Why does this cache key cause a runtime error? @Cacheable(value = "data", key = "#param.length()") when the method parameter is an Integer named 'param'.

medium📝 Debug Q7 of 15

Spring Boot - Caching

Why does this cache key cause a runtime error? @Cacheable(value = "data", key = "#param.length()") when the method parameter is an Integer named 'param'.

AInteger has no length() method, causing a method not found error

BThe key expression syntax is invalid

CThe cache name 'data' is reserved

DThe parameter name 'param' is not recognized

Step-by-Step Solution

Solution:

Step 1: Check method call on parameter type
Integer type does not have a length() method, so calling it causes an error.
Step 2: Confirm error cause
This leads to a runtime method not found exception during cache key evaluation.
Final Answer:
Integer has no length() method, causing a method not found error -> Option A
Quick Check:
Use valid methods for parameter types in SpEL keys [OK]

Quick Trick: Check parameter types before calling methods in cache keys [OK]

Common Mistakes:

Assuming syntax error instead of runtime error
Thinking cache name causes error
Ignoring parameter name correctness

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Why does this cache key cause a runtime error? @Cacheable(value = "data", key = "#param.length()") when the method parameter is an Integer named 'param'.

Step 1: Check method call on parameter type

Step 2: Confirm error cause

Final Answer:

Quick Check:

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