基于 vCore 的 Azure Cosmos DB for MongoDB 上的更改流 (预览版)

// Open a change stream
const changeStream = db.exampleCollection.watch();

// Listen for changes
while (changeStream.hasNext()) 
    {
        const change = changeStream.next();
        printjson(change);
    }

package com.example;
 
import com.mongodb.MongoClientSettings;
import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.model.changestream.ChangeStreamDocument;
 
import org.bson.BsonDocument;
import org.bson.Document;
import org.bson.json.JsonWriterSettings;
import org.json.JSONObject;
 
public class ChangeStreamExample {
    public static void main(String[] args) {
        MongoClient mongoClient = MongoClients.create("mongodb://<username>:<pwd>@<clustername>.global.mongocluster.cosmos.azure.com/?tls=true");
        MongoDatabase database = mongoClient.getDatabase("test");
        MongoCollection<Document> collection = database.getCollection("test");
 
        // Open a change stream
        MongoCursor<ChangeStreamDocument<Document>> cursor = collection.watch().iterator();
 
        // Listen for changes
        try {
            while (cursor.hasNext()) {
                ChangeStreamDocument<Document> change = cursor.next();
 
                // Create a JSONObject from the fields of the ChangeStreamDocument
                JSONObject json = new JSONObject();
 
                // Add fields to the JSON object
                json.put("operationType", change.getOperationType().getValue());
                json.put("namespace", change.getNamespace().getFullName());
 
                if (change.getDocumentKey() != null) {
                    json.put("documentKey", change.getDocumentKey().toJson().toString());
                }
 
                if (change.getResumeToken() != null) {
                    json.put("resumeToken", change.getResumeToken().toJson());
                }
 
                if (change.getFullDocument() != null) {
                    json.put("fullDocument", change.getFullDocument().toJson());
                }
 
                if (change.getWallTime() != null) {
                    json.put("wallTime", change.getWallTime().toString());
                }
 
                // Pretty-print the JSON object with 4-space indent
                System.out.println(json.toString(4)); 
            }
        } 
        catch (Exception e) {
            System.err.println("Error processing change stream: " + e);
        } 
        finally {
            cursor.close();
            mongoClient.close();
        }
    }
}

在此更改流事件中，我们看到一条新记录 inserted 到 cs 数据库中的 exampleCollection 集合中，事件详细信息包括新添加的文档的完整内容。

{
  "_id": { "_data": "AeARBpQ/AAAA" }, // "resume_token"
  "operationType": "insert",
  "fullDocument": {
    "_id": { "$oid": "66e6f63e6f49ecaabf794958" },
    "employee_id": "17986",
    "name": "John",
    "position": "Software Engineer",
    "department": "IT",
    "rating": 4
  },
  "ns": { "db": "cs", "coll": "exampleCollection" },
  "documentKey": { "_id": { "$oid": "66e6f63e6f49ecaabf794958" } }
}

在此更新事件中，John 的 position 和 rating 被修改。 更改流反映 exampleCollection 集合中的 update 以及文档的更新后状态。

{
  "_id": { "_data": "AWACAKM/AAAA" },
  "operationType": "update",
  "fullDocument": {
    "_id": { "$oid": "66e6f63e6f49ecaabf794958" },
    "employee_id": "17986",
    "name": "John",
    "position": "SSE",
    "department": "IT",
    "rating": 5
  },
  "ns": {
    "db": "cs", "coll": "exampleCollection"
  },
  "documentKey": {
    "_id": { "$oid": "66e6f63e6f49ecaabf794958" }
  }
}

更改流事件指示文档是来自 cs 数据库中的 exampleCollection 集合的 deleted。 该事件会捕获已删除文档的唯一标识符。

{
  "_id": { "_data": "ASgBAJs/AAAA" },
  "operationType": "delete",
  "ns": { "db": "cs", "coll": "exampleCollection" },
  "documentKey": { "_id": { "$oid": "66e6f63e6f49ecaabf794958" } }
}