jdk版本更换

1.下载安装包

https://www.oracle.com/java/technologies/downloads/archive/

2.上传安装包到java安装路径

3.解压文件夹

cd /usr/java
tar -zxvf jdk-8u102-linux-x64.tar.gz

4.配置环境变量

vi /etc/profile

#增加或修改以下配置
export JAVA_HOME=/usr/java/jdk1.8.0_281
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH

5.让配置生效

source /etc/profile

6.测试是否配置成功

[root@localhost java]# java -version
java version "1.8.0_281"
Java(TM) SE Runtime Environment (build 1.8.0_281-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.281-b09, mixed mode)

tomcat启动或停止依旧使用老版本jdk

• 原因是在tomcat的配置文件里指定了jdk的绝对路径，tomcat就会优先使用自身的配置而非全局变量。

1.查看tomcat/bin/catalina.sh

• 如果有相关配置，修改或去除

cat /home/apache-tomcat-ja/bin/catalina.sh 

# -----------------------------------------------------------------------------
JAVA_HOME=/usr/java/jdk1.8.0_281

2.查看tomcat/bin/setclasspash.sh

cat /home/apache-tomcat-ja/bin/setclasspath.sh

JAVA_HOME=/usr/java/jdk1.8.0_281
JRE_HOME=/usr/java/jdk1.8.0_281/jre

• 修改后重启tomcat

[root@localhost bin]# ./startup.sh 
Using CATALINA_BASE:   /home/apache-tomcat-ja
Using CATALINA_HOME:   /home/apache-tomcat-ja
Using CATALINA_TMPDIR: /home/apache-tomcat-ja/temp
Using JRE_HOME:        /usr/java/jdk1.8.0_281/jre
Using CLASSPATH:       /home/apache-tomcat-ja/bin/bootstrap.jar:/home/apache-tomcat-ja/bin/tomcat-juli.jar
Tomcat started.