install the JDK from a local mirror somewhere

jdk-install.sh

#!/bin/bash -e

JDK_MAJOR_VERSION='8'
JDK_MINOR_VERSION='66'
JDK_FILENAME="jdk-${JDK_MAJOR_VERSION}u${JDK_MINOR_VERSION}-linux-x64.tar.gz"
JDK_DOWNLOAD_BASE='http://local-mirror.example.com/miscfiles/'
JDK_DOWNLOAD_URL="${JDK_DOWNLOAD_BASE}${JDK_FILENAME}"

JAVA_BASE_DIR="/opt/java"
JDK_TARBALL="${JAVA_BASE_DIR}/.download/${JDK_FILENAME}"
JDK_HOME="${JAVA_BASE_DIR}/jdk1.${JDK_MAJOR_VERSION}.0_${JDK_MINOR_VERSION}"

CHECKSUM="7e95ad5fa1c75bc65d54aaac9e9986063d0a442f39a53f77909b044cef63dc0a"

function install_symlink() {
  local DEFAULT_JDK_HOME="${JAVA_BASE_DIR}/jdk1.${JDK_MAJOR_VERSION}"
  if [[ "$(readlink "${DEFAULT_JDK_HOME}")" != "${JDK_HOME}" ]]; then
    echo "  Resetting symlink from ${JDK_HOME} ${DEFAULT_JDK_HOME}"
    rm -fr "${DEFAULT_JDK_HOME}"
    ln -sv "${JDK_HOME}" "${DEFAULT_JDK_HOME}"
  fi
  "${DEFAULT_JDK_HOME}/bin/java" -version
}

if [[ ! -d "${JAVA_BASE_DIR}" ]]; then
  echo "  Creating ${JAVA_BASE_DIR}"
  mkdir "${JAVA_BASE_DIR}"
fi

if [[ ! -d "${JAVA_BASE_DIR}/.download" ]]; then
  echo "  Creating ${JAVA_BASE_DIR}/.download"
  mkdir "${JAVA_BASE_DIR}/.download"
fi

echo "  Checking for existence of java jdk1.${JDK_MAJOR_VERSION}.0_${JDK_MINOR_VERSION}"
if [[ ! -x "${JDK_HOME}/bin/java" ]]; then

  if [[ ! -f "${JDK_TARBALL}" ]]; then
    echo "  Downloading jdk1.${JDK_MAJOR_VERSION}.0_${JDK_MINOR_VERSION} from ${JDK_DOWNLOAD_URL}"
    wget --no-cookies --no-check-certificate \
         --output-document="${JDK_TARBALL}" \
         "${JDK_DOWNLOAD_URL}"

    echo "  Checking SHA256 signature of downloaded file"
    if [[ $(sha256sum "" | cut -f1) != "${CHECKSUM}" ]]; then
      echo "  Signature does not match!"
      echo "  Check that the file is correct and that this script is updated correctly!"
      exit 1
    else
      echo "  Signature is OK!"
    fi
  fi

  echo "  Extracting jdk1.${JDK_MAJOR_VERSION}.0_${JDK_MINOR_VERSION} to ${JAVA_BASE_DIR}"
  tar xzf "${JDK_TARBALL}" -C "${JAVA_BASE_DIR}"

  echo "  Changing ownership of ${JDK_HOME}"
  chown -R root:root "${JDK_HOME}"

else
  echo "  Everything looks good!"
fi

install_symlink