タイプ コーデックによるデータのエンコード

CodecRegistry codecRegistry = CodecRegistries.fromCodecs(new IntegerCodec(), new ReadStatusCodec());

Codec<ReadStatus> readStatusCodec = codecRegistry.get(ReadStatus.class);
Codec<Integer> integerCodec = codecRegistry.get(Integer.class);

public class BookCodecProvider implements CodecProvider {
    public BookCodecProvider() {}
    @Override
    @SuppressWarnings("unchecked")
    public <T> Codec<T> get(Class<T> clazz, CodecRegistry registry) {
        if (clazz == Book.class) {
            return (Codec<T>) new BookCodec(registry);
        }
        // return null when not a provider for the requested class
        return null;
    }
}

BsonTypeClassMap bsonTypeClassMap = new BsonTypeClassMap();
Class<?> clazz = bsonTypeClassMap.get(BsonType.ARRAY);
System.out.println("Java type: " + clazz.getName());

Map<BsonType, Class<?>> replacements = new HashMap<BsonType, Class<?>>();
replacements.put(BsonType.ARRAY, Set.class);
BsonTypeClassMap bsonTypeClassMap = new BsonTypeClassMap(replacements);
Class<?> clazz = bsonTypeClassMap.get(BsonType.ARRAY);
System.out.println("Java type: " + clazz.getName());

public class Book {
    private String title;
    private ReadStatus readStatus = ReadStatus.UNREAD;
    private Integer pageCount;
    public Book() {}
    // ...

public class BookCodec implements Codec<Book> {
    private Codec<String> stringCodec;
    private Codec<ReadStatus> readStatusCodec;
    private Codec<Integer> integerCodec;
    public BookCodec(CodecRegistry registry) {
        this.stringCodec = registry.get(String.class);
        this.readStatusCodec = registry.get(ReadStatus.class);
        this.integerCodec = registry.get(Integer.class);
    }
    // Defines an encode() method to convert Book field values to BSON values
    @Override
    public void encode(BsonWriter writer, Book value, EncoderContext encoderContext) {
        writer.writeStartDocument();
        writer.writeName("title");
        stringCodec.encode(writer, value.getTitle(), encoderContext);
        writer.writeName("readStatus");
        readStatusCodec.encode(writer, value.getReadStatus(), encoderContext);
        writer.writeName("pageCount");
        integerCodec.encode(writer, value.getPageCount(), encoderContext);
        writer.writeEndDocument();
    }
    // Defines a decode() method to convert BSON values to Book field values
    @Override
    public Book decode(BsonReader reader, DecoderContext decoderContext) {
        Book book = new Book();
        reader.readStartDocument();
        while (reader.readBsonType() != BsonType.END_OF_DOCUMENT) {
            String fieldName = reader.readName();
            if (fieldName.equals("title")) {
                book.setTitle(stringCodec.decode(reader, decoderContext));
            } else if (fieldName.equals("readStatus")) {
                book.setReadStatus(readStatusCodec.decode(reader, decoderContext));
            } else if (fieldName.equals("pageCount")) {
                book.setPageCount(integerCodec.decode(reader, decoderContext));
            } else if (fieldName.equals("_id")) {
                reader.readObjectId();
            } else {
                reader.skipValue();
            }
        }
        reader.readEndDocument();
        return book;
    }
    // Returns an instance of the Book class, since Java cannot infer the class type
    @Override
    public Class<Book> getEncoderClass() {
        return Book.class;
    }
}

public class BookCodecProvider implements CodecProvider {
    public BookCodecProvider() {}
    @Override
    @SuppressWarnings("unchecked")
    public <T> Codec<T> get(Class<T> clazz, CodecRegistry registry) {
        if (clazz == Book.class) {
            return (Codec<T>) new BookCodec(registry);
        }
        // return null when not a provider for the requested class
        return null;
    }
}

public class BookCodecExample {
    public static void main(String[] args) {
        String uri = "<MongoDB connection URI>";
        try (MongoClient mongoClient = MongoClients.create(uri)) {
            CodecRegistry codecRegistry = CodecRegistries.fromRegistries(
                    CodecRegistries.fromCodecs(new ReadStatusCodec()),
                    CodecRegistries.fromProviders(new BookCodecProvider()),
                    MongoClientSettings.getDefaultCodecRegistry());
            MongoDatabase database = mongoClient.getDatabase("codecs_example_db");
            MongoCollection<Book> collection = database.getCollection("books", Book.class)
                    .withCodecRegistry(codecRegistry);
            // construct and insert an instance of Book
            Book myBook = new Book();
            myBook.setTitle("The Hobbit");
            myBook.setReadStatus(ReadStatus.READ);
            myBook.setPageCount(310);
            Mono.from(collection.insertOne(myBook)).block();
            // retrieve one or more instances of Book
            Flux.from(collection.find())
                    .doOnNext(System.out::println)
                    .blockLast();
        }
    }
}