Adjust Java tests to be more forgiving of available JDK images

test/tests/run-java-in-container.sh

@@ -5,15 +5,46 @@ testDir="$(readlink -f "$(dirname "$BASH_SOURCE")")"
 runDir="$(dirname "$(readlink -f "$BASH_SOURCE")")"
 
 image="$1"
-# TODO make this work for ibmjava too (jre or sfj -> sdk)
-jdk="${image/jre/jdk}"
+
+# do a little extra work to try and find a suitable JDK image (when "xyzjava:1.2.3-jre" first builds, "xyzjava:1.2.3-jdk" isn't published yet :D)
+tryJdks=(
+	# ideally, we'd just swap the current JRE image to JDK, but that might not exist yet (see above)
+	"${image/jre/jdk}"
+
+	# try progressively less specific versions to try and find something that can compile an appropriate ".class" object for use in $image (working our way out from "Java 8" because that's going to be the most compatible)
+	"${image%%:*}:8-jdk-slim"
+	"${image%%:*}:8-jdk"
+	"${image%%:*}:jdk-slim"
+	"${image%%:*}:jdk"
+	"${image%%:*}:latest"
+	'openjdk:8-jdk-slim'
+)
+jdk=
+for potentialJdk in "${tryJdks[@]}"; do
+	if docker image inspect "$potentialJdk" &> /dev/null; then
+		jdk="$potentialJdk"
+		break
+	fi
+	if docker pull --quiet "$potentialJdk" &> /dev/null; then
+		jdk="$potentialJdk"
+		break
+	fi
+done
+if [ -z "$jdk" ]; then
+	echo >&2 "error: failed to find a suitable JDK image for '$image'!"
+	exit 1
+fi
+if [ "$jdk" != "${tryJdks[0]}" ]; then
+	echo >&2 "warning: using '$jdk' instead of '${tryJdks[0]}' (results may vary!)"
+fi
 
 newImage="$("$runDir/image-name.sh" librarytest/java-hello-world "$image")"
 "$runDir/docker-build.sh" "$testDir" "$newImage" <<EOD
 FROM $jdk AS jdk
 WORKDIR /container
 COPY dir/container.java ./
-RUN javac ./container.java
+# if possible, use "--release" in case $jdk and $image have mismatching Java versions
+RUN if javac --help 2>&1 | grep -q -- '--release'; then javac --release 8 ./container.java; else javac ./container.java; fi
 FROM $image
 COPY --from=jdk /container /container
 WORKDIR /container