Mapper and strategies

Understand the mapper, mapping strategies, error handling, and global logger configuration.

Mapper owns registered mappings and executes map and mutation operations. Create it with one mapping strategy:

const mapper = createMapper({
  strategyInitializer: classes(),
});

Mapping strategies

A strategy discovers, retrieves, and applies model metadata. It also constructs destination objects and can preprocess source or postprocess destination values.

Package	Initializer	Metadata source
`@automapper/classes`	`classes()`	`@AutoMap()` and reflected class metadata
`@automapper/pojos`	`pojos()`	`PojosMetadataMap` registrations
`@automapper/mikro`	`mikro()`	Class metadata adapted for MikroORM entities
`@automapper/sequelize`	`sequelize()`	Class metadata adapted for Sequelize models

mikro() and sequelize() extend the classes strategy with integration-specific defaults.

Mapper lifetime

Register mappings once and reuse the mapper. Call mapper.dispose() when its mapping registry is no longer needed, such as during application or test teardown.

Error handling

Without a custom errorHandler, mapper failures are forwarded to AutoMapperLogger.error. Supply an ErrorHandler when your application needs different behavior:

const mapper = createMapper({
  strategyInitializer: classes(),
  errorHandler: {
    handle(error: unknown) {
      throw error;
    },
  },
});

Failures use AutoMapperError, MappingNotFoundError, and MapMemberError, allowing consumers to narrow mapping failures with instanceof.

Logger

AutoMapper’s default logger delegates to console with an [AutoMapper]: prefix. It supports log, info, warn, error, debug, verbose, fatal, and optional trace methods.

const restore = AutoMapperLogger.configure({
  error: (message, ...details) => appLogger.error({ message, details }),
  warn: () => undefined,
});

restore(); // restore the previously active configuration
AutoMapperLogger.reset(); // restore console-backed defaults

Configure logging as early as possible when you need to capture warnings emitted while decorators are evaluated.