How to Install MongoDB C++ Driver?

MongoDB C++ Driver

For software developers who want to use the C++ programming language to communicate with MongoDB databases, the MongoDB C++ Driver is an essential component. The fact that MongoDB is developed in C++ may help developers of applications written in the same language. MongoDB, Inc. officially supports several drivers, including the C++ driver, ensuring maintenance and compatibility.

MongoDB Driver Purpose and Functions Generally, applications use MongoDB drivers to interface with servers. The API matches the programming language’s idioms while providing a uniform interface across languages. Although the syntax may change, the underlying operations are the same.

All MongoDB drivers, including the C++ driver, carry out the following essential tasks:

Object ID Generation: MongoDB Object IDs, which are the default values for the _id field in all documents, are created by drivers.

BSON Conversion: They translate documents’ language-specific representations (such C++ objects and structures) into and out of Binary JSON (BSON). MongoDB internally uses a lightweight binary format called BSON for network communication and disc storage of documents. Since developers usually deal with native C++ data structures and let the driver handle the serialisation, this automatic translation makes data handling easier for them.

Wire Protocol Communication: The MongoDB wire protocol is used by drivers to connect to the MongoDB database via a TCP socket. BSON data is effectively wrapped in a thin layer by this protocol.

Using the C++ Driver

An Example of C++ Driver Use We can create a representative excerpt from demonstrate fundamental interaction, even though entire C++ examples are scattered. Example: connecting to MongoDB, querying, and retrieving data.

A C++ MongoDB driver application typically involves:

1. Connecting to the database: Establishing a communication connection with the Mongod instance involves connecting to the database.
2. Building a query: Flexible and ad hoc query capabilities are made possible by the use of BSON objects in query construction.
3. Executing the query and processing results: The driver offers ways to transmit the query and iterate through the returned document cursor in order to execute the query and process the results.

#include "client/dbclient.h" //  - Note: This header might vary for modern drivers
using namespace mongo; //
// Function to demonstrate connecting and querying
void queryDocuments() {
    try {
        // Connect to MongoDB instance on localhost:27017 (default port)
        // Note: In modern drivers, MongoClient is often used, but DBClientBase is shown in C++ examples
        DBClientBase& conn = *new DBClientConnection(); // Simplified connection, actual setup might be more robust
        conn.connect("localhost:27017"); // Connect to a running mongod instance
        std::cout << "Connection to database successfully" << std::endl; // Similar to PHP example
        // Assume a collection named 'mycol' exists and contains documents
        // Example document structure (JSON-like): { "by": "tutorials point", "title": "MongoDB Overview" } 
        // Build a query document using BSON syntax
        // This is analogous to db.mycol.find({"by":"tutorials point","title": "MongoDB Overview"}) 
        BSONObj query = BSON("by" << "tutorials point" << "title" << "MongoDB Overview"); // 
        // Execute the find query
        // The conn.query method can return a cursor 
        std::auto_ptr<DBClientCursor> cursor = conn.query("test.mycol", query); // "test.mycol" combines database and collection name
        std::cout << "Found documents:" << std::endl;
        // Iterate through the results from the cursor
        while (cursor->more()) { //  - Check if there are more documents in the cursor
            BSONObj p = cursor->next(); //  - Retrieve the next document
            std::cout << p.toString() << std::endl; // Convert BSON object to string for printing
        }
    } catch (const mongo::DBException &e) {
        std::cerr << "Caught exception: " << e.what() << std::endl;
    }
}
// int main() {
//    queryDocuments();
//    return 0;
// }

Explanation of the C++ Code Snippet:

• “client/dbclient.h” is included, and namespace mongo;: The environment required to use the MongoDB C++ driver is built up by these lines. Newer driver versions may alter the specific header, however DBClientBase is a basic connection type.
• Connecting to a MongoDB server on the default port is conn.connect(“localhost:27017”).
• BSONObj query = BSON(“by” < “tutorials point” “title” “MongoDB Overview”);: In C++, the BSON macro makes building BSON objects easy. This shows how to generate a query. Find documents with “by” “tutorials point” and “title” “MongoDB Overview” with this query. Using MongoDB’s document model requires this BSON object construction function.
• Auto_ptr std:: conn.query(“test.mycol”, query); cursor = Using the created query, the query method on the connection object performs the find operation against the designated collection (test.mycol). A DBClientCursor object is returned. Cursors are iterable objects that enable effective document retrieval by storing the entire set of query results.
• BSONObj p = cursor->next(); } while (cursor->more()) {… This loop iterates across cursor-returned documents. cursor->more() checks for more documents and cursor->next() finds the next BSONObj.

Functionalities of the C++ Driver

Numerous database operations are made possible via the C++ driver:

1. Querying Data: Building and running queries is made possible by the C++ driver. Traditional SQL injection attacks are less likely to occur with MongoDB since queries are expressed as BSON objects. For instance, a BSON object can be used to construct a query:
2. To retrieve results, this snippet shows how to create a BSON object for the query and then use it with the query method.
3. Tailable Cursors: Mostly utilised with capped collections, tailable cursors are supported by the C++ driver. When their size reaches maximum, capped collections eliminate the oldest documents. Tailable cursors, like Unix tail -f, wait for new documents to be added to the capped collection after providing the original results. This is handy for real-time logs and social media streams.
4. To track the last document accessed, the tail function in this code initialises lastValue. After that, it constantly searches a capped collection (ns) for new data by entering an endless loop (while(1)). The cursor stays open and waits for fresh data for a few seconds thanks to the QueryOption_CursorTailable and QueryOption_AwaitData settings. The query is restarted from the lastValue if the cursor dies.
5. Authentication: Kerberos authentication for MongoDB deployments is supported by the C++ driver. X.509 certificate authentication is another option.
6. SSL/TLS Connections: MongoDB-encrypted network traffic is supported by the C++ driver via SSL/TLS.
7. Replica Set Health Monitoring: In order to support systems that need authentication, the C++ driver as of MongoDB 2.6 uses the isMaster command to monitor replica set health rather than replSetGetStatus.
8. GridFS: MongoDB drivers typically function with GridFS, a specification for storing big files in MongoDB using standard documents, despite the fact that no explicit C++ code is offered for GridFS.
9. Limitations (DBRefs): C++ driver “contains no support for DBRefs” and necessitates manual reference traversal. A reference to a document is identified by its _id, collection name, and optional database name according to the DBRefs convention.

Developers must understand these C++ driver elements to construct reliable and fast MongoDB apps. C++ driver 1.0.0 is minimum compatible with MongoDB 3.0.