* If you didn't use FastAPI and used Starlette directly (or another tool, like Sanic, Flask, Responder, etc) you would have to implement all the data validation and serialization yourself. So, your final application would still have...

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import org.codelibs.core.lang.StringUtil;

import jakarta.validation.Constraint;
import jakarta.validation.Payload;

/**
 * Validation constraint for custom size limits based on configuration keys.
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented

 */
package org.codelibs.fess.validation;

import org.lastaflute.core.message.UserMessages;
import org.lastaflute.core.message.supplier.UserMessagesCreator;
import org.lastaflute.web.servlet.request.RequestManager;
import org.lastaflute.web.validation.ActionValidator;

/**
 * Fess-specific action validator that extends the LastaFlute ActionValidator.
 * This validator provides validation functionality for Fess web actions with custom

    /**
     * Denotes validation as performed by Maven 3.0. This validation level is meant for existing projects.
     */
    int VALIDATION_LEVEL_MAVEN_3_0 = 30;

    /**
     * Denotes validation as performed by Maven 3.1. This validation level is meant for new projects.
     */
    int VALIDATION_LEVEL_MAVEN_3_1 = 31;

    /**
     * Denotes strict validation as recommended by the current Maven version.
     */

 * governing permissions and limitations under the License.
 */
package org.codelibs.fess.validation;

import org.codelibs.fess.unit.UnitFessTestCase;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInfo;

import jakarta.validation.ConstraintValidatorContext;

public class CronExpressionValidatorTest extends UnitFessTestCase {

}(this,function(a){!function(a){"use strict";a.formUtils.registerLoadedModule("jsconf"),a.setupValidation=function(b){var c=a(b.form||"form");a.each(b.validate||b.validation||{},function(b,d){var e;e="#"===b[0]?a(b):"."===b[0]?c.find(b):c.find('*[name="'+b+'"]'),e.attr("data-validation",d.validation),a.each(d,function(a,b){"validation"!==a&&b!==!1&&(b===!0&&(b="true"),"_"===a[0]?(a=a.substring(1),b===!1?e.removeAttr(a):e.attr(a,b)):e.valAttr(a,b))})}),a.validate(b)}}(a)});...

 */
package org.codelibs.fess.validation;

import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Set;

import org.codelibs.fess.unit.UnitFessTestCase;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInfo;

import jakarta.validation.ConstraintViolation;
import jakarta.validation.Validation;
import jakarta.validation.Validator;

 * governing permissions and limitations under the License.
 */
package org.codelibs.fess.validation;

import java.lang.annotation.Annotation;

import org.codelibs.fess.unit.UnitFessTestCase;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInfo;

import jakarta.validation.ConstraintValidatorContext;
import jakarta.validation.Payload;

public class CustomSizeValidatorTest extends UnitFessTestCase {

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

   ** file model validation: <<<ModelValidator>>> ({{{./apidocs/org/apache/maven/model/validation/ModelValidator.html}javadoc}}),
   with its <<<DefaultModelValidator>>> implementation
   ({{{./xref/org/apache/maven/model/validation/DefaultModelValidator.html}source}})

   []

 * phase 2, with optional plugin processing