在MAC上查找和设置$JAVA_HOME

最近升级了MAC OS，装了JDK7 for mac，在这里下载JDK7 for mac，装完之后发现在默认的路径下找不到JDK7的HOME，如下所示：

$ which java
/usr/bin/java

$ ls -l /usr/bin/java
lrwxr-xr-x 1 root wheel 74 Jan 4 20:24 /usr/bin/java -> /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java

$ ls -l /System/Library/Frameworks/JavaVM.framework/Versions
total 64
lrwxr-xr-x 1 root wheel 10 Jan 4 20:24 1.4 -> CurrentJDK
lrwxr-xr-x 1 root wheel 10 Jan 4 20:24 1.4.2 -> CurrentJDK
lrwxr-xr-x 1 root wheel 10 Jan 4 20:24 1.5 -> CurrentJDK
lrwxr-xr-x 1 root wheel 10 Jan 4 20:24 1.5.0 -> CurrentJDK
lrwxr-xr-x 1 root wheel 10 Jan 4 20:24 1.6 -> CurrentJDK
lrwxr-xr-x 1 root wheel 10 Jan 4 20:24 1.6.0 -> CurrentJDK
drwxr-xr-x 7 root wheel 238 Jan 4 20:25 A
lrwxr-xr-x 1 root wheel 1 Jan 4 20:24 Current -> A
lrwxr-xr-x 1 root wheel 59 Jan 4 20:24 CurrentJDK -> /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents

可是查看java的版本确实是1.7，如下：

$ java -version
java version "1.7.0_45"
Java(TM) SE Runtime Environment (build 1.7.0_45-b18)
Java HotSpot(TM) 64-Bit Server VM (build 24.45-b08, mixed mode)

google了一下，发现了这篇文章Important Java Directories on Mac OS X，可以使用工具命令“/usr/libexec/java_home”来定位JAVA_HOME，这下爽了：

$ cat ~/.profile

JAVA_HOME=`/usr/libexec/java_home`
export JAVA_HOME

$ echo $JAVA_HOME
/Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk/Contents/Home

另外可以使用-V选项列出所有版本的JAVA_HOME：

$ /usr/libexec/java_home -V
Matching Java Virtual Machines (3):
1.7.0_45, x86_64: "Java SE 7" /Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk/Contents/Home
1.6.0_65-b14-462, x86_64: "Java SE 6" /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home
1.6.0_65-b14-462, i386: "Java SE 6" /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home

/Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk/Contents/Home