I’m working on a Java web application using docx4j to process DOCX files. I needed to add support for the namespace http://schemas.microsoft.com/office/word/2023/wordml/word16du, so I modified the org.docx4j.jaxb.NamespacePrefixMappings class in the docx4j-core-8.3.8.jar.

Additionally, the version of docx4j-core-8.3.8.jar has dependencies that are based on javax, whereas newer versions use jakarta. I find it challenging to transition the project from javax to jakarta because there are still dependencies on javax within the project.

Here are the steps I followed:

1. Decompiled the docx4j-core-8.3.8.jar using Krakatau.
2. Modified the NamespacePrefixMappings class to include the new namespace:

public class NamespacePrefixMappings {
   // Other existing code...

   public String getPreferredPrefix(String namespaceUri, String suggestion, boolean requirePrefix) {
       if (namespaceUri.equals("http://schemas.microsoft.com/office/word/2023/wordml/word16du")) {
           return "w16du";
       }
       // Existing namespace mappings...
   }

   // Other existing code...
}

3. Recompiled the class and replaced it in the docx4j-core-8.3.8.jar

After deploying the updated JAR to my Tomcat server, I encountered the following error when trying to load a DOCX file:

Caused by: java.lang.ClassNotFoundException: org.docx4j.openpackaging.packages.WordprocessingMLPackage
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1308)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1120)

Here are the steps I’ve taken to troubleshoot the issue:

1. Verified that the docx4j-core-8.3.8.jar is in the WEB-INF/lib directory.
2. Checked for duplicate versions of docx4j JAR files in WEB-INF/lib.
3. Ensured that my pom.xml includes the necessary dependencies:

This standalone application works fine, which suggests the issue might be specific to the web application deployment.

My Questions:

1. What could be causing the ClassNotFoundException for WordprocessingMLPackage in the web application but not in the standalone application?
2. Are there specific configurations or steps I might be missing when modifying the docx4j-core JAR and redeploying it in a Tomcat environment?
3. Could the issue be related to the class loader in Tomcat, and if so, how can I resolve it?
   Any guidance or suggestions would be greatly appreciated.

Environment:

• Tomcat 9
• JDK 1.8.0_292
• docx4j-core-8.3.8.jar