如何在Ubuntu 16服务器上为所有用户安装兼容Tomcat的OpenJDK 9

Hey there, let's resolve this issue where the openjdk-9-internal build from apt is causing Tomcat exceptions. The internal build is an early pre-release with known compatibility bugs—here's how to get a stable, properly supported OpenJDK 9 that works with Tomcat and is accessible to all server users:

Step 1: Remove the problematic internal JDK #

First, fully purge the existing broken installation to avoid conflicts:

sudo apt purge openjdk-9-jdk openjdk-9-jre
sudo apt autoremove && sudo apt clean

Step 2: Install a stable OpenJDK 9 via SDKMAN #

SDKMAN lets you install official, stable OpenJDK distributions (like Adoptium's builds) that are tested for compatibility. Here's how:

1. Install SDKMAN (run this command directly):

   curl -s "https://get.sdkman.io" | bash
   

2. Load SDKMAN into your current shell session:

   source "$HOME/.sdkman/bin/sdkman-init.sh"
   

3. List available stable OpenJDK 9 builds:

   sdk list java
   

   Look for entries marked stable under the Java 9 section (e.g., something like 9.0.7-adpt from Adoptium).
4. Install your chosen stable version (replace 9.0.7-adpt with the actual version from the list):

   sdk install java 9.0.7-adpt
   

5. Set it as your current user's default JDK:

   sdk default java 9.0.7-adpt
   

Step 3: Make the JDK accessible to all users #

To ensure every server user can use this stable JDK, we'll link it to a system-wide path and update alternatives:

1. Get the full path of your installed JDK:

   echo $JAVA_HOME
   

   You'll get a path like /home/your-username/.sdkman/candidates/java/9.0.7-adpt—copy this.
2. Create a system-wide symlink to this path:

   sudo ln -s /home/your-username/.sdkman/candidates/java/9.0.7-adpt /usr/lib/jvm/openjdk-9-stable
   

3. Register the JDK with update-alternatives:

   sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/openjdk-9-stable/bin/java 100
   sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/openjdk-9-stable/bin/javac 100
   

4. Set the new JDK as the system default:

   sudo update-alternatives --config java
   sudo update-alternatives --config javac
   

   When prompted, enter the number corresponding to /usr/lib/jvm/openjdk-9-stable to select it as default.

Step 4: Verify the setup #

• Switch to another user (e.g., su - test-user) and run these commands to confirm the correct version is available:

  java -version
  javac -version
  

  You should see output like this (version numbers may vary slightly):

  openjdk version "9.0.7"
  OpenJDK Runtime Environment AdoptOpenJDK (build 9.0.7+10)
  OpenJDK 64-Bit Server VM AdoptOpenJDK (build 9.0.7+10, mixed mode)

• Start your Tomcat instance and verify the earlier exceptions no longer occur.

Why this works #

The 9-internal build from Ubuntu's repos is an unfinished pre-release, missing critical fixes and compatibility patches required for Tomcat. By switching to a stable, officially supported OpenJDK 9 distribution, you eliminate those compatibility gaps.

内容的提问来源于stack exchange，提问作者Peter Lustig