Every data transformation you'll ever write falls into one of six patterns:
- Leaf - One thing. No substeps. Atomic.
- Sequencer - This, then that. Output becomes input.
- Fork-Join - These together, then combine. Independent operations merging.
- Condition - Which path? Route based on value.
- Iteration - Same thing, many times. Transform a collection.
- Aspects - Wrap it. Add retry, timeout, logging around an operation.
That's it. Not "covers most cases." Everything.
Why Only Six?
These aren't design patterns someone invented. They're the fundamental ways data can flow:
1. Transform a value (Leaf)
2. Chain dependent transforms (Sequencer)
3. Combine independent transforms (Fork-Join)
4. Choose between transforms (Condition)
5. Apply transform to many values (Iteration)
6. Enhance a transform (Aspects)
There's no seventh option. Data either transforms, chains, combines, branches, iterates, or gets wrapped.
The Strange Coincidence
These same six patterns describe every business process:
- Leaf: "Validate the email format"
- Sequencer: "First verify identity, then check permissions, then grant access"
- Fork-Join: "Get profile, balance, and transactions, then build dashboard"
- Condition: "If premium user, apply discount"
- Iteration: "For each cart item, calculate tax"
- Aspects: "Log every payment attempt"
This isn't coincidence. Business logic IS data transformation - we just use different words.
The Translation
- "First... then..." -> Sequencer -> .flatMap() chain
- "Get X and Y and Z, then..." -> Fork-Join -> Promise.all()
- "If... otherwise..." -> Condition -> Ternary/switch
- "For each..." -> Iteration -> .map()
- "Always log/retry..." -> Aspects -> Wrapper
No impedance mismatch. Same six concepts, different vocabulary.
Gap Detection
When you model business processes using these patterns, gaps become visible.
Missing validation: Building a Sequencer but nothing validates input before step one? Gap found.
Unclear dependencies: Business describes five things. Sequencer or Fork-Join? If they can't tell you which outputs feed which inputs, the process isn't defined.
Inefficient flows: Business describes sequential A, B, C, then combine. But if A, B, C don't depend on each other, this should be Fork-Join. Pattern reveals inefficiency.
The Result
Six patterns. Complete coverage. Shared language between developers and business.
The irony? You'll spend an hour asking the right questions. The coding takes 30 seconds.
From Java Backend Coding Technology: https://github.com/siy/coding-technology
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