Uses the Debian/Ubuntu update-alternatives system to wire in a Sun/Oracle JDK as preferential

update-alternatives-for-jdk.sh

#! /bin/sh
set -e
# --install link name path priority
# --slave   link name path
## link := the fully-qualified symlink path /usr/bin/java
## name := `basename $link` (for the most part)
## path := the fully-qualified alternative path
## openjdk priority is 1700017

target_java=$1
if test ! -e $target_java
then
    echo "Your target_java ($1) does not exist" >&2
    exit 1
fi
if test ! -x $target_java/bin/java
then
    echo "Your target_java ($1) does not contain java" >&2
    exit 1
fi

target_jre=$target_java/jre
if test ! -d $target_jre
then
    echo "Your target_jre ($target_jre) is not a directory" >&2
    exit 1
fi
if test ! -x $target_jre/bin/java
then
    echo "Your target_jre ($target_jre) does not contain java" >&2
    exit 1
fi
java_version_full=$($target_java/bin/java -version 2>&1 | sed -ne 's/java version "\([^"]*\)"/\1/p')
java_version_triplet=$(echo $java_version_full | sed -e 's/_.*//')

if test -z "$priority"; then
    # ensure ours is the largest number,
    # and openjdk has the "patch number" as 000 not _00 as Sun/Oracle does
    priority=9$(echo $java_version_full | sed -e 's/_/0/' -e 's/[^0-9]//g')
fi

update_java_home_alts() {
    $ECHO update-alternatives --install \
        /usr/lib/jvm/java java_home $target_java $priority
    $ECHO update-alternatives --install \
        /usr/lib/jvm/java-$java_version_triplet java-$java_version_triplet $target_java $priority
    $ECHO update-alternatives --install \
        /usr/lib/jvm/jre jre_home $target_jre $priority
    $ECHO update-alternatives --install \
        /usr/lib/jvm/jre-$java_version_triplet jre-$java_version_triplet $target_jre $priority
}

update_java_bin_alts() {
    for i in /usr/lib/jvm/java/bin/*
    do
        have_man=0
        slave=''
        bn=`basename $i`
        if test '*' == "$bn"; then
            break
        fi
        mf=$bn.1
        mp=/usr/lib/jvm/java/man/man1
        if test -f "$mp/$mf"; then
            have_man=1
        elif test -f "$mp/$mf.gz"; then
            have_man=1
            mf=$mf.gz
        fi
        if test 1 -eq $have_man; then
            slave="--slave /usr/share/man/man1/$mf $mf $mp/$mf"
        fi
        $ECHO update-alternatives --install \
            /usr/bin/$bn $bn $i $priority $slave
    done
}

update_java_home_alts
update_java_bin_alts