Play framework -使表单验证异步-编译错误

import play.data.Form;
import play.data.validation.Constraints;
import play.mvc.Controller;
import play.mvc.Result;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;

public class UserController extends Controller {

    public CompletionStage<Result> submitForm() {
        Form<UserForm> userForm = Form.form(UserForm.class).bindFromRequest();

        if (userForm.hasErrors()) {
            return CompletableFuture.completedFuture(badRequest(userForm.errorsAsJson()));
        } else {
            UserForm formData = userForm.get();
            // 处理表单数据
            return CompletableFuture.completedFuture(ok("Form submitted successfully"));
        }
    }

    public CompletionStage<Result> validateForm() {
        Form<UserForm> userForm = Form.form(UserForm.class).bindFromRequest();

        if (userForm.hasErrors()) {
            return CompletableFuture.completedFuture(badRequest(userForm.errorsAsJson()));
        } else {
            UserForm formData = userForm.get();
            // 执行异步验证
            return validateAsync(formData).thenApplyAsync(validationResult -> {
                if (validationResult.isValid()) {
                    // 验证成功
                    return ok("Form validated successfully");
                } else {
                    // 验证失败
                    return badRequest(validationResult.errorsAsJson());
                }
            });
        }
    }

    private CompletionStage<ValidationResult> validateAsync(UserForm formData) {
        // 异步验证逻辑
        return CompletableFuture.supplyAsync(() -> {
            // 执行验证逻辑
            // 返回验证结果
            return new ValidationResult(true);
        });
    }

    public static class UserForm {
        @Constraints.Required
        public String username;

        @Constraints.Required
        public String password;
    }

    public static class ValidationResult {
        private boolean valid;

        public ValidationResult(boolean valid) {
            this.valid = valid;
        }

        public boolean isValid() {
            return valid;
        }

        public Object errorsAsJson() {
            // 返回错误信息
            return null;
        }
    }
}