Centos7下"mvn package"命令报错"-bash: mvn: command not found"，安装后报错"NB: JAVA_HOME should point to a JDK not a JRE"

解决办法：
1.linux 安装 maven
2.下载maven安装包

wget --no-check-certificate  https://mirrors.tuna.tsinghua.edu.cn/apache/maven/maven-3/3.6.3/binaries/apache-maven-3.6.3-bin.tar.gz

3.解压maven安装包

tar -xf apache-maven-3.6.3-bin.tar.gz -C /usr/local/
mv /usr/local/apache-maven-3.6.3/ /usr/local/maven3.6

4.配置maven：

vim /etc/profile

在配置文件的尾部中加上：

export MAVEN_HOME=/usr/local/maven3.6/
export PATH=$MAVEN_HOME/bin:$PATH

5.让文件生效，刷新配置文件 ：

source /etc/profile

测试：

mvn -v

报错：

[root@k8s-master-201 maven3.6]# mvn -v
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

报错原因：

"JAVA_HOME should point to a JDK not a JRE",
JAVA_HOME没有指向"JDK"

解决办法：
在centos7中查找"JDK"位置
查找步骤如下：

# which java
/usr/bin/java

# ls -l /usr/bin/java
lrwxrwxrwx. 1 root root 22 Feb 14 19:19 /usr/bin/java -> /etc/alternatives/java

# ls -l /etc/alternatives/java
lrwxrwxrwx. 1 root root 73 Feb 14 19:19 /etc/alternatives/java -> /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.322.b06-1.el7_9.x86_64/jre/bin/java

# ls -l /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.322.b06-1.el7_9.x86_64/jre/bin/java
-rwxr-xr-x. 1 root root 8984 Jan 28 02:05 /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.322.b06-1.el7_9.x86_64/jre/bin/java
# 

可以判断JDK的位置为

"/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.322.b06-1.el7_9.x86_64/jre"

cat -n  /etc/profile | grep "export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL"

然后在文件" /etc/profile"添加JAVA_HOME指向"JDK"
在文件" /etc/profile"的"export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL"下方添加一行

# cat -n  /etc/profile | grep "export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL"
53  export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL
# vim +53 /etc/profile

第53行附近添加3行

export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.322.b06-1.el7_9.x86_64/jre
export PATH=$PATH:$JAVA_HOME/bin
export CLASSPATH=.:$JAVA_HOME/lib/tools.jar:$JAVA_HOME/lib/dt.jar

同时文件末尾添加了3行

MAVEN_HOME=/var/lib/maven/apache-maven-3.6.3 
PATH=$PATH:$MAVEN_HOME/bin
export PATH MAVEN_HOME

备注：

export MAVEN_HOME=/opt/apache-maven-3.5.4  （这个目录换成你的 maven 解压后的文件所在目录）
export PATH=$MAVEN_HOME/bin:$PATH

让文件生效，刷新配置文件 ：
source /etc/profile

5.再次查看maven 版本：

mvn -version
# 或者
mvn -v 

# mvn -v 

Apache Maven 3.6.3 (cecedd343002696d0abb50b32b541b8a6ba2883f)
Maven home: /usr/local/maven3.6
Java version: 1.8.0_322, vendor: Red Hat, Inc., runtime: /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.322.b06-1.el7_9.x86_64/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "3.10.0-1160.el7.x86_64", arch: "amd64", family: "unix"
# 

完整的配置文件如下：

# cat /etc/profile

# /etc/profile

# System wide environment and startup programs, for login setup
# Functions and aliases go in /etc/bashrc

# It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.

pathmunge () {
   case ":${PATH}:" in
       *:"$1":*)
           ;;
       *)
           if [ "$2" = "after" ] ; then
               PATH=$PATH:$1
           else
               PATH=$1:$PATH
           fi
   esac
}


if [ -x /usr/bin/id ]; then
   if [ -z "$EUID" ]; then
       # ksh workaround
       EUID=`/usr/bin/id -u`
       UID=`/usr/bin/id -ru`
   fi
   USER="`/usr/bin/id -un`"
   LOGNAME=$USER
   MAIL="/var/spool/mail/$USER"
fi

# Path manipulation
if [ "$EUID" = "0" ]; then
   pathmunge /usr/sbin
   pathmunge /usr/local/sbin
else
   pathmunge /usr/local/sbin after
   pathmunge /usr/sbin after
fi

HOSTNAME=`/usr/bin/hostname 2>/dev/null`
HISTSIZE=1000
if [ "$HISTCONTROL" = "ignorespace" ] ; then
   export HISTCONTROL=ignoreboth
else
   export HISTCONTROL=ignoredups
fi

export PATH USER LOGNAME MAIL HOSTNAME HISTSIZE HISTCONTROL
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.322.b06-1.el7_9.x86_64/jre
export PATH=$PATH:$JAVA_HOME/bin
export CLASSPATH=.:$JAVA_HOME/lib/tools.jar:$JAVA_HOME/lib/dt.jar


# By default, we want umask to get set. This sets it for login shell
# Current threshold for system reserved uid/gids is 200
# You could check uidgid reservation validity in
# /usr/share/doc/setup-*/uidgid file
if [ $UID -gt 199 ] && [ "`/usr/bin/id -gn`" = "`/usr/bin/id -un`" ]; then
   umask 002
else
   umask 022
fi

for i in /etc/profile.d/*.sh /etc/profile.d/sh.local ; do
   if [ -r "$i" ]; then
       if [ "${-#*i}" != "$-" ]; then 
           . "$i"
       else
           . "$i" >/dev/null
       fi
   fi
done

unset i
unset -f pathmunge

export MAVEN_HOME=/usr/local/maven3.6/
export PATH=$MAVEN_HOME/bin:$PATH