啟動tomcat情況如下：
root@ubuntu:/usr/local/tomcat/apache-tomcat-8.5.20/bin# ./catalina.sh
Using CATALINA_BASE: /usr/local/tomcat/apache-tomcat-8.5.20
Using CATALINA_HOME: /usr/local/tomcat/apache-tomcat-8.5.20
Using CATALINA_TMPDIR: /usr/local/tomcat/apache-tomcat-8.5.20/temp
Using JRE_HOME: /usr/local/java/jdk1.8.0_144
Using CLASSPATH: /usr/local/tomcat/apache-tomcat-8.5.20/bin/bootstrap.jar:/usr/local/tomcat/apache-tomcat-8.5.20/bin/tomcat-juli.jar
Usage: catalina.sh ( commands ... )
commands:
debug Start Catalina in a debugger
debug -security Debug Catalina with a security manager
jpda start Start Catalina under JPDA debugger
run Start Catalina in the current window
run -security Start in the current window with security manager
start Start Catalina in a separate window
start -security Start in a separate window with security manager
stop Stop Catalina, waiting up to 5 seconds for the process to end
stop n Stop Catalina, waiting up to n seconds for the process to end
stop -force Stop Catalina, wait up to 5 seconds and then use kill -KILL if still running
stop n -force Stop Catalina, wait up to n seconds and then use kill -KILL if still running
configtest Run a basic syntax check on server.xml - check exit code for result
version What version of tomcat are you running?
Note: Waiting for the process to end and use of the -force option require that $CATALINA_PID is defined
在一個網站上看到說這個是因為環境變量的問題，tomcat使用的環境變量是自己的或者是繼承自當前用戶的，所以在Linux里面即使你設置了java_home也不一定會用這個，所以要么你都繼承root的環境變量，都統一起來確保你的系統里面的環境變量都是使用的同一個，要么就單獨指定要使用的jdk。tomcat啟動的時候需要盜用setclasspath.sh。只要在setclasspath.sh聲明環境變量就可以知道你這個tomcat使用哪個jdk，打開tomcat的bin目錄下面的setclasspath.sh，添加上，路徑自己修改，添加在開頭就行
export JAVA_HOME=/usr/local/java/jdk1.8.0_144
export JRE_HOME=/usr/local/java/jdk1.8.0_144/jre
然后重啟tomcat就可以使用了
這樣可使配置不同的tomcat使用不同的jdk