configuration

name	configuration
description	Type-safe validated configuration properties from application.yml. Use when adding any externalisable value.

Skill: Configuration

When to load it: When adding any new configurable value or environment-specific behaviour to a feature.

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What This Skill Does

Produces type-safe, validated configuration properties bound from application.yml. Enforces fail-fast validation at startup and keeps configurable values out of Java source.

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Rules

1. All configurable values go in application.yml. Never hardcoded in Java source.
2. Group related properties under a @ConfigurationProperties class. Do not use @Value for more than one related property.
3. Validate at startup with @Validated. Fail fast — a misconfiguration discovered at runtime is worse than a failed startup.
4. Provide sensible defaults for non-critical values. Do not require configuration for things with an obvious default.
5. Document each property in application.yml with a comment.

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Pattern

@ConfigurationProperties(prefix = "[feature]")
@Validated
public record [Feature]Properties(
    @NotBlank String [requiredProperty],
    @Min(1) @Max(100) int [boundedProperty],
    @Positive double [positiveProperty]
) {}

# application.yml
[feature]:
  # [What this property controls. Required.]
  [required-property]: [value]
  # [What this property controls. Range: 1–100. Default: 10.]
  [bounded-property]: 10
  # [What this property controls. Must be positive.]
  [positive-property]: 0.7

Register in Spring Boot:

@Configuration
@EnableConfigurationProperties([Feature]Properties.class)
public class [Feature]Config {}

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Design Constraints

• Do not hardcode configurable values in Java source — always application.yml
• Do not use @Value when two or more related properties exist — use @ConfigurationProperties
• Do not skip @Validated — startup validation is not optional
• Do not provide a default for required values — required means no default