Message Resolution

The MessageResolver loads messages from Java ResourceBundle files (.properties) and supports locale-aware message lookup. This is essential for internationalized validation error messages and user-facing text.

Properties File

Define your messages in a standard Java properties file (e.g., messages.properties):

# messages.properties
error.name.required=Name is required
error.email.invalid=Email address is invalid
error.age.minimum=Age must be at least {0}
warning.deprecated=This feature is deprecated

Creating a MessageResolver

// Create a resolver from a resource bundle
MessageResolver resolver = MessageResolver.builder("messages").build();

// Look up a message
String msg = resolver.resolve(Locale.getDefault(), "error.name.required");
// "Name is required"

// With a default fallback
String msg2 = resolver.resolve(Locale.getDefault(), "unknown.key", "Default text");
// "Default text"

Multiple Bundles

You can register multiple resource bundles. The resolver searches them in order until it finds a match:

MessageResolver resolver = MessageResolver.builder(
    "messages", "validation_messages").build();
// Searches both bundles in order

Integration with RuleContext

Wire your message resolver into the RuleContext so validation rules can automatically resolve messages:

RuleContext ctx = RuleContext.builder()
    .messageResolver("messages")
    .build(bindings);

Locale Support

Java ResourceBundles support locale-specific files using the standard naming convention. The resolver will automatically pick the correct file based on the active locale:

Use Case

Message resolution is primarily used for internationalized validation error messages. By externalizing messages into properties files, you can support multiple languages without changing your rule logic, and maintain a single source of truth for all user-facing text.