Converters

Conversion to a destination type or property can be delegated to a Converter. Converters generally take the place of any implicit or explicit mappings between two types (see below for exceptions).

Creating a Converter

Converters can be implemented in two ways. The first is by extending AbstractConverter:

Converter<String, String> toUppercase = new AbstractConverter<String, String>() {
  protected String convert(String source) {
    return source == null ? null : source.toUppercase();
  }
};

The second way is by implementing the Converter interface which exposes a MappingContext that contains contains information related to the current mapping request:

Converter<String, String> toUppercase = new Converter<String, String>() {
  public String convert(MappingContext<String, String> context) {
    return context.getSource() == null ? null : context.getSource().toUppercase();
  }
};

Configuration

Converters can be configured for use in several ways. The first is by adding the converter to a ModelMapper:

modelMapper.addConverter(personConverter);

This, in turn, sets the converter against the TypeMap corresponding to the source and destination types Person and PersonDTO.

A Converter can also be set directly against a TypeMap:

personTypeMap.setConverter(personConverter);

We can also specify a Converter to be used when converting properties within a TypeMap:

personTypeMap.setPropertyConverter(propertyConverter);

Converters can also be set for specific properties. See the mapping API page on converters for more info using converters with properties.

Conversion with Mapping

While Converters by default take the place of any mappings between two types, they can also be used in addition to any defined mappings.

personTypeMap.setPreConverter(personConverter);

This specifies that the personConverter should be run before, and in addition to, the defined mappings for the personTypeMap. We can also specify that the personConverter be used after, and in addition to, the defined mappings:

personTypeMap.setPostConverter(personConverter);