Continuing this short series of writing a simple echo service web API along with the docker and k8s requirements, we\u2019re now going to turn our attention to a Java implementation.<\/p>\n
Implementation<\/strong><\/p>\n I’m going to be using JetBrains IntelliJ. <\/p>\n We’re setting the PORT here from the environment variable as this will be supplied via the Dockerfile\n<\/li>\n Dockerfile<\/strong><\/p>\n Next up we need to create our Dockerfile<\/p>\n Note: In Linux port 80 might be locked down, hence we use port 8080 – to override the default port in phx we also set the environment variable PORT.<\/p>\n To build this, run<\/p>\n Don\u2019t forget to change the name to your preferred name.<\/p>\n To test this, run<\/p>\n Kubernetes<\/strong><\/p>\n If all wen well we’ve not tested our application and see it working from a docker image, so now we need to create the deployment etc. for Kubernete’s. Let’s assume you’ve pushed you image to Docker or another container registry such as Azure – I’m call my container registry putridparrotreg<\/em>.<\/p>\n I’m also not going to use helm at this point as I just want a (relatively) simple yaml file to run from kubectl, so create a deployment.yaml file, we’ll store all the configurations, deployment, service and ingress in this one file jus for simplicity.<\/p>\n\n
\r\n<dependencies>\r\n <dependency>\r\n <groupId>org.springframework.boot<\/groupId>\r\n <artifactId>spring-boot-starter-web<\/artifactId>\r\n <version>3.5.5<\/version>\r\n <\/dependency>\r\n<\/dependencies>\r\n<\/pre>\n<\/li>\n
\r\n<build>\r\n <plugins>\r\n <plugin>\r\n <groupId>org.springframework.boot<\/groupId>\r\n <artifactId>spring-boot-maven-plugin<\/artifactId>\r\n <version>3.5.5<\/version>\r\n <executions>\r\n <execution>\r\n <goals>\r\n <goal>repackage<\/goal>\r\n <\/goals>\r\n <\/execution>\r\n <\/executions>\r\n <\/plugin>\r\n <\/plugins>\r\n<\/build>\r\n<\/pre>\n<\/li>\n
\r\npackage com.putridparrot;\r\n\r\nimport org.springframework.boot.SpringApplication;\r\nimport org.springframework.boot.autoconfigure.SpringBootApplication;\r\n\r\nimport java.util.HashMap;\r\nimport java.util.Map;\r\n\r\n@SpringBootApplication\r\npublic class EchoServiceApplication {\r\n public static void main(String[] args) {\r\n SpringApplication app = new SpringApplication(EchoServiceApplication.class);\r\n Map<String, Object> props = new HashMap<>();\r\n props.put("server.port", System.getenv("PORT"));\r\n app.setDefaultProperties(props);\r\n app.run(args);\r\n }\r\n}\r\n<\/pre>\n\r\npackage com.putridparrot;\r\n\r\nimport org.springframework.web.bind.annotation.*;\r\n\r\n@RestController\r\npublic class EchoController {\r\n\r\n @GetMapping("\/echo")\r\n public String echo(@RequestParam(name = "text", defaultValue = "") String text) {\r\n return String.format("Java Echo: %s", text);\r\n }\r\n\r\n @GetMapping("\/readyz")\r\n public String readyz() {\r\n return "OK";\r\n }\r\n\r\n @GetMapping("\/livez")\r\n public String livez() {\r\n return "OK";\r\n }\r\n}\r\n<\/pre>\n<\/li>\n<\/ul>\n\r\nFROM maven:3.9.11-eclipse-temurin-21 AS builder\r\n\r\nWORKDIR \/app\r\n\r\nCOPY . .\r\nRUN mvn clean package -DskipTests\r\n\r\nFROM eclipse-temurin:21-jre AS runtime\r\n\r\nWORKDIR \/app\r\n\r\nCOPY --from=builder \/app\/target\/echo_service-1.0-SNAPSHOT.jar .\/echo-service.jar\r\n\r\nENV PORT=8080\r\nEXPOSE 8080\r\n\r\nENTRYPOINT ["java", "-jar", "echo-service.jar"]\r\n<\/pre>\n
\r\ndocker build -t putridparrot.echo_service:v1 .\r\n<\/pre>\n
\r\ndocker run -p 8080:8080 putridparrot.echo_service:v1\r\n<\/pre>\n
\r\napiVersion: apps\/v1\r\nkind: Deployment\r\nmetadata:\r\n name: echo\r\n namespace: dev\r\n labels:\r\n app: echo\r\nspec:\r\n replicas: 1\r\n selector:\r\n matchLabels:\r\n app: echo\r\n template:\r\n metadata:\r\n labels:\r\n app: echo\r\n spec:\r\n containers:\r\n - name: echo\r\n image: putridparrotreg\/putridparrot.echo_service:v1\r\n ports:\r\n - containerPort: 8080\r\n resources:\r\n requests:\r\n memory: "100Mi"\r\n cpu: "100m"\r\n limits:\r\n memory: "200Mi"\r\n cpu: "200m"\r\n livenessProbe:\r\n httpGet:\r\n path: \/livez\r\n port: 8080\r\n initialDelaySeconds: 30\r\n periodSeconds: 10\r\n readinessProbe:\r\n httpGet:\r\n path: \/readyz\r\n port: 8080\r\n initialDelaySeconds: 5\r\n periodSeconds: 5\r\n\r\n---\r\napiVersion: v1\r\nkind: Service\r\nmetadata:\r\n name: echo_service\r\n namespace: dev\r\n labels:\r\n app: echo\r\nspec:\r\n type: ClusterIP\r\n selector:\r\n app: echo \r\n ports:\r\n - name: http\r\n port: 80\r\n targetPort: 8080\r\n protocol: TCP\r\n---\r\napiVersion: networking.k8s.io\/v1\r\nkind: Ingress\r\nmetadata:\r\n name: echo-ingress\r\n namespace: dev\r\n annotations:\r\n kubernetes.io\/ingress.class: "nginx"\r\n nginx.ingress.kubernetes.io\/rewrite-target: \/\r\nspec:\r\n rules:\r\n - host: mydomain.com\r\n http:\r\n paths:\r\n - path: \/\r\n pathType: Prefix\r\n backend:\r\n service:\r\n name: echo_service\r\n port:\r\n number: 80\r\n<\/pre>\n