我已经安装了 Tomcat 11.0.0-M6，每次第一次启动它时都会收到此错误消息：
Error: LinkageError occurred while loading main class org.apache.catalina.startup.Bootstrap java.lang.UnsupportedClassVersionError: org/apache/catalina/startup/Bootstrap has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0
我已经通过执行操作检查了 Java 版本java -version，并且获得了版本 11，对应于 Tomcat 要求的类文件版本 55：
java version "11.0.12" 2021-07-20 LTS Java(TM) SE Runtime Environment 18.9 (build 11.0.12+8-LTS-237) Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.12+8-LTS-237, mixed mode)
然后我这样做了update-alternatives --display java，得到了：
java - manual mode
link best version is /opt/jdk/jdk-11.0.12/bin/java
link currently points to /opt/jdk/jdk-11.0.12/bin/java
link java is /usr/bin/java
/opt/jdk/jdk-11.0.12/bin/java - priority 100
/opt/jdk/jdk-17.0.7/bin/java - priority 100
/opt/jdk/jdk1.8.0_301/bin/java - priority 100
我们可以看到使用的是 Java 11，而不是 Java 17
有 tomcat.service 文件：
[Unit]
Description="Tomcat Service"
After=network.target
[Service]
Type=forking
User=tomcat
Group=tomcat
RestartSec=10
Restart=always
Environment="JAVA_HOME=/opt/jdk/jdk-11.0.12"
Environment="JAVA_OPTS=-Djava.awt.headless=true -Djava.security.egd=file:/dev/./urandom"
Environment="CATALINA_BASE=/opt/tomcat"
Environment="CATALINA_HOME=/opt/tomcat"
Environment="CATALINA_PID=/opt/tomcat/temp/tomcat.pid"
Environment="CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC"
ExecStart=/opt/tomcat/bin/startup.sh
ExecStop=/opt/tomcat/bin/shutdown.sh
[Install]
WantedBy=multi-user.target
[Service]
Environment="CATALINA_OPTS=-Djava.library.path=/usr/java/packages/lib/amd64:/usr/lib/x86_64-linux-gnu:/usr/lib64:/lib64:/lib:/usr/lib"
有人知道是什么导致了这个错误吗？
感谢您的帮助