How to Avoid \'Xerces Hell\' in Java/Maven?

Dealing with "Xerces Hell" in Java/Maven?

Background

Xerces, a widely used XML parser in the Java ecosystem, poses significant challenges due to historical factors and packaging issues. The official Xerces binaries lack versioning, and the project is not uploaded to Maven Central officially. Additionally, the split of Xerces into multiple jars (xml-apis, xercesImpl) and the varying versioning practices by different parties have compounded the problem. This leads to conflicts and classloader issues when using Xerces in Maven environments.

Problems

Conflict Resolution

Maven's inability to resolve conflicts between different versions of the same artifact, even when published by different organizations, leads to situations where multiple Xerces dependencies are included, potentially resulting in classpath conflicts.

Classloader Hell

The inclusion of Xerces in both the JAXP reference implementation and servlet containers, combined with the potentially conflicting versions from Maven dependencies, creates a complex classloading scenario, requiring careful management to avoid classloader conflicts at runtime.

Solutions

Attempts to exclude or mark Xerces dependencies as provided can be challenging due to the multiple aliases and dependencies of third-party libraries and frameworks. However, a significant development has emerged:

Recent Update

In February 2013, a patched version of the Xerces build scripts was uploaded to fix the Maven Central upload issue. Xerces 2.11.0 JARs are now available in Maven Central, resolving the long-standing versioning and packaging problems.

This development significantly simplifies Xerces dependency management in Maven projects. Developers can now use the following dependency declaration to resolve Xerces correctly:

<dependency>
    <groupid>xerces</groupid>
    <artifactid>xercesImpl</artifactid>
    <version>2.11.0</version>
</dependency>

This solution eliminates the need for fine-grained dependency control and complex tiered classloading mechanisms.

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