【ElasticSearch】執行ES命令時，報`require Java 11`

future versions of Elasticsearch will require Java 11; your Java version from [/usr/local/jdk1.8.0_1/jre] does not meet this requirement

使用ES7版本時，啟動或者執行ES命令，提示上面錯誤信息。這是由於ES7使用的高版本的jdk。如果不想升級服務的jdk，可以通過修改elasticsearch-env配置文件，使用ES內置的jdk來解決上面的問題。

# now set the path to java
# 注釋掉原來的配置信息
#if [ ! -z "$JAVA_HOME" ]; then
#  JAVA="$JAVA_HOME/bin/java"
#  JAVA_TYPE="JAVA_HOME"
#else
#  if [ "$(uname -s)" = "Darwin" ]; then
#    # macOS has a different structure
#    JAVA="$ES_HOME/jdk.app/Contents/Home/bin/java"
#  else
#    JAVA="$ES_HOME/jdk/bin/java"
#  fi
#  JAVA_TYPE="bundled jdk"
#fi
# 如何為新的配置信息
if [ ! -z "$JAVA_HOME" ]; then
  JAVA="$ES_HOME/jdk/bin/java"
  JAVA_TYPE="JAVA_HOME"
else
  if [ "$(uname -s)" = "Darwin" ]; then
    # macOS has a different structure
    JAVA="$ES_HOME/jdk.app/Contents/Home/bin/java"
  else
    JAVA="$ES_HOME/jdk/bin/java"
  fi  
  JAVA_TYPE="bundled jdk"
fi