Centos 7 安装 JDK 8

JDK_1.8+.png

一般我们在服务器上搭建 Java 应用环境时，都会安装 JDK，因此有必要详细记录下在 Centos 7 下安装 JDK 8。

检查当前系统中的jdk版本

java -version
openjdk version "1.8.0_102"
OpenJDK Runtime Environment (build 1.8.0_102-b14)
OpenJDK 64-Bit Server VM (build 25.102-b14, mixed mode)

查询系统自带openjdk

rpm -qa | grep -i java
java-1.7.0-openjdk-1.7.0.111-2.6.7.8.el7.x86_64
java-1.8.0-openjdk-1.8.0.102-4.b14.el7.x86_64
java-1.8.0-openjdk-headless-1.8.0.102-4.b14.el7.x86_64
java-1.7.0-openjdk-headless-1.7.0.111-2.6.7.8.el7.x86_64

卸载系统自带openjdk

rpm -e --nodeps java-1.7.0-openjdk-1.7.0.111-2.6.7.8.el7.x86_64
rpm -e --nodeps java-1.7.0-openjdk-headless-1.7.0.111-2.6.7.8.el7.x86_64
rpm -e --nodeps java-1.8.0-openjdk-1.8.0.102-4.b14.el7.x86_64
rpm -e --nodeps java-1.8.0-openjdk-headless-1.8.0.102-4.b14.el7.x86_64

或者使用

yum remove *openjdk*

之后再次输入rpm -qa | grep java查看卸载情况

检查当前系统环境

//i686表示32位  x86_64表示是64位
[root@node3]# uname -a
Linux localhost 3.10.0-862.2.3.el7.x86_64 #1 SMP Wed May 9 18:05:47 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

下载

根据操作系统版本，在官网下载相应的tar.gz包

jdk_2019-02-01_22-46-44.png
解压到指定目录:

mkdir -p /usr/local/java 
tar zxvf ../jdk-8u77-linux-x64.tar.gz -C /usr/local/java

配置环境变量

vim /etc/profile

注：如果修改当前用户的环境变量 编辑~/.profile或~/.bashrc文件即可，而不是/etc/profile。
在文件最后添加如下配置：

JAVA_HOME=/usr/local/java/jdk1.8.0_161 
export CLASSPATH=$:CLASSPATH:$JAVA_HOME/lib/ 
export PATH=$PATH:$JAVA_HOME/bin 

重新加载配置文件，使配置生效：

source /etc/profile
或
source ~/.bash_profile

检查是否安装成功

查看 java 安装脚本

java -version
java version “1.8.0_161” 
Java(TM) SE Runtime Environment (build 1.8.0_161-b12) 
Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, mixed mode)

查看执行参数

javac
Usage: javac <options> <source files>
where possible options include:
  -g                         Generate all debugging info
  -g:none                    Generate no debugging info
  -g:{lines,vars,source}     Generate only some debugging info
  -nowarn                    Generate no warnings
  -verbose                   Output messages about what the compiler is doing
  -deprecation               Output source locations where deprecated APIs are used
  -classpath <path>          Specify where to find user class files and annotation processors
  -cp <path>                 Specify where to find user class files and annotation processors
  -sourcepath <path>         Specify where to find input source files
  -bootclasspath <path>      Override location of bootstrap class files
  -extdirs <dirs>            Override location of installed extensions
  -endorseddirs <dirs>       Override location of endorsed standards path
  -proc:{none,only}          Control whether annotation processing and/or compilation is done.
  -processor <class1>[,<class2>,<class3>...] Names of the annotation processors to run; bypasses default discovery process
  -processorpath <path>      Specify where to find annotation processors
  -parameters                Generate metadata for reflection on method parameters
  -d <directory>             Specify where to place generated class files
  -s <directory>             Specify where to place generated source files
  -h <directory>             Specify where to place generated native header files
  -implicit:{none,class}     Specify whether or not to generate class files for implicitly referenced files
  -encoding <encoding>       Specify character encoding used by source files
  -source <release>          Provide source compatibility with specified release
  -target <release>          Generate class files for specific VM version
  -profile <profile>         Check that API used is available in the specified profile
  -version                   Version information
  -help                      Print a synopsis of standard options
  -Akey[=value]              Options to pass to annotation processors
  -X                         Print a synopsis of nonstandard options
  -J<flag>                   Pass <flag> directly to the runtime system
  -Werror                    Terminate compilation if warnings occur
  @<filename>                Read options and filenames from file

出现以上信息则代表安装成功。