🧩 Your MapStruct Mappers Are Hiding Null Bugs

Short summary

MapStruct mappers silently hide null bugs by default because unmappedTargetPolicy is WARN, which gets ignored in build logs—a production incident waiting to happen. Set unmappedTargetPolicy to ERROR to force the compiler to catch missing field mappings before code ships. Three configuration practices—ERROR reporting, Spring component model, and safe mapping patterns—eliminate silent nulls and reduce boilerplate.

• •MapStruct's default WARN policy silently skips unmapped fields, causing production nulls weeks after deployment
• •Change unmappedTargetPolicy to ERROR to move mapping validation from runtime to compile time
• •Use Spring injection in production, Mappers.getMapper() in unit tests, and MapStruct-generated code to eliminate hand-written mapping loops and switch statements

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