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Immutable Configuration Views

These utility methods in ConfigUtil create lightweight, immutable Configuration views for overrides, prefix remapping, and Properties adaptation. They support chaining and inherit scheme validation where applicable.

withOverrides

Overlay in-memory overrides on a parent Configuration:

Configuration parent = factory.getConfiguration("app");
Map<String, Object> overrides = Map.of(
    "db.host", "localhost",
    "db.port", 5432
    );
Configuration cfg = ConfigUtil.withOverrides(parent, overrides);

String host = cfg.getString("db.host"); // "localhost"
Integer port = cfg.getInteger("db.port"); // 5432 (auto-convert)
  • Overrides take precedence.
  • Lazy type conversion (null on parse fail).
  • If parent has ConfigScheme, validates overrides (throws IllegalArgumentException on mismatch).
  • getAllConfigurationKeysFlattened(): union of keys.

remapped

Remap prefixed keys for sub-config views (e.g., DB modules):

Configuration cfg = ConfigUtil.remapped(parent, "super_db.", "db.");
String host = cfg.getString("db.host"); // → parent.getString("super_db.host")
String other = cfg.getString("other.key"); // passthru
  • get("db.xxx") → parent.get("super_db.xxx").
  • Non-matching keys delegate directly.
  • Trims prefixes/keys aggressively.
  • Uniform for all typed getters; projects getAll*.
  • Inherits scheme.

fromProperties

Adapt legacy java.util.Properties:

Properties props = new Properties();
props.setProperty("key1", "value1");
props.setProperty("key2", "42");
Configuration cfg = ConfigUtil.fromProperties(props);

String v1 = cfg.getString("key1"); // "value1"
Integer v2 = cfg.getInteger("key2"); // 42 (null on fail)
  • Lazy parsing, null on errors.
  • No scheme.
  • getAllConfigurationKeysFlattened(): props keys.

Chaining

Combine freely:

Configuration dbView = ConfigUtil.withOverrides(
    ConfigUtil.remapped(parent, "legacy_db.", "db."), 
    Map.of("db.timeout", 30)
    );

Views are read-only (put* throws UnsupportedOperationException)."