Source URL: https://openjdk.org/jeps/8349536
Source: Hacker News
Title: JEP Draft: Prepare to Make Final Mean Final
Feedly Summary: Comments
AI Summary and Description: Yes
Summary: The text discusses significant upcoming changes in Java regarding the mutation of final fields through deep reflection. A future release aims to enforce immutability by default, enhancing both safety and performance, while allowing developers to enable final field mutation selectively when needed.
Detailed Description:
The document reveals a critical shift in the Java programming language aimed at enhancing integrity and performance through restrictions on the mutation of final fields. The primary points include:
– **Upcoming Changes**: Future Java releases will ensure that final fields cannot be mutated using deep reflection by default. Developers will have to explicitly allow such mutations.
– **Safety and Performance**: The ability to trust that final fields remain immutable allows the Java Virtual Machine (JVM) to optimize code execution significantly. It brings critical performance boosts via techniques like constant folding.
– **Deep Reflection**: The current Java API permits deep reflection, allowing developers to bypass the immutability of final fields, which compromises both safety and performance. Deep reflection includes methods like `setAccessible` that can change final field values at runtime.
– **Warnings and Exceptions**: With future releases, attempts to mutate final fields via deep reflection will issue warnings and eventually throw errors instead of allowing these mutations.
– **Serialization Libraries**: There is a special exemption allowed for serialization libraries to continue using reflection to mutate final fields during deserialization. The document recommends the use of the `sun.reflect.ReflectionFactory` class for this purpose.
– **Developer Guidance**: Application developers are advised to enable final field mutation selectively using command-line options, emphasizing that it is the developer’s responsibility to manage the integrity of their applications.
– **Native Code and JNI**: There are concerns regarding how native code interacts with final fields through JNI, with a warning system proposed to catch any mutable actions against final fields.
– **Risks Involved**: Existing applications relying on the current behavior may face compatibility issues after the changes are enforced. There’s an assumption that developers will adapt to these new configurations.
– **Alternatives Considered**: The document discusses various alternatives to enforcing final field immutability, such as relying on speculation by the JVM, which was deemed less practical.
The implications for security and compliance professionals are significant, as these changes might necessitate reviewing and possibly revising existing Java applications to ensure they comply with the upcoming standards and practices. This highlights the importance of maintaining due diligence in managing security controls and application integrity in line with evolving programming language specifications.