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SUBSCRIBE NOWUnderstanding the Flyweight Sequence Flow
The Flyweight Design Pattern is a structural pattern focused on minimizing memory footprint by sharing common object instances. While class diagrams show static relationships, a Sequence Diagram demonstrates how messages and execution flow across objects dynamically over time.
In this workflow, the client never directly instantiates concrete flyweight objects. Instead, every request passes through a centralized factory that acts as an intelligent cache manager.
Step-by-Step Message Execution Order
- Step 1: Client Request: The
Clientsends a request to theFlyweightFactorycallinggetFlyweight(key). - Step 2: Cache Lookup: The
FlyweightFactorychecks its internal collection (such as a HashMap or pool) for the requested key. - Step 3: Conditional Creation:
- If the object exists, the factory immediately returns the cached instance.
- If the object does not exist, the factory creates a new
ConcreteFlyweight, stores it in the pool, and then returns it.
- Step 4: Operation Invocation: The
Clientreceives the flyweight instance and calls its operation method, passing any dynamic extrinsic state as method parameters.
Key Architectural Takeaways
- Encapsulated Lifecycle: The factory retains full control over when to instantiate and when to reuse shared objects.
- Context Independence: The flyweight object remains stateless regarding external variations, receiving context on-demand through operation parameters.
- Scalability: Even under high loads with millions of interactions, the total number of objects in memory stays bounded and predictable.
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| Flyweight Design pattern - Sequence Diagram |
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