how to parse a complex, densely nested object graph into a more straightforward model for use in another domain.

To parse a complex, densely nested object graph into a more straightforward model for use in another domain, you can use a technique called "object mapping" or "object transformation". This involves mapping the complex object graph to a simpler model that is more appropriate for the other domain.

Here are the general steps for object mapping:

1. Define the target model: Define the simpler model that you want to map to. This model should have only the properties that are relevant to the other domain.

2. Define the mapping rules: Define the rules for mapping the properties from the complex object graph to the properties in the target model. This may involve combining or filtering properties, renaming properties, or converting data types.

3. Implement the mapping: Implement the mapping rules using a mapping library or manually. One popular mapping library for Java is MapStruct, but there are many others available.

Here's an example of object mapping using MapStruct:

Suppose you have a complex object graph representing a library with many books, authors, and publishers. You want to map this to a simpler model that only includes the title, author name, and publisher name for each book.

1. Define the target model:

public class BookInfo {
    private String title;
    private String authorName;
    private String publisherName;
    // getters and setters
}

2. Define the mapping rules:

@Mapper
public interface LibraryMapper {

    @Mapping(source = "book.title", target = "title")
    @Mapping(source = "book.author.name", target = "authorName")
    @Mapping(source = "book.publisher.name", target = "publisherName")
    BookInfo mapBookToBookInfo(Book book);
}

3. Implement the mapping:

LibraryMapper mapper = Mappers.getMapper(LibraryMapper.class);
List<BookInfo> bookInfos = library.getBooks().stream()
    .map(mapper::mapBookToBookInfo)
    .collect(Collectors.toList());

This will map the complex object graph to a simpler model that is more appropriate for use in another domain.