Micronaut Validation documentation incorrect statement about @Introspected

[sergey-morenets]

Expected Behavior

Validation documentation shouldn't state that @Introspected annotation is required for validation.

Actual Behaviour

Current Micronaut Validation documentation (https://micronaut-projects.github.io/micronaut-validation/snapshot/guide/) states that:

To validate data classes, e.g. POJOs (typically used in JSON interchange), the class must be annotated with @Introspected (see Micronaut Guide Introspection section) or, if the class is external, be imported by the @Introspected annotation.

However that's not true as per Micronaut 4.1.4.

So here's our POJO:

public class Product {

    @NotEmpty
    private String name;

    private int id;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
}

And our configuration class:

@SerdeImport(Product.class)
public class BeanValidationConfiguration {
}

So there's no @Introspected here (@SerdeImport is meta-annotation but doesn't contain it) however Jakarta Validation works which was confirmed by our tests.

Steps To Reproduce

No response

Environment Information

No response

Example Application

No response

Version

4.1.4

[nedelva]

Suppose we generate a Micronaut application (Java 17+Maven) with the following features: validation, serialization-jackson, lombok, http-client, then add these classes:

package org.acme.model;

import jakarta.validation.constraints.NotEmpty;
import lombok.Data;

@Data
public class Product {
    @NotEmpty
    private String name;

    private int id;
}

We add also a validated controller:

package org.acme;

import io.micronaut.http.annotation.Body;
import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Post;
import jakarta.validation.Valid;
import org.acme.model.Product;

@Controller("/product")
public class ProductsController {
    @Post
    public String addProduct(@Valid @Body Product product) {
        return String.format("added product %s", product);
    }
}

Start the application with mn:run and issue a POST request in your favorite http client app:

POST http://localhost:8080/product
Content-Type: application/json

{
  "id": 1000, "name": null
}

I have a few remarks:

1. Without the BeanValidationConfiguration class annotated with @SerdeImport there will be an error stating

   " No bean introspection available for type [class org.acme.model.Product]. Ensure the class is annotated with io.micronaut.core.annotation.Introspected""

So fixing the error should be straightforward: annotate the class with @Introspected. Problem is, this time around we get another error:

"Internal Server Error: No deserializable introspection present for type: Product product. Consider adding Serdeable.Deserializable annotate to type Product product. Alternatively if you are not in control of the project's source code, you can use @SerdeImport(Product.class) to enable deserialization of this type."

When we use the annotation Serdeable.Deserializable we get the expected output:

{
  "_links": {
    "self": [
      {
        "href": "/product",
        "templated": false
      }
    ]
  },
  "_embedded": {
    "errors": [
      {
        "message": "product.name: must not be empty"
      }
    ]
  },
  "message": "Bad Request"
}

2. The last error suggested an alternative to Serdeable.Deserializable, which brings me to the second point, using the @SerdeImport(Product.class) annotation. This is what OP tried and I can confirm that if you use it, no extra annotations are required on Product. This should come as unsurprising though, because the intented usage of @SerdeImport is to introspect external classes (from a library that you do not own @sergey-morenets).

Conclusion

The section 5 of Validation docs is indeed incorrect with respect to point 1 (it should have mentioned @Serdeable.Deserializable instead of @Introspected) and incomplete with respect to point 2 (a quick remark could be added there, that you don't need @Introspected on your own classes if you choose to mark them via @SerdeImport.)