fix

Dockerfile

@@ -0,0 +1,8 @@
+FROM openjdk:8-jre-alpine
+
+EXPOSE 8080
+
+COPY ./target/java-maven-app-1.0-SNAPSHOT.jar /usr/app/
+WORKDIR /usr/app
+
+ENTRYPOINT ["java", "-jar", "java-maven-app-1.0-SNAPSHOT.jar"]

Jenkinsfile

@@ -1,3 +1,13 @@
+#!/usr/bin/env groovy
+
+library identifier: 'jenkins-shared-library@master', retriever: modernSCM(
+        [$class: 'GitSCMSource',
+         remote: 'https://gitlab.com/nanuchi/jenkins-shared-library.git',
+         credentialsId: 'gitlab-credentials'
+        ]
+)
+
+
 def gv
 
 pipeline {
@@ -16,14 +26,16 @@ pipeline {
         stage("build jar") {
             steps {
                 script {
-                    gv.buildJar()
+                    buildJar()
                 }
             }
         }
-        stage("build image") {
+        stage("build and push image") {
             steps {
                 script {
-                    gv.buildImage()
+                    buildImage 'nanajanashia/demo-app:jma-3.0'
+                    dockerLogin()
+                    dockerPush 'nanajanashia/demo-app:jma-3.0'
                 }
             }
         }

script.groovy

@@ -1,17 +1,3 @@
-def buildJar() {
-    echo "building the application..."
-    sh 'mvn package'
-} 
-
-def buildImage() {
-    echo "building the docker image..."
-    withCredentials([usernamePassword(credentialsId: 'docker-hub-repo', passwordVariable: 'PASS', usernameVariable: 'USER')]) {
-        sh 'docker build -t nanajanashia/demo-app:jma-2.0 .'
-        sh "echo $PASS | docker login -u $USER --password-stdin"
-        sh 'docker push nanajanashia/demo-app:jma-2.0'
-    }
-} 
-
 def deployApp() {
     echo 'deploying the application...'
 }