add java to pmmlserver, add testing instructions

pmmlserver/README.md

@@ -0,0 +1,32 @@
+## Testing instructions
+
+From the [upstream usage example](https://kserve.github.io/website/master/modelserving/v1beta1/pmml/), this rock can be tested locally using:
+
+Launch the server with:
+```
+# download the model locally
+mkdir sample_model
+gsutil cp -r gs://kfserving-examples/models/pmml ./sample_model/
+
+# mount the model into the container at runtime
+docker run -p 8080:8080 -v $(pwd)/sample_model/pmml:/mnt/models pmmlserver:0.11.2 --model_name test_model --model_dir=/mnt/models --http_port=8080
+
+```
+
+Test the server with:
+```
+cat <<EOF >> input.json
+{
+  "instances": [
+    [5.1, 3.5, 1.4, 0.2]
+  ]
+}
+EOF
+
+curl -v \
+  -H "Content-Type: application/json" \
+  -d @./input.json \
+  localhost:8080/v1/models/test_model:predict
+```
+
+which should return the expected output described in the docs.  

pmmlserver/rockcraft.yaml

@@ -29,6 +29,16 @@ parts:
       dpkg-query --root=${CRAFT_PROJECT_DIR}/../bundles/ubuntu-22.04/rootfs/ -f '${db:Status-Abbrev},${binary:Package},${Version},${source:Package},${Source:Version}\n' -W) \
       > ${CRAFT_PART_INSTALL}/usr/share/rocks/dpkg.query
 
+  java:
+    plugin: nil
+    build-packages:
+      - default-jdk
+    stage-packages:
+      - default-jdk
+    # Also stage the links for java executable
+    override-build:
+      ln -s /usr/lib/jvm/java-11-openjdk-amd64/bin/java $CRAFT_PART_INSTALL/usr/bin/java
+
   python:
     plugin: nil
     source: https://github.com/kserve/kserve.git