# Stop Letting Jackson Accept Garbage: Strict JSON Parsing in Spring Boot
java
dev.to
Most Spring Boot APIs think they are strict — until a client sends something slightly “off”, and your app quietly accepts it. Examples I’ve seen in real systems: "count": "10" (string) accepted where you expected an integer "amount": 1.2 accepted where you expected an integer cents value "age": "" becoming 0 or null depending on coercion rules unknown fields being ignored (and bugs staying hidden for months) If you care about contracts, lenient deserialization is technical debt. The e