fix: Replace all unavailable openjdk images with eclipse-temurin:21-jre-alpine

Multiple OpenJDK images (openjdk:latest, openjdk:jre) are no longer available
in Docker Hub, causing E2E test failures across integration tests as shown here: https://github.com/fabric8io/docker-maven-plugin/actions/runs/19297563136/job/55183715105?pr=1888

Fixed all references:
- it/helloworld/pom.xml: openjdk:latest → eclipse-temurin:21-jre-alpine
- it/run-java/Dockerfile: openjdk:jre → eclipse-temurin:21-jre-alpine
- it/zero-config/Dockerfile: openjdk:jre → eclipse-temurin:21-jre-alpine
- samples/helloworld/pom.xml: openjdk:latest → eclipse-temurin:21-jre-alpine
- samples/run-java/Dockerfile: openjdk:jre → eclipse-temurin:21-jre-alpine
- samples/zero-config/Dockerfile: openjdk:jre → eclipse-temurin:21-jre-alpine
- Test data: Dockerfile_multi_stage_with_args and corresponding test expectation

eclipse-temurin:21-jre-alpine provides:
- Official OpenJDK distribution (Eclipse Adoptium)
- Lightweight Alpine-based image (~80MB vs ~400MB)
- Java 21 JRE functionality for all test scenarios

This resolves test failures like:
HttpRequestException: manifest for openjdk:latest not found: manifest unknown

Signed-off-by: Ganesh Gautam <[email protected]>

Author: Ganeshgautam

it/helloworld/pom.xml

@@ -41,7 +41,7 @@
               <name>hello/sub/project/java:${project.version}</name>
               <alias>hello-world</alias>
               <build>
-                <from>openjdk:latest</from>
+                <from>eclipse-temurin:21-jre-alpine</from>
                 <assembly>
                   <descriptorRef>artifact</descriptorRef>
                 </assembly>

it/run-java/Dockerfile

@@ -1,4 +1,4 @@
-FROM openjdk:jre
+FROM eclipse-temurin:21-jre-alpine
 
 ADD target/${project.build.finalName}.jar /opt/hello-world.jar
 ADD target/docker-extra/run-java/run-java.sh /opt

it/zero-config/Dockerfile

@@ -1,4 +1,4 @@
-FROM openjdk:jre
+FROM eclipse-temurin:21-jre-alpine
 
 #RUN VERSION=$(mvn -q -Dexec.executable=echo -Dexec.args='${project.version}' --non-recursive exec:exec)
 ARG jar_file=target/dmp-it-zero-config-${project.version}.jar

samples/helloworld/pom.xml

@@ -38,7 +38,7 @@
               <name>hello/sub/project/java:${project.version}</name>
               <alias>hello-world</alias>
               <build>
-                <from>openjdk:latest</from>
+                <from>eclipse-temurin:21-jre-alpine</from>
                 <assembly>
                   <descriptorRef>artifact</descriptorRef>
                 </assembly>

samples/run-java/Dockerfile

@@ -1,4 +1,4 @@
-FROM openjdk:jre
+FROM eclipse-temurin:21-jre-alpine
 
 ADD target/${project.build.finalName}.jar /opt/hello-world.jar
 ADD target/docker-extra/run-java/run-java.sh /opt

samples/zero-config/Dockerfile

@@ -1,4 +1,4 @@
-FROM openjdk:jre
+FROM eclipse-temurin:21-jre-alpine
 
 ARG jar_file=target/dmp-sample-zero-config.jar
 

src/test/java/io/fabric8/maven/docker/util/DockerFileUtilTest.java

@@ -110,7 +110,7 @@ void testMultiStageWithArgs() throws Exception {
 
         Assertions.assertEquals("fabric8/s2i-java:latest", fromClauses.next());
         Assertions.assertEquals("busybox:latest", fromClauses.next());
-        Assertions.assertEquals("docker.io/library/openjdk:latest", fromClauses.next());
+        Assertions.assertEquals("docker.io/library/eclipse-temurin:latest", fromClauses.next());
         Assertions.assertFalse(fromClauses.hasNext());
     }
 

src/test/resources/io/fabric8/maven/docker/util/Dockerfile_multi_stage_with_args

@@ -3,5 +3,5 @@ FROM fabric8/s2i-java:$VERSION AS BUILD
 ARG FULL_IMAGE=busybox:latest
 FROM $FULL_IMAGE AS DEPLOYABLE
 ARG REPO_1:docker.io/library
-ARG IMAGE-1:openjdk
+ARG IMAGE-1:eclipse-temurin
 FROM $REPO_1/${IMAGE-1}:$VERSION