1. 编译报错：java.nio.file.NoSuchFileException
在编译 Jenkins 插件时，提示错误信息如下：
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| mvn package
Compilation failure
[ERROR] java.nio.file.NoSuchFileException: /root/java/target/classes/META-INF/annotations/hudson.Extension
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原来 Maven 使用的是 JAVA_HOME 而不是 PATH，找不到 Java 运行环境导致，而且 Java 11 不行，Java 1.8 才能正常编译。
2. 安装 JDK
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| yum install -y java-11-openjdk-devel
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| yum install -y java-1.8.0-openjdk-devel
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3. 选择 JDK 版本
选择当前 JDK 版本：
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| alternatives --config java
There are 2 programs which provide 'java'.
Selection Command
-----------------------------------------------
1 java-11-openjdk.x86_64 (/usr/lib/jvm/java-11-openjdk-11.0.7.10-4.el7_8.x86_64/bin/java)
*+ 2 java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64/jre/bin/java)
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选择 2 之后， /usr/lib/jvm/java-openjdk 即为当前选择的版本。
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| ls -l /usr/lib/jvm
lrwxrwxrwx 1 root root 26 Jul 1 15:42 java -> /etc/alternatives/java_sdk
lrwxrwxrwx 1 root root 29 Jul 1 15:42 java-11 -> /etc/alternatives/java_sdk_11
lrwxrwxrwx 1 root root 37 Jul 1 15:42 java-11-openjdk -> /etc/alternatives/java_sdk_11_openjdk
drwxr-xr-x 8 root root 4096 Jul 1 15:42 java-11-openjdk-11.0.7.10-4.el7_8.x86_64
lrwxrwxrwx 1 root root 34 Jul 1 15:42 java-openjdk -> /etc/alternatives/java_sdk_openjdk
lrwxrwxrwx 1 root root 21 Jul 1 16:01 jre -> /etc/alternatives/jre
lrwxrwxrwx 1 root root 24 Jul 1 15:42 jre-11 -> /etc/alternatives/jre_11
lrwxrwxrwx 1 root root 32 Jul 1 15:42 jre-11-openjdk -> /etc/alternatives/jre_11_openjdk
lrwxrwxrwx 1 root root 40 Jul 1 15:42 jre-11-openjdk-11.0.7.10-4.el7_8.x86_64 -> java-11-openjdk-11.0.7.10-4.el7_8.x86_64
lrwxrwxrwx 1 root root 29 Jul 1 15:42 jre-openjdk -> /etc/alternatives/jre_openjdk
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查看 Java 版本：
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| java -version
openjdk version "1.8.0_252"
OpenJDK Runtime Environment (build 1.8.0_252-b09)
OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode
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4. 配置环境变量
编辑文件
添加环境变量
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| export JAVA_HOME=/usr/lib/jvm/java-openjdk
export JRE_HOME=/usr/lib/jvm/jre-openjdk
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使环境变量生效
5. 卸载 JDK
查看当前环境安装的 JDK :
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| rpm -aq | grep -i jdk
copy-jdk-configs-3.3-10.el7_5.noarch
java-1.8.0-openjdk-headless-1.8.0.252.b09-2.el7_8.x86_64
java-11-openjdk-headless-11.0.7.10-4.el7_8.x86_64
java-11-openjdk-devel-11.0.7.10-4.el7_8.x86_64
java-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64
java-11-openjdk-11.0.7.10-4.el7_8.x86_64
java-1.8.0-openjdk-devel-1.8.0.252.b09-2.el7_8.x86_64
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不需要一个一个删除，只需要删除 copy-jdk-configs 即可。
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| yum remove -y copy-jdk-configs-3.3-10.el7_5.noarch
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