remove jenv, only use its download url for java minor version

Author: phith0n

jdk/8u20/Dockerfile

@@ -2,13 +2,14 @@ FROM buildpack-deps:bionic-curl
 
 LABEL maintainer="phithon <root@leavesongs.com>"
 
-ENV JAVA_VERSION "1.8.0_20"
+ENV JAVA_VERSION="1.8.0_20" JAVA_HOME="/opt/jdk"
 
 RUN set -ex \
     && apt-get update \
     && apt-get install -y unzip \
-    && curl -L -s get.jenv.io | bash \
-    && source /root/.jenv/bin/jenv-init.sh \
-    && jenv install java ${JAVA_VERSION} \
+    && cd /opt \
+    && wget http://get.jenv.mvnsearch.org/download/java/java-${JAVA_VERSION}-x64.zip -O /tmp/java.zip \
+    && unzip -q /tmp/java.zip -d /opt \
+    && mv /opt/java-${JAVA_VERSION} /opt/jdk \
     && apt-get autoremove -y --purge unzip \
-    && rm -rf /var/lib/apt/lists/*
+    && rm -rf /var/lib/apt/lists/* /tmp/*