Fixing Gradle's wsdl2java Plugin: Upgrading Apache CXF to Ensure Java Compatibility

Learn how to troubleshoot and fix compatibility issues with the `wsdl2java` Gradle plugin when migrating to Java 11 while using Apache CXF.
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Fixing Gradle's wsdl2java Plugin: Upgrading Apache CXF to Ensure Java Compatibility

If you're working with Gradle and the wsdl2java plugin, you may have encountered some compatibility issues when trying to build your project with Java 11. This issue often arises as a result of the migration from the javax namespace to the jakarta namespace, which can leave developers scratching their heads as they try to resolve class loading errors. In this guide, we will explore common errors related to the no.nils.wsdl2java plugin and, more importantly, present a solution to fix these problems and allow your project to build seamlessly.

The Problem: Compatibility Issues with Java Versions

When using the wsdl2java Gradle plugin, many developers have reported error messages related to class loading and version incompatibility. The two most common errors include:

JAXB Exception:

"Unable to load class 'jakarta.xml.bind.JAXBException'" when compiling with Java 11.

Class File Version Error:

"org/apache/cxf/tools/wsdlto/WSDLToJava has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0." when compiling with Java 8.

These errors highlight the complications that can arise from the version dependencies of Apache CXF and your current Java version. With Java 8, your project may try to load classes compiled with Java 11, leading to clashes in expected Java Runtime Environment (JRE) versions.

Linking the Issue to Apache CXF Version

The underlying problem is that the version of the cxf-tools-wsdlto library that your project depends on may not be compatible with Java 8. Specifically, the error suggests that the class WSDLToJava is compiled with a version not supported by Java 8. The dependency tree of your project can often point you to the exact source of this inconsistency.

How to Check the Dependency Tree

To get started, you can check the dependency tree for your wsdl2java configuration by running the following command in your terminal:

[[See Video to Reveal this Text or Code Snippet]]

This command will provide a detailed list of dependencies and their versions, allowing you to identify which version of org.apache.cxf is being used. You might see something like:

[[See Video to Reveal this Text or Code Snippet]]

This indicates that the plugin is pulling the latest version of the cxf-tools-wsdlto-databinding-jaxb, which in this case is 4.0.0, incompatible with Java 8.

The Solution: Specify an Older Version of Apache CXF

To solve this problem, you can explicitly specify an older version of the Apache CXF that is compatible with Java 8. Here is how you can modify your build.gradle file:

Step 1: Add the CXF Version

In your build.gradle, insert the following under the wsdl2java configuration:

[[See Video to Reveal this Text or Code Snippet]]

This sets the cxfVersion to 3.5.5, which should compile correctly with Java 8.

Why This Works

By forcing Gradle to use an older version of Apache CXF, you steer clear of the compatibility pitfalls that arise with newer releases that require a higher Java version. The specified version still supports the required functionalities while safely operating under the Java 8 runtime environment.

Conclusion

Working with Gradle's wsdl2java plugin can be challenging when faced with Java version conflicts and migration issues. By following the above steps to specify a compatible version of Apache CXF, you can navigate these challenges more effectively. Always remember to check your project's dependencies for conflicting versions to ensure a smoother build process.

Now, you're well-equipped to tackle the issues with the wsdl2java plugin! If you have further questions or run int