Java Platform Module System (JPMS) provides a modular structure for Java applications, allowing developers to organize their code more efficiently. While there are numerous positive aspects of using JPMS modules, it is crucial to also consider the potential negative benefits that may arise.

Increased Complexity

Implementing JPMS modules introduces additional complexity, especially for library developers who need to ensure compatibility with a wide range of Java applications. The creation of module descriptors and the management of module dependencies can be intricate and time-consuming. Developers must carefully align their libraries with the specific requirements and constraints of the target application, making the development process more challenging.

Example: A library developer needs to create a module descriptor for their library, specifying its dependencies and exports. Inconsistent or conflicting module descriptors may lead to unexpected behavior or compatibility issues.

Compatibility Issues

With the introduction of JPMS modules, compatibility issues may arise when libraries developed without module descriptors are used within a modular application. Such libraries, referred to as "Automatic Modules," lack explicit module declarations and therefore may not adhere to the strict module boundaries enforced by JPMS. This can result in runtime errors or unexpected behavior.

Example: A library developer has a well-established library used in various applications. When a modular application using JPMS tries to include this library as an automatic module, it may encounter unresolved dependencies or conflicting module boundaries, leading to compatibility issues.

Fragmented Ecosystem

The adoption of JPMS modules by Java developers has been gradual, leading to a fragmented ecosystem where some libraries embrace modules while others still rely on the traditional classpath approach. Library developers may need to support multiple deployment scenarios to cater to different applications, increasing maintenance efforts and creating a fragmented landscape for developers and users alike.

Example: A library developer needs to provide two different distribution packages, one compatible with modular applications and another for traditional classpath-based applications. This dual support adds complexity to the release process and increases the chances of inconsistencies between module and classpath versions.

Increased Learning Curve for Developers

Transitioning from the traditional classpath model to JPMS modules requires library developers to acquire new knowledge and skills. Developers may need to understand the intricacies of module descriptors, adapt their development workflows, and learn best practices for managing module dependencies. This learning curve can be time-consuming and may slow down the development process initially.

Example: A seasoned library developer has to invest time and effort in understanding the intricacies of JPMS modules, including concepts like module paths, modular encapsulation, and qualified exports. This learning process can temporarily slow down their development pace until they become proficient in working with modules.

While JPMS modules offer numerous benefits for Java developers, it is essential to acknowledge the potential negative aspects that library developers may encounter. Increased complexity, compatibility issues, a fragmented ecosystem, and a learning curve are among the challenges associated with implementing JPMS modules in libraries. By carefully addressing these issues, library developers can leverage the positive aspects of JPMS modules to create more robust and modular libraries that facilitate the development of scalable and maintainable Java applications.