Using Java to Operate MongoDB

Using Java to operate MongoDB requires the following steps: 1. Install MongoDB: First, you need to install the MongoDB database and start the MongoDB service. 2. Create a new Maven project and add Java driver dependencies for MongoDB. You can add the following dependencies in the pom.xml file: <dependency> <groupId>org.mongodb</groupId> <artifactId>mongo-java-driver</artifactId> <version>3.12.10</version> </dependency> 3. Connect to the MongoDB database: In Java code, you need to connect to the MongoDB database through the MongoClient object. The following is an example code for connecting to a local MongoDB database: import com.mongodb.MongoClient; import com.mongodb.client.MongoCollection; import com.mongodb.client.MongoDatabase; public class MongoDBConnectionExample { public static void main(String[] args) { //Connect to the local MongoDB database MongoClient mongoClient = new MongoClient("localhost", 27017); //Get Database Objects MongoDatabase database = mongoClient.getDatabase("mydatabase"); //Get Collection Object MongoCollection<Document> collection = database.getCollection("mycollection"); //Add, delete, modify, and query data here // ... //Close the connection to MongoDB mongoClient.close(); } } 4. Insert Data: You can use the insertOne or insertMany methods to insert single or multiple pieces of data into a set. The following is an example code for inserting a single piece of data: import org.bson.Document; // ... //Create a document object to insert Document document = new Document("name", "John") .append("age", 30) .append("email", "john@example.com"); //Insert Single Data collection.insertOne(document); 5. Modify data: You can use the updateOne or updateMany methods to modify data that meets the conditions. The following is an example code for modifying data: import com.mongodb.client.result.UpdateResult; import org.bson.Document; import static com.mongodb.client.model.Filters.*; // ... //Define the conditions to be modified Document filter = new Document("name", "John"); //Define what to modify Document update = new Document("$set", new Document("age", 35)); //Perform modification operations UpdateResult result = collection.updateOne(filter, update); //Number of output modifications System.out.println("Modified documents: " + result.getModifiedCount()); 6. Query data: You can use the find method to query data that meets the conditions. The following is an example code for querying data: import com.mongodb.client.FindIterable; import org.bson.Document; import static com.mongodb.client.model.Filters.*; // ... //Define query criteria Document filter = new Document("age", new Document("$gt", 25)); //Execute query operation FindIterable<Document> documents = collection.find(filter); //Traverse query results for (Document document : documents) { System.out.println(document); } 7. Delete data: You can use the deleteOne or deleteMany methods to delete data that meets the criteria. The following is an example code for deleting data: import com.mongodb.client.result.DeleteResult; import org.bson.Document; import static com.mongodb.client.model.Filters.*; // ... //Define the conditions to delete Document filter = new Document("age", new Document("$lt", 25)); //Perform deletion operation DeleteResult result = collection.deleteMany(filter); //Output the number of deleted items System.out.println("Deleted documents: " + result.getDeletedCount()); These sample codes provide the basic operations for Java operations on MongoDB, including connecting to a database, inserting data, modifying data, querying data, and deleting data. It can be adjusted and expanded according to specific needs.