java maven 如何知道 JAVA_HOME 在 Ubuntu 中设置为环境变量
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How does maven know JAVA_HOME set as an environment variable inUbuntu
提问by crackerplace
When I type mvn --version in ubuntu from the terminal(ubuntu),I get the below output.
当我从终端（ubuntu）在 ubuntu 中键入 mvn --version 时，我得到以下输出。
Warning: JAVA_HOME environment variable is not set.
Apache Maven 3.0.5
Maven home: /usr/share/maven
Java version: 1.7.0_79, vendor: Oracle Corporation
Java home: /usr/lib/jvm/java-7-openjdk-amd64/jre
Default locale: en_IN, platform encoding: UTF-8
OS name: "linux", version: "3.13.0-32-generic", arch: "amd64", family: "unix"
When I did not set any JAVA_HOME environment variable , how is maven getting the java home installed path.Is it trying to find this path from the /usr/bin/java command which is installed in my system and if so why is it taking the path till jre.
当我没有设置任何 JAVA_HOME 环境变量时，maven 如何获取 java home 安装路径。它是否试图从安装在我系统中的 /usr/bin/java 命令中找到这个路径，如果是这样，为什么它需要直到 jre 的路径。
P.S : Also I could not find any java path in any maven config.
PS：此外，我在任何 Maven 配置中都找不到任何 java 路径。
Thanks.
谢谢。
采纳答案by Zakaria
As showed in the CLIReportingUtils.java(the maven class that retrieves the Java Home), the value comes from the following call :
如CLIReportingUtils.java（检索 Java Home 的 maven 类）所示，该值来自以下调用：
System.getProperty( "java.home", "<unknown java home>" )
The java.homeis for the JRE unlike the JAVA_HOMEwhich is for the JDK.
So Maven is displaying the JRE home.
的java.home是不像的JREJAVA_HOME这对JDK。因此 Maven 正在显示 JRE 主页。
回答by hinneLinks
I would say there is a difference between JAVA_HOMEenvironment variable and the output Java home: /usr/lib/jvm/java-7-openjdk-amd64/jre.
The latter is just the output of the installation directory see here.
我会说JAVA_HOME环境变量和输出之间存在差异 Java home: /usr/lib/jvm/java-7-openjdk-amd64/jre。后者只是安装目录的输出见这里。
So maven will run Java in background and java knows where its installed.
因此 maven 将在后台运行 Java，而 java 知道它的安装位置。
回答by crackerplace
I think,I understand it now.In the maven script i.e (usr/share/maven/bin/mvn) they are trying to find the java installed using a variety of options.
我想，我现在明白了。在 maven 脚本 ie (usr/share/maven/bin/mvn) 中，他们试图找到使用各种选项安装的 java。
So at one place they are doing the below
所以在一个地方他们正在做下面的事情
JAVACMD="`which java`"
And now in my system "which java" points to the below
现在在我的系统中“哪个 java”指向下面
java -> /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java
Hope this is how its getting the java path.
希望这是它获取java路径的方式。
