Work with Extended JSON Data

Extended JSON Examples

The following examples show a document containing an ObjectId, date, and long number field represented in each Extended JSON format. Click the tab that corresponds to the format of the example you want to see:

{
  "_id": { "$oid": "573a1391f29313caabcd9637" },
  "createdAt": { "$date": { "$numberLong": "1601499609" }},
  "numViews": { "$numberLong": "36520312" }
}

{
  "_id": { "$oid": "573a1391f29313caabcd9637" },
  "createdAt": { "$date": "2020-09-30T18:22:51.648Z" },
  "numViews": 36520312
}

{
  "_id": ObjectId("573a1391f29313caabcd9637"),
  "createdAt": ISODate("2020-09-30T18:22:51.648Z"),
  "numViews": NumberLong("36520312")
}

Use the Document Classes

To read a Extended JSON string into a Kotlin document object, call the parse() static method from the Document or BsonDocument class. This method parses the Extended JSON string and stores its data in an instance of the specified document class.

The following example uses the parse() method to read an Extended JSON string into a Document object:

val ejsonStr = """
    {
        "_id": { "$${"oid"}": "507f1f77bcf86cd799439011" },
        "myNumber": { "$${"numberLong"}": "4794261" }
    }
""".trimIndent()
val doc = Document.parse(ejsonStr)
println(doc)

Document{{_id=507f1f77bcf86cd799439011, myNumber=4794261}}

Use the JsonReader Class

To read an Extended JSON string into Kotlin objects without using the Kotlin Sync driver's document classes, use the BSON library's JsonReader class. This class contains methods to sequentially parse the fields and values of the Extended JSON string and return them as Kotlin objects. The driver's document classes also use this class to parse Extended JSON.

The following code uses methods provided by the JsonReader class to convert an Extended JSON string into Kotlin objects:

val string = """
    {
        "_id": { "$${"oid"}": "507f1f77bcf86cd799439011" },
        "myNumber": { "$${"numberLong"}": "4794261" }
    }
""".trimIndent()
val jsonReader = JsonReader(string)
jsonReader.readStartDocument()
// Reads the "_id" field value
jsonReader.readName("_id")
val id = jsonReader.readObjectId()
// Reads the "myNumber" field value 
jsonReader.readName("myNumber")
val myNumber = jsonReader.readInt64()
jsonReader.readEndDocument()
println("$id is type: ${id::class.qualifiedName}")
println("$myNumber is type: ${myNumber::class.qualifiedName}")
jsonReader.close()

507f1f77bcf86cd799439011 is type: org.bson.types.ObjectId
4794261 is type: kotlin.Long

Use the Document Classes

To write an Extended JSON string from a Document or BsonDocument object, call the toJson() method. You can pass this method a JsonWriterSettings object parameter to specify the Extended JSON format.

The following example writes Document data as Relaxed mode Extended JSON:

val doc = Document()
    .append("_id", ObjectId("507f1f77bcf86cd799439012"))
    .append("createdAt", Date.from(Instant.ofEpochMilli(1601499609000L)))
    .append("myNumber", 4794261)
val settings = JsonWriterSettings.builder()
    .outputMode(JsonMode.RELAXED)
    .build()
println(doc.toJson(settings))

{"_id": {"$oid": "507f1f77bcf86cd799439012"}, "createdAt": {"$date": "2020-09-30T21:00:09Z"}, "myNumber": 4794261}

Use the JsonWriter Class

To output an Extended JSON string from data stored in Kotlin objects, you can use the BSON library's JsonWriter class. To construct a JsonWriter object, pass a subclass of a Java Writer to specify how you want to output the Extended JSON. Optionally, you can pass a JsonWriterSettings instance to specify options, such as the Extended JSON format. By default, JsonWriter uses the Relaxed mode format. The Kotlin Sync driver's document classes also use this class to convert BSON to Extended JSON.

The following example uses a JsonWriter object to create Canonical mode Extended JSON string values and output them to System.out:

 val settings = JsonWriterSettings.builder()
    .outputMode(JsonMode.EXTENDED)
    .build()
JsonWriter(BufferedWriter(OutputStreamWriter(System.out)), settings).use { jsonWriter ->
    jsonWriter.writeStartDocument()
    jsonWriter.writeName("_id")
    jsonWriter.writeObjectId(ObjectId("507f1f77bcf86cd799439012"))
    jsonWriter.writeName("myNumber")
    jsonWriter.writeInt64(11223344L)
    jsonWriter.writeEndDocument()
    jsonWriter.flush()
}

{"_id": {"$oid": "507f1f77bcf86cd799439012"}, "myNumber": {"$numberLong": "11223344"}}