WHat is the use of @Valid when @NonNull does the job for us?-CodePudding

Code in controller -

@PostMapping("/employees")
    public Employee saveEmployee(@Valid @RequestBody Employee employee) {
        return employeeService.saveEmployee(employee);
    }

Entity Object -

@NotNull(message = "Department must not be null")
@Column(name = "department")
private String department;

Suppose I pass an item with a null department field. @NonNull will throw an exception in that case. But I have seen @Valid being used for the same purpose. Can somebody elaborate why @Valid needs to be used in addition to @NonNull?

CodePudding user response：

If you omit the @Valid Spring will omit the validation on the web layer. Which basically means your controller, will not trigger validation. Validation is done by the RequestMappingHandlerAdapter when an @Valid(adted) annotation is found on an @ModelAttribute or @RequestBody annotated method argument.

JPA will also use a configured validator and trigger validation as well. So a validation exception will be thrown upon writing into the database. You can disable this with spring.jpa.properties.javax.persistence.validation.mode=none in your application.properties (or the YAML equivalent). When disabling both no validation will be done. In that case you only hope is a database constraint that the column isn't allowed to be null.

So validation is still done but the location where the validation is done is different. Due to the difference you will also get a different exception.

You have to wonder do you really want to do this somewhere upon persisting the entity with the risk of having executed some complex/time consuming business logic, or quickly upon submission of the form.

CodePudding user response：

So that the object can be validated in the Controller layer you need @Valid (or @Validated) to trigger its validation.

You can read more about this on the following online resources:

On which you can read:

Of course, the most relevant part is the use of the @Valid annotation. When Spring Boot finds an argument annotated with @Valid, it automatically bootstraps the default JSR 380 implementation — Hibernate Validator — and validates the argument.