从 MongoDB 读取数据

1
import com.mongodb.ConnectionString
2
import com.mongodb.MongoClientSettings
3
import com.mongodb.client.model.*
4
import com.mongodb.kotlin.client.*
5
import org.bson.Document
6
7
fun main() {
8
    val uri = "<connection string URI>"
9
    
10
    val settings = MongoClientSettings.builder()
11
        .applyConnectionString(ConnectionString(uri))
12
        .retryWrites(true)
13
        .build()
14
15
    // Create a new client and connect to the server
16
    val mongoClient = MongoClient.create(settings)
17
    val database = mongoClient.getDatabase("<database name>")
18
    val collection = database.getCollection<Document>("<collection name>")
19
20
    // Start example code here
21
22
    // End example code here
23
}

val filter = <filter>
val results = collection.find(filter)
results.forEach { result ->
    print(result)
}

val count = collection.countDocuments()
print(count)

val filter = <filter>
val queryCount = collection.countDocuments(filter)
print(queryCount)

val estimatedCount = collection.estimatedDocumentCount()
print(estimatedCount)

val distinctResults = collection.distinct("<field name>")
distinctResults.forEach { result ->
    print(result)
}

val changeStream = collection.watch()
changeStream.forEach { changeEvent ->
    print(changeEvent)
}