Added support for Java 7

Dockerfile

@@ -1,4 +1,4 @@
-FROM adoptopenjdk:16-jre
+FROM openjdk:7-jre
 
 LABEL org.opencontainers.image.authors="Geoff Bourne <itzgeoff@gmail.com>"
 
@@ -6,7 +6,6 @@ RUN apt-get update \
   && DEBIAN_FRONTEND=noninteractive \
   apt-get install -y \
     imagemagick \
-    gosu \
     sudo \
     net-tools \
     curl wget \
@@ -22,6 +21,42 @@ RUN apt-get update \
     ttf-dejavu \
     && apt-get clean
 
+# Procedure from https://github.com/tianon/gosu/blob/master/INSTALL.md#from-debian
+ENV GOSU_VERSION 1.14
+RUN set -eux; \
+# save list of currently installed packages for later so we can clean up
+	savedAptMark="$(apt-mark showmanual)"; \
+	apt-get update; \
+	apt-get install -y --no-install-recommends ca-certificates wget; \
+	if ! command -v gpg; then \
+		apt-get install -y --no-install-recommends gnupg2 dirmngr; \
+	elif gpg --version | grep -q '^gpg (GnuPG) 1\.'; then \
+# "This package provides support for HKPS keyservers." (GnuPG 1.x only)
+		apt-get install -y --no-install-recommends gnupg-curl; \
+	fi; \
+	rm -rf /var/lib/apt/lists/*; \
+	\
+	dpkgArch="$(dpkg --print-architecture | awk -F- '{ print $NF }')"; \
+	wget -O /usr/local/bin/gosu "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$dpkgArch"; \
+	wget -O /usr/local/bin/gosu.asc "https://github.com/tianon/gosu/releases/download/$GOSU_VERSION/gosu-$dpkgArch.asc"; \
+	\
+# verify the signature
+	export GNUPGHOME="$(mktemp -d)"; \
+	gpg --batch --keyserver hkps://keys.openpgp.org --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4; \
+	gpg --batch --verify /usr/local/bin/gosu.asc /usr/local/bin/gosu; \
+	command -v gpgconf && gpgconf --kill all || :; \
+	rm -rf "$GNUPGHOME" /usr/local/bin/gosu.asc; \
+	\
+# clean up fetch dependencies
+	apt-mark auto '.*' > /dev/null; \
+	[ -z "$savedAptMark" ] || apt-mark manual $savedAptMark; \
+	apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+	\
+	chmod +x /usr/local/bin/gosu; \
+# verify that the binary works
+	gosu --version; \
+	gosu nobody true
+
 RUN addgroup --gid 1000 minecraft \
   && adduser --system --shell /bin/false --uid 1000 --ingroup minecraft --home /data minecraft