java - 如何让 MongoCollectoin 返回 java.sql.Timestamp？

Question

基于https://jira.mongodb.org/browse/JAVA-1741我正在尝试实现和使用 TimestampCodec，并期望在读取 MongoCollection 时使用decode()，但由于某种原因，decode() 不是 执行后，数据库中的 IsoDate 值将转换为 java.util.Date，而不是预期的 java.sql.Timestamp。

检索 MongoCollection 时使用 TimestampCodec.decode() 的正确方法是什么？

我有以下内容，但失败并显示 java.lang.AssertionError: Expected: but was:

@Test
public void testTimestamp() {
    Map<BsonType, Class<?>> replacements = new HashMap<BsonType, Class<?>>();
    replacements.put(BsonType.DATE_TIME, Timestamp.class);
    BsonTypeClassMap bsonTypeClassMap = new BsonTypeClassMap(replacements);
    DocumentCodecProvider documentCodecProvider =
            new DocumentCodecProvider(bsonTypeClassMap);
    CodecRegistry codecRegistry = CodecRegistries.fromRegistries(
    CodecRegistries.fromCodecs(
            new TimestampCodec()),
            MongoClient.getDefaultCodecRegistry(),
            CodecRegistries.fromProviders(documentCodecProvider));
    Builder optionsBuilder = new MongoClientOptions.Builder();
    optionsBuilder.codecRegistry(MongoCodecs.codecRegistry());
    MongoClientOptions options = optionsBuilder.build();
    MongoClient mongo = new MongoClient(new ServerAddress(), options);
    MongoDatabase db = mongo.getDatabase("mydb");
    MongoCollection<Document> collection = db.getCollection("test");
    try {
        collection.insertOne(new Document("date", new Timestamp(new Date().getTime())));
        assertEquals(Timestamp[].class, collection.find().first().get("date").getClass());
    } finally {
        collection.drop();
        mongo.close();
    }
}

Answer 1

除了小错误之外，解决方案是更改编解码器注册表的顺序，使 MongoClient.getDefaultCodecRegistry() 成为最后一个。

正确的代码是:

@Test
public void testTimestamp() {
    Map<BsonType, Class<?>> replacements = new HashMap<BsonType, Class<?>>();
    replacements.put(BsonType.DATE_TIME, Timestamp.class);
    BsonTypeClassMap bsonTypeClassMap = new BsonTypeClassMap(replacements);
    DocumentCodecProvider documentCodecProvider =
            new DocumentCodecProvider(bsonTypeClassMap);
    CodecRegistry codecRegistry = CodecRegistries.fromRegistries(
            CodecRegistries.fromCodecs(
                    new TimestampCodec()),
            CodecRegistries.fromProviders(documentCodecProvider),
            MongoClient.getDefaultCodecRegistry());
    Builder optionsBuilder = new MongoClientOptions.Builder();
    optionsBuilder.codecRegistry(codecRegistry);
    MongoClientOptions options = optionsBuilder.build();
    MongoClient mongo = new MongoClient(new ServerAddress(), options);
    MongoDatabase db = mongo.getDatabase("mydb");
    MongoCollection<Document> collection = db.getCollection("test");
    try {
        collection.insertOne(new Document("date", new Timestamp(new Date().getTime())));
        assertEquals(Timestamp.class, collection.find().first().get("date").getClass());
    } finally {
        collection.drop();
        mongo.close();
    }
}