How does method validation work for Spring MVC controller parameters?

Explains direct parameter constraints, object cascades, built-in MVC validation, error aggregation, and stable response handling.

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Spring MVC can validate constraints declared directly on handler parameters, such as @Min on a path variable or @NotBlank on a query parameter, as well as constraints on return values. When method validation applies, it covers the method parameters and nested object constraints reached through @Valid. Modern MVC reports these failures through HandlerMethodValidationException. This differs from validating only one request object during argument resolution.

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Modern handler-method validation, distinction from body-object validation, parameter locations, and error mapping.

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A constraint on a handler parameter changes validation from one bound object to the complete method invocation.
Spring MVC can validate constraints declared directly on handler parameters, such as @Min on a path variable or @NotBlank on a query parameter, as well as constraints on return values. When method validation applies, it covers the method parameters and nested object constraints reached through @Valid. Modern MVC reports these failures through HandlerMethodValidationException. This differs from validating only one request object during argument resolution.
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Assuming request-body validation covers every method parameter.
Returning raw parameter names as a permanent contract accidentally.
Mixing local BindingResult handling with unrelated global failures.

How does method validation work for Spring MVC controller parameters?

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