Use JDK 21

.github/workflows/maven.yml

@@ -23,10 +23,10 @@ jobs:
     - uses: actions/checkout@v3
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-    - name: Set up JDK 17
+    - name: Set up JDK 21
       uses: actions/setup-java@v3 # https://github.com/actions/setup-java
       with:
-        java-version: '17'
+        java-version: '21'
         distribution: 'temurin'
         cache: maven
     - name: Build with Maven

Dockerfile

@@ -6,7 +6,7 @@
 ###############################################################################
 # Stage 1 (to create a "build" image, ~360MB)                                 #
 ###############################################################################
-FROM eclipse-temurin:17-jdk-alpine AS builder
+FROM eclipse-temurin:21-jdk-alpine AS builder
 
 # Smoke test to verify if java is available.
 RUN java -version
@@ -29,7 +29,7 @@ WORKDIR /usr/src/myapp/
 RUN ./mvnw package
 
 ###############################################################################
-# Stage 2 (to create a downsized "container executable", ~117MB)              #
+# Stage 2 (to create a downsized "container executable", ~131MB)              #
 ###############################################################################
 FROM alpine:latest
 ENV JAVA_HOME=/jre

README.md

@@ -15,7 +15,7 @@ Features:
 - The Docker build uses a
   [multi-stage build setup](https://docs.docker.com/build/building/multi-stage/)
   including a downsized JRE (built inside Docker via `jlink`)
-  to minimize the size of the generated Docker image, which is **117MB**.
+  to minimize the size of the generated Docker image, which is **131MB**.
 - Supports [Docker BuildKit](https://docs.docker.com/build/)
 - Supports GraalVM to create
   [native images](https://www.graalvm.org/latest/reference-manual/native-image/)
@@ -24,7 +24,7 @@ Features:
   intentionally does not use these native app images because the majority of
   Java developers do not use GraalVM. If you do want to use native images,
   please modify [Dockerfile](Dockerfile) accordingly.
-- Java 17 (Eclipse Temurin)
+- Java 21 (Eclipse Temurin)
 - [JUnit 5](https://github.com/junit-team/junit5) for demonstrating how to integrate unit testing
 - Maven for build management, using [Maven Wrapper](https://github.com/apache/maven-wrapper)
 - [GitHub Actions workflows](https://github.com/miguno/java-docker-build-tutorial/actions) for
@@ -114,7 +114,7 @@ $ just docker-image-create
 # Notes
 
 You can also build, test, package, and run the Java application locally
-(without Docker) if you have JDK 17+ installed. You do not need to have Maven
+(without Docker) if you have JDK 21+ installed. You do not need to have Maven
 installed, because this repository contains the
 [Maven Wrapper](https://github.com/apache/maven-wrapper) `mvnw` (use `mvnw.cmd`
 on Windows).

pom.xml

@@ -21,7 +21,7 @@
 
   <properties>
     <compiler-plugin.version>3.13.0</compiler-plugin.version>
-    <java.version>17</java.version>
+    <java.version>21</java.version>
     <maven.compiler.parameters>true</maven.compiler.parameters>
     <maven.compiler.release>${java.version}</maven.compiler.release>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>