How can you connect a new data object (DTO) that cannot be changed with an existing DTO?

If a new DTO is immutable, and you need to associate it with an existing DTO, the pattern of transformation or adaptation is usually used. This can be done through a constructor or a static method that takes the existing DTO and creates a new object based on it.

Example in Java:

public final class NewDTO {
    private final String field1;
    private final int field2;

    public NewDTO(OldDTO oldDto) {
        this.field1 = oldDto.getField1();
        this.field2 = oldDto.getField2();
    }

    // getters without setters
}

Thus, you create a new object that contains data from the old DTO, while ensuring the immutability of the new object. You can also use mapping libraries, such as MapStruct, to automate the transformation between DTOs.