What's the Best Way to Deep Copy Objects in Java?

Java: Recommended Solution for Deep Copying Objects

Deep copying instances in Java involves duplicating the entire object hierarchy, including all its mutable fields. There are several approaches to deep copying in Java:

Deep Cloning Frameworks

Third-party libraries offer robust solutions for deep cloning:

• Commons-lang SerializationUtils: Uses serialization to deep copy objects with full control over Serializable implementation.
• Java Deep Cloning Library: Leverages reflection for deep copying, providing more flexibility for cloning objects beyond your own control.

Reflection-Based Cloning

Custom reflection-based utilities or frameworks like jakarta common-beans can be employed for deep cloning:

• Pros:

  • Simple implementation
  • Low maintenance

• Cons:

  • Reduced control over cloning process
  • Potential for bugs if sub-objects are not cloned properly
  • Performance overhead due to reflection

Do-It-Yourself Approach

Manually coding a cloning method property by property ensures fine-grained control:

• Pros:

  • Tailored to specific cloning needs
  • Fast execution

• Cons:

  • Tedious and error-prone
  • Difficult to maintain

Bytecode Instrumentation

Libraries like javassit and cglib can generate custom cloners at runtime:

• Potential:

  • High performance, similar to hand-written cloners
  • Control over the cloning process

Recommendation

For deep cloning, consider using established frameworks like commons-lang SerializationUtils or the Java Deep Cloning Library for comprehensive and customizable cloning. However, if shallow cloning (duplicating only the first level of properties) is sufficient, commons-beanutils BeanUtils or Spring BeanUtils are viable options.

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