Improve Java Hello World (#1111)

* Use AdoptOpenJDK for newest version of JDK that has proper container support.
Upgraded Spring Boot version.

* updated to AdoptOpenJDK

docs/serving/samples/hello-world/helloworld-java/.dockerignore

@@ -0,0 +1 @@
+target/

docs/serving/samples/hello-world/helloworld-java/Dockerfile

@@ -10,10 +10,11 @@ COPY src ./src
 # Build a release artifact.
 RUN mvn package -DskipTests
 
-# Use the Official OpenJDK image for a lean production stage of our multi-stage build.
+# Use AdoptOpenJDK for base image.
-# https://hub.docker.com/_/openjdk
+# It's important to use OpenJDK 8u191 or above that has container support enabled.
+# https://hub.docker.com/r/adoptopenjdk/openjdk8
 # https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds
-FROM openjdk:8-jre-alpine
+FROM adoptopenjdk/openjdk8:jdk8u202-b08-alpine-slim
 
 # Copy the jar to the production image from the builder stage.
 COPY --from=builder /app/target/helloworld-*.jar /helloworld.jar

docs/serving/samples/hello-world/helloworld-java/README.md

@@ -97,10 +97,11 @@ recreate the source files from this folder.
    # Build a release artifact.
    RUN mvn package -DskipTests
 
-   # Use the Official OpenJDK image for a lean production stage of our multi-stage build.
+   # Use AdoptOpenJDK for base image.
-   # https://hub.docker.com/_/openjdk
+   # It's important to use OpenJDK 8u191 or above that has container support enabled.
+   # https://hub.docker.com/r/adoptopenjdk/openjdk8
    # https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds
-   FROM openjdk:8-jre-alpine
+   FROM adoptopenjdk/openjdk8:jdk8u202-b08-alpine-slim
 
    # Copy the jar to the production image from the builder stage.
    COPY --from=builder /app/target/helloworld-*.jar /helloworld.jar

docs/serving/samples/hello-world/helloworld-java/pom.xml

@@ -14,7 +14,7 @@
 	<parent>
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-starter-parent</artifactId>
-		<version>2.0.3.RELEASE</version>
+		<version>2.1.3.RELEASE</version>
 		<relativePath/> <!-- lookup parent from repository -->
 	</parent>
 

docs/serving/samples/hello-world/helloworld-kotlin/Dockerfile

@@ -9,10 +9,11 @@ COPY src ./src
 # Build a release artifact.
 RUN gradle clean build --no-daemon
 
-# Use the Official OpenJDK image for a lean production stage of our multi-stage build.
+# Use AdoptOpenJDK for base image.
-# https://hub.docker.com/_/openjdk
+# It's important to use OpenJDK 8u191 or above that has container support enabled.
+# https://hub.docker.com/r/adoptopenjdk/openjdk8
 # https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds
-FROM openjdk:8-jre-alpine
+FROM adoptopenjdk/openjdk8:jdk8u202-b08-alpine-slim
 
 # Copy the jar to the production image from the builder stage.
 COPY --from=builder /home/gradle/build/libs/gradle.jar /helloworld.jar

docs/serving/samples/hello-world/helloworld-kotlin/README.md

@@ -118,10 +118,11 @@ recreate the source files from this folder.
    # Build a release artifact.
    RUN gradle clean build --no-daemon
 
-   # Use the Official OpenJDK image for a lean production stage of our multi-stage build.
+   # Use AdoptOpenJDK for base image.
-   # https://hub.docker.com/_/openjdk
+   # It's important to use OpenJDK 8u191 or above that has container support enabled.
+   # https://hub.docker.com/r/adoptopenjdk/openjdk8
    # https://docs.docker.com/develop/develop-images/multistage-build/#use-multi-stage-builds
-   FROM openjdk:8-jre-alpine
+   FROM adoptopenjdk/openjdk8:jdk8u202-b08-alpine-slim
 
    # Copy the jar to the production image from the builder stage.
    COPY --from=builder /home/gradle/build/libs/gradle.jar /helloworld.jar