我正在尝试安装DSpace 6.3在 Ubuntu 18.04 上，当我尝试编译 maven 时，我现在收到以下消息：
becsadspace@becsadspace-OptiPlex-780:~$ mvn -U package
The JAVA_HOME environment variable is not defined correctly
This environment variable is needed to run this program
NB: JAVA_HOME should point to a JDK not a JRE