Example usage for com.mongodb.client MongoCollection watch

Introduction

In this page you can find the example usage for com.mongodb.client MongoCollection watch.

Prototype

ChangeStreamIterable<TDocument> watch();

Source Link

Document

Creates a change stream for this collection.

Usage

From source file:documentation.ChangeStreamSamples.java

License:Apache License

/**
 * Run this main method to see the output of this quick example.
 *
 * @param args takes an optional single argument for the connection string
 *//*from  w w w  .  j  a v  a  2 s.  c  o m*/
public static void main(final String[] args) {
    MongoClient mongoClient;

    if (args.length == 0) {
        // connect to the local database server
        mongoClient = MongoClients.create("mongodb://localhost:27017,localhost:27018,localhost:27019");
    } else {
        mongoClient = MongoClients.create(args[0]);
    }

    // Select the MongoDB database.
    MongoDatabase database = mongoClient.getDatabase("testChangeStreams");
    database.drop();
    sleep();

    // Select the collection to query.
    MongoCollection<Document> collection = database.getCollection("documents");

    /*
     * Example 1
     * Create a simple change stream against an existing collection.
     */
    System.out.println("1. Initial document from the Change Stream:");

    // Create the change stream cursor.
    MongoChangeStreamCursor<ChangeStreamDocument<Document>> cursor = collection.watch().cursor();

    // Insert a test document into the collection.
    collection.insertOne(Document.parse("{username: 'alice123', name: 'Alice'}"));
    ChangeStreamDocument<Document> next = cursor.next();
    System.out.println(next);
    cursor.close();
    sleep();

    /*
     * Example 2
     * Create a change stream with 'lookup' option enabled.
     * The test document will be returned with a full version of the updated document.
     */
    System.out.println("2. Document from the Change Stream, with lookup enabled:");

    // Create the change stream cursor.
    cursor = collection.watch().fullDocument(FullDocument.UPDATE_LOOKUP).cursor();

    // Update the test document.
    collection.updateOne(Document.parse("{username: 'alice123'}"),
            Document.parse("{$set : { email: 'alice@example.com'}}"));

    // Block until the next result is returned
    next = cursor.next();
    System.out.println(next);
    cursor.close();
    sleep();

    /*
     * Example 3
     * Create a change stream with 'lookup' option using a $match and ($redact or $project) stage.
     */
    System.out.println(
            "3. Document from the Change Stream, with lookup enabled, matching `update` operations only: ");

    // Insert some dummy data.
    collection.insertMany(asList(Document.parse("{updateMe: 1}"), Document.parse("{replaceMe: 1}")));

    // Create $match pipeline stage.
    List<Bson> pipeline = singletonList(
            Aggregates.match(Filters.or(Document.parse("{'fullDocument.username': 'alice123'}"),
                    Filters.in("operationType", asList("update", "replace", "delete")))));

    // Create the change stream cursor with $match.
    cursor = collection.watch(pipeline).fullDocument(FullDocument.UPDATE_LOOKUP).cursor();

    // Forward to the end of the change stream
    next = cursor.tryNext();

    // Update the test document.
    collection.updateOne(Filters.eq("updateMe", 1), Updates.set("updated", true));
    next = cursor.next();
    System.out.println(format("Update operationType: %s %n %s", next.getUpdateDescription(), next));

    // Replace the test document.
    collection.replaceOne(Filters.eq("replaceMe", 1), Document.parse("{replaced: true}"));
    next = cursor.next();
    System.out.println(format("Replace operationType: %s", next));

    // Delete the test document.
    collection.deleteOne(Filters.eq("username", "alice123"));
    next = cursor.next();
    System.out.println(format("Delete operationType: %s", next));
    cursor.close();
    sleep();

    /**
     * Example 4
     * Resume a change stream using a resume token.
     */
    System.out.println("4. Document from the Change Stream including a resume token:");

    // Get the resume token from the last document we saw in the previous change stream cursor.
    BsonDocument resumeToken = cursor.getResumeToken();
    System.out.println(resumeToken);

    // Pass the resume token to the resume after function to continue the change stream cursor.
    cursor = collection.watch().resumeAfter(resumeToken).cursor();

    // Insert a test document.
    collection.insertOne(Document.parse("{test: 'd'}"));

    // Block until the next result is returned
    next = cursor.next();
    System.out.println(next);
    cursor.close();
}

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