"content": {"application/json": {"schema": {}}},
                            },
                            "422": {
                                "description": "Validation Error",
                                "content": {
                                    "application/json": {
                                        "schema": {

import org.lastaflute.web.validation.ActionValidator;
import org.lastaflute.web.validation.LaValidatable;
import org.lastaflute.web.validation.VaMessenger;

import jakarta.annotation.Resource;

/**
 * The base action class for Fess web application.
 * This abstract class provides common functionality for all Fess web actions,
 * including user authentication, validation, message handling, and access context management.

     */
    protected abstract void processRequest(Client client, Deferred<T> deferred);

    /**
     * Returns a validation error message, or null if there are no errors.
     * @return A validation error message, or null.
     */
    protected abstract String getValidationError();

if [ -n "${distributionSha256Sum-}" ]; then
  distributionSha256Result=false
  if [ "$MVN_CMD" = mvnd.sh ]; then
    echo "Checksum validation is not supported for maven-mvnd." >&2
    echo "Please disable validation by removing 'distributionSha256Sum' from your maven-wrapper.properties." >&2
    exit 1
  elif command -v sha256sum >/dev/null; then

    dependentRequired: dict[str, set[str]] | None = None
    # Ref: JSON Schema Validation 2020-12: https://json-schema.org/draft/2020-12/json-schema-validation.html#name-vocabularies-for-semantic-c
    # Vocabularies for Semantic Content With "format"
    format: str | None = None
    # Ref: JSON Schema Validation 2020-12: https://json-schema.org/draft/2020-12/json-schema-validation.html#name-a-vocabulary-for-the-conten

d=!0,!1}),d},f=function(){var b=a(this),d=a.formUtils.getValue(b),e=b.valAttr("depending-value");a.each(this.dependingInputs,function(b,f){var g=!!a.formUtils.getValue(f),h=!d||e&&e!==d;h&&!g&&a.formUtils.dialogs.removeInputStylingAndMessage(f,c)})};b.find("[data-validation-depends-on]").off("beforeValidation",d).on("beforeValidation",d).each(function(){var c=a(this);b.find('[name="'+c.valAttr("depends-on")+'"]').each(function(){a(this).off("change",f).on("change",f).valAttr("depending-value",c.valAttr("depends-on...

                                        .success("%sConfiguration validation of %s: %s")
                                        .build()
                                : messageBuilderFactory
                                        .builder()
                                        .failure("%sConfiguration validation of %s: %s")
                                        .build(),
                        indent,

                                    }
                                },
                            },
                            "422": {
                                "description": "Validation Error",
                                "content": {
                                    "application/json": {
                                        "schema": {

                                    "content": {"application/json": {"schema": {}}},
                                },
                                "422": {
                                    "description": "Validation Error",
                                    "content": {
                                        "application/json": {
                                            "schema": {

    }
}
```

Again, doing just that declaration, with **FastAPI** you get:

* Editor support (completion, etc.), even for nested models
* Data conversion
* Data validation
* Automatic documentation

## Special types and validation { #special-types-and-validation }

Apart from normal singular types like `str`, `int`, `float`, etc. you can use more complex singular types that inherit from `str`.