Linux 命令行搭建Java环境

当Linux不启用图形界面的时候，我们只能通过命令行来搭建Java环境了。

平台： CentOS 6.5

1. 下载

不知道后续Oracle公司会不会会不会更新网址，所以以当前时间(2016年7月19日)为例。如果我们有浏览器，只需要输入以下网址：

http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

就能打开Java jdk 的下载页面了。然后下载即可。

下载的时候需要点击“Accept License Agreement ”，所以用这个命令：

wget http://download.oracle.com/otn-pub/java/jdk/8u91-b14/jdk-8u91-linux-x64.tar.gz[/code] 
下载下来的文件只有5K左右，只是一个一个HTML文件罢了。所以需要输入以下命令：

wget --no-check-certificate --no-cookies --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u91-b14/jdk-8u91-linux-x64.tar.gz[/code] 
这样就能下载jdk-8u91-linux-x64.tar.gz 这个压缩包了。

2. 解压
建立一个目录，如我这里建的目录是
/usr/java/jdk8
。

mkdir /usr/java
mkdir /usr/java/jdk8


利用以下命令解压刚才下载的
jdk-8u91-linux-x64.tar.gz
压缩包。进入这个压缩包所在的目录，然后输入以下命令：

tar zxvf jdk-8u91-linux-x64.tar.gz -C /usr/java/jdk8/


解压之后
/usr/java/jdk8/
目录下有一个目录：
jdk1.8.0_91
。这就是JDK的安装目录。

3. 设置环境变量
修改配置文件:

vim ~/.bashrc


在文件中加入：

export JAVA_HOME=/usr/java/jdk8/jdk1.8.0_91/
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH


然后输入命令让配置文件生效：

source ~/.bashrc


4. 测试
可以输入
java
和
javac
这两个命令测试一下。

输入
java
输出结果：

Usage: java [-options] class [args...]
(to execute a class)
or  java [-options] -jar jarfile [args...]
(to execute a jar file)
where options include:
-d32      use a 32-bit data model if available
-d64      use a 64-bit data model if available
-server   to select the "server" VM
The default VM is server.

-cp <class search path of directories and zip/jar files>
-classpath <class search path of directories and zip/jar files>
A : separated list of directories, JAR archives,
and ZIP archives to search for class files.
-D<name>=<value>
set a system property
-verbose:[class|gc|jni]
enable verbose output
-version      print product version and exit
-version:<value>
Warning: this feature is deprecated and will be removed
in a future release.
require the specified version to run
-showversion  print product version and continue
-jre-restrict-search | -no-jre-restrict-search
Warning: this feature is deprecated and will be removed
in a future release.
include/exclude user private JREs in the version search
-? -help      print this help message
-X            print help on non-standard options
-ea[:<packagename>...|:<classname>]
-enableassertions[:<packagename>...|:<classname>]
enable assertions with specified granularity
-da[:<packagename>...|:<classname>]
-disableassertions[:<packagename>...|:<classname>]
disable assertions with specified granularity
-esa | -enablesystemassertions
enable system assertions
-dsa | -disablesystemassertions
disable system assertions
-agentlib:<libname>[=<options>]
load native agent library <libname>, e.g. -agentlib:hprof
see also, -agentlib:jdwp=help and -agentlib:hprof=help
-agentpath:<pathname>[=<options>]
load native agent library by full pathname
-javaagent:<jarpath>[=<options>]
load Java programming language agent, see java.lang.instrument
-splash:<imagepath>
show splash screen with specified image
See http://www.oracle.com/technetwork/java/javase/documentation/index.html for more details.


输入
javac
 的输出结果：

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</span>


那就说明Java环境已经搭建好了。