Getting Started

This section will guide you through the setup and basic usage of ModelMapper.

Setting Up

If you’re a Maven user just add the modelmapper library as a dependency:

<dependency>
  <groupId>org.modelmapper</groupId>
  <artifactId>modelmapper</artifactId>
  <version>0.7.2</version>
</dependency>

Otherwise you can download the latest ModelMapper jar and add it to your classpath.

Mapping

Let’s try mapping some objects. Consider the following source and destination object models:

Source model

// Assume getters and setters on each class
class Order {
  Customer customer;
  Address billingAddress;
}

class Customer {
  Name name;
}

class Name {
  String firstName;
  String lastName;
}

class Address {
  String street;
  String city;
}

Destination Model

// Assume getters and setters
class OrderDTO {
  String customerFirstName;
  String customerLastName;
  String billingStreet;
  String billingCity;
}

We can use ModelMapper to implicitly map an order instance to a new OrderDTO:

ModelMapper modelMapper = new ModelMapper();
OrderDTO orderDTO = modelMapper.map(order, OrderDTO.class);

And we can test that properties are mapped as expected:

assertEquals(order.getCustomer().getName().getFirstName(), orderDTO.getCustomerFirstName());
assertEquals(order.getCustomer().getName().getLastName(), orderDTO.getCustomerLastName());
assertEquals(order.getBillingAddress().getStreet(), orderDTO.getBillingStreet());
assertEquals(order.getBillingAddress().getCity(), orderDTO.getBillingCity());

How It Works

When the map method is called, the source and destination types are analyzed to determine which properties implicitly match according to a matching strategy and other configuration. Data is then mapped according to these matches.

Even when the source and destination objects and their properties are different, as in the example above, ModelMapper will do its best to determine reasonable matches between properties according to the configured matching strategy.

Explicit Mapping

While ModelMapper will do its best to implicitly match source and destination properties for you, sometimes you may need to explicitly define mappings between properties.

ModelMapper supports a variety of mapping approaches, allowing you to use any mix of methods and field references. Let’s map Order.billingAddress.street to OrderDTO.billingStreet and map Order.billingAddress.city to OrderDTO.billingCity. First we’ll define a PropertyMap that contains these mappings:

PropertyMap<Order, OrderDTO> orderMap = new PropertyMap<Order, OrderDTO>() {
  protected void configure() {
    map().setBillingStreet(source.getBillingAddress().getStreet());
    map(source.billingAddress.getCity(), destination.billingCity);
  }
};

Then with our mappings defined we can add them to our ModelMapper instance:

modelMapper.addMappings(orderMap);

Conventional Configuration

As an alternative to manually mapping Order.billingAddress.street to OrderDTO.billingStreet, we can configure different conventions to be used when ModelMapper attempts to match these properties. The Loose matching strategy, which more loosely matches property names, will work in this case:

modelMapper.getConfiguration().setMatchingStrategy(MatchingStrategies.LOOSE);

Additional matching strategies and other conventions can also be configured to control ModelMapper’s property matching process.

Validating Matches

Aside from writing tests to verify that your objects are being mapped as expected, ModelMapper has built-in validation that will let you know if any destination properties are unmatched.

First we have to let ModelMapper know about the types we want to validate. We can do this by creating a TypeMap:

modelMapper.createTypeMap(Order.class, OrderDTO.class);

Or we can add mappings from a PropertyMap which will automatically create a TypeMap if one doesn’t already exist for the source and destination types:

modelMapper.addMappings(new OrderMap());

Then we can validate our mappings:

modelMapper.validate();

If any TypeMap contains a destination property that is unmatched to a source property a ValidationException will be thrown.

Next Steps

Congratulations! You’ve learned how to map objects with safety and ease.

There’s a lot more to ModelMapper, including the complete mapping API and configuration options. Check out the user manual to learn more. You can also check out some additional examples of ModelMapper in action.