How to Resolve the Error "class file has wrong version 55.0, should be 52.0" When Building Alfresco

What does the error "class file has wrong version 55.0, should be 52.0" mean when building Alfresco?

The error "class file has wrong version 55.0, should be 52.0" indicates a Java version incompatibility in your Alfresco build process. This typically occurs when you try to run code compiled with a newer version of Java on an older JVM that does not support it. Specifically, class file versions represent different Java language levels: version 55 corresponds to Java 11 and version 52 corresponds to Java 8. Thus, the error suggests that your project is configured for Java 8 while using Java 11 compiled classes.

// Set JAVA_HOME in Windows Command Prompt
set JAVA_HOME=C:\Program Files\Java\jdk-11

// Check Java version
java -version

// In Gradle, set Java compatibility
targetCompatibility = '11'
sourceCompatibility = '11'

Causes

• Using a Java version that is incompatible with the classes being used in the project.
• Having multiple Java Development Kit (JDK) versions installed but not setting the correct JAVA_HOME environment variable.
• Building the project with a newer version of Java while attempting to run it on an older Java Runtime Environment (JRE).

Solutions

• Check and update your JAVA_HOME environment variable to point to the correct JDK version you intend to use (Java 11 in this case).
• Ensure that your build configuration in your build tool (like Maven or Gradle) specifies the correct Java source and target compatibility levels appropriate for your project.
• Recompile all classes using Java 11 if newer features have been introduced or if dependencies require it.

Mistake: Not updating the build tools to match the Java version.

Solution: Always verify and update your build tool configurations to align with the Java version you are using.

Mistake: Running an outdated version of Alfresco that does not support the Java version being used.

Solution: Make sure to check Alfresco's documentation for the supported Java versions and upgrade or downgrade as necessary.