Not able to change the JDK in Mac OS using Jenv

问题

I am using Amazon corretto JDK and earlier had only 1.8 installed in my Mac OS, yesterday I installed Amazon corretto JDK 11 using the Mac OS package installer and after that it changed my default java version to 11.

I followed highly rated medium blog on Jenv to manage multiple version on Mac OS but still my default java version is not switching back to 1.8 and didn't get any error while following stackoverflow answer or medium post.

command using Jenv

jenv versions

  system
  1.8
* 1.8.0.252 (set by /Users/my user/.jenv/version) // note `*` that should tell the current version IMO
  11
  11.0
  11.0.7
  corretto64-1.8.0.252
  corretto64-11.0.7

output of java -version

java --version openjdk 11.0.7 2020-04-14 LTS OpenJDK Runtime Environment Corretto-11.0.7.10.1 (build 11.0.7+10-LTS) OpenJDK 64-Bit Server VM Corretto-11.0.7.10.1 (build 11.0.7+10-LTS, mixed mode)

Note: I have multiple apps which used different JDK versions and I don't want to use the alias way of managing the JDK version, I am interested in Jenv where I can set my JDK version globally(1.8 in my case) and locally(based on the JDK particular app uses).

回答1:

Try adding this to your .bash_profile or .zshrc or .bashrc whatever is relevant to your macOS.

jdk() {
        version=$1
        export JAVA_HOME=$(/usr/libexec/java_home -v"$version");
        java -version
 }

Then, restart terminal and you can switch java versions like:

jdk 1.8
jdk 11

回答2:

Behind the scenes jenv uses the /Library/Java/JavaVirtualMachines directory.

Then you could also type /usr/libexec/java_home -V to show all the available JDKs and analyse your issue:

Matching Java Virtual Machines (4): 
11.0.2_2-OracleJDK, x86_64: "Java SE 11.0.2" /Library/Java/JavaVirtualMachines/OracleJDK-jdk-11.0.2.jdk/Contents/Home 
11.0.2_1-OpenJDK, x86_64: "OpenJDK 11.0.2" /Library/Java/JavaVirtualMachines/OpenJDK-jdk-11.0.2.jdk/Contents/Home 
1.8.0_11, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_11.jdk/Contents/Home 
1.7.0_45, x86_64: "Java SE 7" /Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk/Contents/Home 

/Library/Java/JavaVirtualMachines/OracleJDK-jdk-11.0.2.jdk/Contents/Home

In this exemple export JAVA_HOME=$(/usr/libexec/java_home -v 1.8) set the JDK 1.8 version.

Thus, you even could define the following aliases:

java11_OpenJDK_export='export JAVA_HOME=$(/usr/libexec/java_home -v 11.0.2_1-OpenJDK)'
java11_OracleJDK_export='export JAVA_HOME=$(/usr/libexec/java_home -v 11.0.2_2-OracleJDK)'
java7_export='export JAVA_HOME=$(/usr/libexec/java_home -v 1.7)'
java8_export='export JAVA_HOME=$(/usr/libexec/java_home -v 1.8)'

NB: The version to use after java_home -v is defined in each JDK installation in the Contents/Info.plist file section JVMVersion.

I changed it, to easily switch between the OpenJDK and the Oracle JDK:

$ tail -5 /Library/Java/JavaVirtualMachines/OpenJDK-jdk-11.0.2.jdk/Contents/Info.plist | head -2
<key>JVMVersion</key>
<string>11.0.2_1-OpenJDK</string>

$ tail -5 /Library/Java/JavaVirtualMachines/OracleJDK-jdk-11.0.2.jdk/Contents/Info.plist | head -2
<key>JVMVersion</key>
<string>11.0.2_2-OracleJDK</string>

So, in your case as you have two 1.8 versions (1.8 and 1.8.0.252). It is more than likely that you should update their Contents/Info.plist file section JVMVersion.

来源：https://stackoverflow.com/questions/62017152/not-able-to-change-the-jdk-in-mac-os-using-jenv

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