: Utilization\n averageUtilization: 50<\/code><\/pre>This will deploy the HPA in the pet-clinic-app namespace.<\/p>
It is configured to scale the target deployment Java app<\/strong> if the pod’s CPU utilization is 50% and its maximum replica count is 3.<\/p>Run the following command to deploy HPA<\/p>
kubectl apply -f hpa.yml<\/code><\/pre>Now, run the following command to check if the HPA is deployed<\/p>
kubectl get hpa -n pet-clinic-app<\/code><\/pre>You will get the following output<\/p>You can see the CPU usage of the target deployment and the number of pods available.<\/p>
Step 8: Access the Java Application<\/h3> Once the pod is up and running, check if the application is deployed properly by trying to access it on the browser, search on the browser as {node-IP:nodeport}<\/code><\/strong> you will get the following<\/p>Step 9: Clean Up<\/h3> It’s important to clean up the setup if it’s no longer needed; run the following commands to clean up the setup.<\/p>
1. Delete Java App Deployment<\/strong><\/p>Let’s start with deleting the Java application, CD into the 03-java-app-deployment\/java-app<\/strong> folder and run the following command<\/p>kubectl delete -f .<\/code><\/pre>This command will delete all the resources created by the manifest files inside the java-app directory, it deletes the Java app deployment, configmap, and HPA.<\/p>
2. Delete MySQL<\/strong><\/p>The next step is to delete MySQL, CD into the 03-java-app-deployment\/mysql<\/strong> folder and run the following command<\/p>kubectl delete -f .<\/code><\/pre>This command will delete all the resources created by the manifest files inside the mysql directory, it deletes the MySQL statefulset and configmap.<\/p>
3. Delete Secret<\/strong><\/p>To delete the secret in both namespace, CD into the 03-java-app-deployment<\/strong> and run the following commands<\/p>Just change the namespace in the secret.yml<\/strong> file to pet-clinic-app<\/strong> and pet-clinic-db<\/strong> then run the following command twice, once for each namespace.<\/p>kubectl delete -f secret.yml<\/code><\/pre>4. Delete Namespaces<\/strong><\/p>Finally, delete the namespaces, run the following command to delete both namespaces<\/p>
kubectl delete ns pet-clinic-app\n\nkubectl delete ns pet-clinic-db<\/code><\/pre>Conclusion<\/h2> In summary, we have built the pet clinic Java application using maven, pushed it to the docker hub, used the image to deploy the application on Kubernetes, and configured a MySQL database to it.<\/p>
I believe you find this blog helpful in understanding deploying applications and configuring the database to the application on Kubernetes.<\/p>\n
Ngu\u1ed3n:<\/strong> How to Deploy Java App With MySQL on Kubernetes \u2014 DevOpsCube<\/a><\/p>","protected":false},"excerpt":{"rendered":"Source: https:\/\/devopscube.com\/deploy-java-app-kubernetes\/<\/p>\n","protected":false},"author":1,"featured_media":1006,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1005","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-devops"],"_links":{"self":[{"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=\/wp\/v2\/posts\/1005","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1005"}],"version-history":[{"count":0,"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=\/wp\/v2\/posts\/1005\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=\/wp\/v2\/media\/1006"}],"wp:attachment":[{"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1005"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1005"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.ngocha.biz\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1005"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\"Java](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/java-applicationmysql-1.gif\")
<\/figure>![\"Jar](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-149-4.png\")
<\/figure>![\"Checking](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-258-1.png\")
<\/figure>![\"Viewing](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-257-1.png\")
<\/figure>![\"Encoding](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-269.png\")
<\/figure>![\"verifying](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-259.png\")
<\/figure>![\"verifying](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-262-1.png\")
<\/figure>![\"verifying](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-263-1.png\")
<\/figure>![\"verifying](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-264-1.png\")
<\/figure>![\"verifying](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-265-1.png\")
<\/figure>![\"verifying](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-266-1.png\")
<\/figure>![\"verifying](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-267-1.png\")
<\/figure>![\"\"](\"https:\/\/storage.ghost.io\/c\/5f\/2f\/5f2f4d20-2abf-4534-8d40-7aa233aedd43\/content\/images\/2025\/03\/image-49-7.png\")
<\/figure>