You want to cache results of a method that takes two parameters: userId (Long) and filter (String). Which cache key strategy ensures unique keys for each combination?
hard📝 Application Q15 of 15
Spring Boot - Caching
You want to cache results of a method that takes two parameters: userId (Long) and filter (String). Which cache key strategy ensures unique keys for each combination?
BUse <code>key = "#userId + #filter"</code> without conversion
CUse <code>key = "#userId"</code> only
DUse <code>key = "#filter"</code> only
Step-by-Step Solution
Solution:
Step 1: Understand need for unique keys per parameter combo
Using only one parameter as key risks collisions when other parameter changes.
Step 2: Evaluate options for combining parameters
Use key = "#userId + #filter" without explicit conversion risks type issues. Use key = "T(java.util.Objects).hash(#userId, #filter)" uses Java's Objects.hash to combine both safely. Using only one parameter causes collisions.
Final Answer:
Use key = "T(java.util.Objects).hash(#userId, #filter)" -> Option A
Quick Check:
Combine keys safely with Objects.hash [OK]
Quick Trick:Use Objects.hash to combine multiple parameters safely [OK]
Common Mistakes:
Concatenating keys without type safety
Using only one parameter as key causing collisions
Ignoring proper SpEL syntax for static method calls
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