Java 8 to 11 Migration: Complete Migration with Documentation

Dockerfile

@@ -2,8 +2,8 @@
 # Stage 1
 #----------------------------------
 
-# Import docker image with maven installed
-FROM maven:3.8.3-openjdk-17 as builder 
+# Import docker image with maven installed (Java 11 for migration)
+FROM maven:3.8.8-eclipse-temurin-11 as builder
 
 # Add maintainer, so that new user will understand who had written this Dockerfile
 MAINTAINER Madhup Pandey<madhuppandey2908@gmail.com>
@@ -24,8 +24,8 @@ RUN mvn clean install -DskipTests=true
 # Stage 2
 #--------------------------------------
 
-# Import small size java image
-FROM openjdk:17-alpine as deployer
+# Import small size java image (Java 11 for migration)
+FROM eclipse-temurin:11-jre-alpine as deployer
 
 # Copy build from stage 1 (builder)
 COPY --from=builder /src/target/*.jar /src/target/bankapp.jar

Jenkinsfile

@@ -2,8 +2,15 @@
 pipeline {
     agent any
 
+    tools {
+        jdk 'JDK11'  // Configure JDK 11 in Jenkins Global Tool Configuration
+        maven 'Maven3'  // Ensure Maven 3.x is configured
+    }
+
     environment{
         SONAR_HOME = tool "Sonar"
+        JAVA_HOME = "${tool 'JDK11'}"
+        PATH = "${JAVA_HOME}/bin:${env.PATH}"
     }
 
     parameters {

MIGRATION_NOTES.md

@@ -0,0 +1,80 @@
+# Java 8 to Java 11 Migration Notes
+
+This document summarizes the changes made to migrate the Springboot-BankApp from Java 8 to Java 11.
+
+## Build Configuration Changes
+
+### Maven Compiler Plugin
+The maven-compiler-plugin was updated from version 3.8.0 to 3.11.0 with the following configuration changes:
+
+- Replaced `<source>1.8</source>` and `<target>1.8</target>` with `<release>11</release>`
+- The `release` flag ensures both source compatibility and bytecode target are set consistently
+
+### Java Version Properties
+Updated properties in pom.xml:
+- `java.version`: Changed from 17 to 11
+- Added `maven.compiler.release`: Set to 11
+- Added `project.build.sourceEncoding`: Set to UTF-8
+
+### New Maven Plugins Added
+The following plugins were added to ensure Java 11 compatibility and improve build quality:
+
+- **maven-surefire-plugin** (3.2.5): For running unit tests with Java 11 support
+- **maven-failsafe-plugin** (3.2.5): For running integration tests
+- **maven-enforcer-plugin** (3.5.0): Enforces minimum Java version requirement of 11
+
+## Dependency Updates
+
+### MySQL Connector
+Updated the MySQL connector artifact coordinates to the new reverse-DNS compliant Maven 2+ coordinates:
+- Old: `mysql:mysql-connector-java:8.0.33`
+- New: `com.mysql:mysql-connector-j:8.0.33`
+
+### Test Dependencies
+Added H2 database dependency for testing:
+- `com.h2database:h2` (test scope)
+
+This allows tests to run without requiring a MySQL database connection.
+
+## Test Configuration
+
+### Test Application Properties
+Created `src/test/resources/application.properties` with H2 database configuration for testing:
+- Uses in-memory H2 database (`jdbc:h2:mem:testdb`)
+- Configured with H2Dialect for Hibernate
+- Uses `create-drop` DDL auto mode for clean test isolation
+
+## Removed/Deprecated JDK Modules
+
+No JAXB, JAX-WS, CORBA, or JavaFX dependencies were found in this project. The application does not use any modules that were removed in Java 11.
+
+## Illegal Reflective Access
+
+No illegal reflective access warnings were observed during the build. The application and its dependencies are compatible with Java 11's module system.
+
+## Known Issues and Follow-ups
+
+### JPA Open-in-View Warning
+The following warning appears during tests:
+```
+spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering.
+```
+This is informational and can be addressed by explicitly setting `spring.jpa.open-in-view=false` in application.properties if desired.
+
+### JVM Sharing Warning
+The following warning appears during tests:
+```
+OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
+```
+This is a normal JVM warning when running with certain class loading configurations and does not affect functionality.
+
+## Validation
+
+- Build passes with `mvn clean verify`
+- All tests pass on JDK 11+
+- No illegal reflective access warnings
+- Maven enforcer plugin ensures Java 11+ is required
+
+## Compatibility
+
+This migration targets Java 11 as the minimum version. The application will also run on later LTS versions (Java 17, Java 21) due to backward compatibility.

README.md

@@ -14,6 +14,24 @@
 - ArgoCD (CD)
 - AWS EKS (Kubernetes)
 - Helm (Monitoring using grafana and prometheus)
+
+## Java Requirements
+
+This application requires **Java 11** or later. The build is configured to target Java 11 bytecode and will enforce this minimum version requirement via the Maven Enforcer plugin.
+
+To build and run locally:
+```bash
+# Verify Java version (must be 11+)
+java -version
+
+# Build the application
+./mvnw clean package
+
+# Run tests
+./mvnw test
+```
+
+For detailed migration notes from Java 8 to Java 11, see [MIGRATION_NOTES.md](MIGRATION_NOTES.md).
 
 ### Steps to deploy:
 

pom.xml

@@ -27,7 +27,9 @@
 		<url/>
 	</scm>
 	<properties>
-		<java.version>17</java.version>
+		<java.version>11</java.version>
+		<maven.compiler.release>11</maven.compiler.release>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 	</properties>
 	<dependencies>
 		<dependency>
@@ -52,8 +54,8 @@
 		</dependency>
 
 		<dependency>
-			<groupId>mysql</groupId>
-			<artifactId>mysql-connector-java</artifactId>
+			<groupId>com.mysql</groupId>
+			<artifactId>mysql-connector-j</artifactId>
 			<version>8.0.33</version>
 			<scope>runtime</scope>
 		</dependency>
@@ -67,6 +69,11 @@
 			<artifactId>spring-security-test</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>com.h2database</groupId>
+			<artifactId>h2</artifactId>
+			<scope>test</scope>
+		</dependency>
 	</dependencies>
 
 	<build>
@@ -78,12 +85,41 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-compiler-plugin</artifactId>
-				<version>3.8.0</version>
+				<version>3.11.0</version>
 				<configuration>
-    					<source>1.8</source>
-    					<target>1.8</target>
+					<release>11</release>
+					<compilerArgs>
+						<arg>-Xlint:all</arg>
+					</compilerArgs>
 				</configuration>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<version>3.2.5</version>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-failsafe-plugin</artifactId>
+				<version>3.2.5</version>
+			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-enforcer-plugin</artifactId>
+				<version>3.5.0</version>
+				<executions>
+					<execution>
+						<goals><goal>enforce</goal></goals>
+						<configuration>
+							<rules>
+								<requireJavaVersion>
+									<version>[11,)</version>
+								</requireJavaVersion>
+							</rules>
+						</configuration>
+					</execution>
+				</executions>
+			</plugin>
 		</plugins>
 	</build>
 

src/test/resources/application.properties

@@ -0,0 +1,12 @@
+spring.application.name=bankapp
+
+# H2 Database configuration for testing
+spring.datasource.url=jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
+spring.datasource.driverClassName=org.h2.Driver
+spring.datasource.username=sa
+spring.datasource.password=
+
+# JPA & Hibernate configuration for testing
+spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
+spring.jpa.hibernate.ddl-auto=create-drop
+spring.jpa.show-sql=true