Refactoring JD Express Refund, Amount Calculation, and Reverse Billing Modules: Design, Implementation, and Outcomes

Background : JD Express refund, amount calculation, and reverse‑billing modules suffered from tangled code, duplicated logic, and unclear domain boundaries, resulting in high maintenance costs and system instability.

Refactoring Approach : A combination of small‑scale and large‑scale refactoring was applied, leveraging design patterns such as abstract‑factory, strategy, and chain‑of‑responsibility. Code smells were identified, large classes were split, methods extracted, and redundant logic consolidated into unified services.

System Stability Measures : The refactor was performed in incremental steps with comprehensive test cases, gray‑release isolation, continuous monitoring, performance testing, and thorough team code reviews to ensure no regression and maintain reliability.

Results : Development and maintenance costs were reduced, code quality and system stability improved, business boundaries became clearer, extensibility increased, and developers gained deeper understanding of refactoring principles.

Code Showcase : Before‑and‑after diagrams illustrate the consolidation of multiple calculation logics into a single, pattern‑driven implementation; the core amount‑calculation method was reduced to four steps, and a chain‑of‑responsibility handles item‑ and SKU‑level calculations.