Validation Annotations

@Validation

@Validation is repeatable (via @Validations). It defines a cross-field validation rule on a class. The condition expression is evaluated after all fields are set; if it returns true the validation fails and the error message is shown on fieldId.

@Repeatable(Validations.class)
@Retention(RetentionPolicy.RUNTIME)
public @interface Validation {
    String condition();   // expression that returns true when validation FAILS
    String fieldId();     // field to mark as invalid
    String message();     // error message to display
}

Attribute	Type	Description
`condition`	`String`	SpEL or JS expression evaluated against the form data. Returns `true` to indicate a validation failure.
`fieldId`	`String`	The field that will show the error message when the condition is met.
`message`	`String`	Human-readable error message shown next to the field.

Usage

@Validation(
    condition = "endDate != null && startDate != null && endDate < startDate",
    fieldId   = "endDate",
    message   = "End date must be on or after start date"
)
public class DateRangeForm {
    LocalDate startDate;
    LocalDate endDate;
}

Multiple validations are stacked on the same class:

@Validation(condition = "endDate != null && startDate != null && endDate < startDate",
            fieldId = "endDate", message = "End date must be on or after start date")
@Validation(condition = "amount != null && amount <= 0",
            fieldId = "amount", message = "Amount must be positive")
public class BookingForm {
    LocalDate startDate;
    LocalDate endDate;
    double amount;
}

@Validations

Container annotation for multiple @Validation entries on the same class. Created automatically by the compiler when you stack @Validation — you rarely use it directly.

@Retention(RetentionPolicy.RUNTIME)
public @interface Validations {
    Validation[] value();
}

@Rule

@Rule is repeatable (via @Rules). It defines a conditional UI rule that runs entirely on the client side: when filter matches, the specified action is applied to a field’s attribute — visibility, value, CSS class, and more — without a server round-trip.

@Repeatable(Rules.class)
@Retention(RetentionPolicy.RUNTIME)
public @interface Rule {
    String filter();                      // condition expression that activates this rule
    RuleAction action();                  // what to do when filter matches
    String fieldName();                   // target field
    RuleFieldAttribute fieldAttribute();  // which attribute to modify
    String value();                       // static value to set
    String expression();                  // dynamic expression to evaluate
    String actionId();                    // action to trigger (for RunAction)
    RuleResult result();                  // Continue or Stop processing further rules
}

Attribute	Type	Description
`filter`	`String`	Condition expression. Rule activates when this evaluates to `true`.
`action`	`RuleAction`	What to do: set a value, run an action, change appearance, etc.
`fieldName`	`String`	The field to target.
`fieldAttribute`	`RuleFieldAttribute`	Which attribute of the field to change.
`value`	`String`	Static value to assign to the attribute.
`expression`	`String`	Dynamic expression whose result is assigned to the attribute.
`actionId`	`String`	Name of the action to invoke (used with `RunAction`).
`result`	`RuleResult`	`Continue` to keep evaluating subsequent rules, `Stop` to halt.

`RuleAction` values

Value	Description
`SetDataValue`	Set a field’s data value
`SetAppDataValue`	Set a value in the application-level data store
`SetAppStateValue`	Set a value in the application-level state store
`SetAttributeValue`	Modify a field’s metadata attribute (see `RuleFieldAttribute`)
`SetStateValue`	Set a value in the component’s state
`RunAction`	Invoke a named server-side action
`RunJS`	Execute a JavaScript snippet on the client
`SetCssClass`	Add or remove a CSS class on the field
`SetStyle`	Apply inline style to the field

`RuleFieldAttribute` values

Value	Description
`required`	Whether the field is required
`disabled`	Whether the field is disabled
`hidden`	Whether the field is hidden
`pattern`	Input pattern constraint
`minValue`	Minimum numeric value
`maxValue`	Maximum numeric value
`minLength`	Minimum string length
`maxLength`	Maximum string length
`css`	CSS class(es) applied to the field
`style`	Inline style applied to the field
`theme`	Component theme variant
`errorMessage`	Custom error message
`description`	Help / description text
`none`	No attribute modification (used with `RunAction` / `RunJS`)

`RuleResult` values

Value	Description
`Continue`	Keep evaluating subsequent `@Rule` annotations after this one
`Stop`	Stop processing further rules once this one fires

@Rules

Container annotation for multiple @Rule entries on the same class. Created automatically by the compiler.

@Retention(RetentionPolicy.RUNTIME)
public @interface Rules {
    Rule[] value();
}

Combined example

A date-range booking form that cross-validates dates with @Validation and hides the discount field unless the booking is marked as corporate with @Rule:

@Validation(
    condition = "endDate != null && startDate != null && endDate < startDate",
    fieldId   = "endDate",
    message   = "End date must be on or after start date"
)
@Rule(
    filter         = "corporate == true",
    action         = RuleAction.SetAttributeValue,
    fieldName      = "discountCode",
    fieldAttribute = RuleFieldAttribute.hidden,
    value          = "false",
    expression     = "",
    actionId       = "",
    result         = RuleResult.Continue
)
@Rule(
    filter         = "corporate == false || corporate == null",
    action         = RuleAction.SetAttributeValue,
    fieldName      = "discountCode",
    fieldAttribute = RuleFieldAttribute.hidden,
    value          = "true",
    expression     = "",
    actionId       = "",
    result         = RuleResult.Continue
)
public class BookingForm {
    @NotNull
    LocalDate startDate;

    @NotNull
    LocalDate endDate;

    boolean corporate;

    String discountCode;  // only visible for corporate bookings
}