feat: update java web demo

upack.json

@@ -3,13 +3,15 @@
   "version": "v1alpha2",
   "description": "test java pack",
   "engines": {
-        "build": "adoptopenjdk/openjdk8",
-        "deploy": "adoptopenjdk/openjdk8"
+    "build": "jdk9"
   },
   "build_steps": [
-        "exec ./build.sh", "exec ./clean.sh"
+    "exec ./build.sh",
+    "exec ./clean.sh"
+  ],
+  "deploy_steps": [
+    "exec ./deploy.sh"
   ],
-    "deploy_steps": ["exec ./deploy.sh"],
   "main": "java -jar /app/app.jar",
   "author": "test"
 }