Rules

Mateu lets you define dynamic client-side behavior declaratively with @Rule.

Rules are evaluated in the browser and can modify UI state, field attributes, styles, or trigger actions.

Why this matters

A real UI is not static.

Fields may become:

• required
• disabled
• hidden

Values may change dynamically.

Styles and classes may depend on current state.

With Mateu, these behaviors can be defined declaratively in Java.

The annotation

@Repeatable(Rules.class)
@Retention(RetentionPolicy.RUNTIME)
public @interface Rule {

  String filter();

  RuleAction action();

  String fieldName();

  RuleFieldAttribute fieldAttribute();

  String value();

  String expression();

  String actionId();

  RuleResult result();
}

Actions

public enum RuleAction {
  SetAppDataValue,
  SetAppStateValue,
  SetDataValue,
  RunAction,
  RunJS,
  SetAttributeValue,
  SetStateValue,
  SetCssClass,
  SetStyle
}

Field attributes

public enum RuleFieldAttribute {
  required,
  disabled,
  hidden,
  pattern,
  minValue,
  maxValue,
  minLength,
  maxLength,
  css,
  style,
  theme,
  errorMessage,
  description,
  none
}

Result flow

public enum RuleResult {
  Continue,
  Stop
}

Mental model

Use rules to define dynamic UI behavior in the browser.

For example:

• hide a field
• make a field required
• update values
• set styles
• trigger actions

Why this fits Mateu

Rules extend the declarative model:

• fields → state
• actions → behavior
• triggers → reactions
• rules → dynamic UI behavior