MongoDB Basics: Getting Started with CRUD in JAVA

Introduction

MongoDB is a documentary representative in the NoSQL world, and CRUD is easy to implement. It is easy to summarize using the CRUD API in JAVA.

Driver library introduction

build.gradle

// https://mvnrepository.com/artifact/org.mongodb/mongo-java-driver
compileInclude group: 'org.mongodb', name: 'mongo-java-driver', version: '3.11.0'

Create

Insert image

JAVA insert sample

MongoDBTest.java

package mongodb;

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;

import org.bson.Document;

public class MongoDBTest {

	public static void main(String[] args) {
		//Generate MongoDB clients
		MongoClient client = MongoClients.create("mongodb://localhost:27017");
		//Get a DB object
		MongoDatabase db = client.getDatabase("mydb");
		//Get a user collection
		MongoCollection<Document> users = db.getCollection("users");

		//Set user attributes
		Document user = new Document();
		user.append("lastName", "tanaka");
		user.append("firstName", "ichiro");
		user.append("gender", "male");

		//Insert into DB
		users.insertOne(user);

		//Close the client
		client.close();
	}
}

Collection image

Multiple inserts

List<Document> userList = new ArrayList<Document>();
		
Document user1 = new Document();
user1.append("lastName", "tanaka");
		
Document user2 = new Document();
user2.append("lastName", "yamada");
		
userList.add(user1);
userList.add(user2);
		
//Insert list into DB
users.insertMany(userList);

Read

Search image

Find One Get the first one with the feeling of db.collection.find (filter) .first (). If you want to search by _id, the first method is convenient.

MongoDBTest.java

package mongodb;

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.Filters;

import org.bson.Document;
import org.bson.types.ObjectId;

public class MongoDBTest {

	public static void main(String[] args) {
		//Generate MongoDB clients
		MongoClient client = MongoClients.create("mongodb://localhost:27017");
		//Get a DB object
		MongoDatabase db = client.getDatabase("mydb");
		//Get a user collection
		MongoCollection<Document> users = db.getCollection("users");

		// _Search by id
		Document user = users.find(Filters.eq("_id", new ObjectId("5d858b36c491de05900c4e32"))).first();
		if (user != null) {
			System.out.println("lastName:" + user.getString("lastName"));
		}

		//Close the client
		client.close();
	}
}

output:

lastName:tanaka

Find List It is possible to narrow down by passing the search condition to the parameter of the find method. Various methods are provided in the Filters class.

Search sample

//Search for multiple people by surname
MongoCursor<Document> cursor = users.find(Filters.or(Filters.in("lastName", "tanaka", "yamada"))).cursor();
while (cursor.hasNext()) {
    Document user = (Document) cursor.next();
    // do something
}

//It is also convenient to convert to a list instead of a Cursor.
// List<Document> documents = users.find(Filters.or(Filters.in("lastName", "tanaka", "yamada"))).into(new ArrayList<Document>());

Sort, skip, limit, etc.

Document sort = new Document();
sort.append("updateDate", -1);
MongoCursor<Document> cursor = users.find(Filters.in("lastName", "tanaka", "yamada")).sort(sort).skip(20).limit(10).cursor();

Update

Update image

Update One

Update one data with updateOne method

MongoDBTest.java

package mongodb;

import com.mongodb.client.MongoClient;
import com.mongodb.client.MongoClients;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;

import java.util.Date;

import org.bson.Document;
import org.bson.types.ObjectId;

public class MongoDBTest {

	public static void main(String[] args) {
		//Generate MongoDB clients
		MongoClient client = MongoClients.create("mongodb://localhost:27017");
		//Get a DB object
		MongoDatabase db = client.getDatabase("mydb");
		//Get a user collection
		MongoCollection<Document> users = db.getCollection("users");
		
		//Update conditions
		Document filter = new Document();
		filter.append("_id", new ObjectId("5d858b36c491de05900c4e32"));
		
		//Update data
		Document updateSet = new Document();
		updateSet.append("lastName", "Suzuki");
		updateSet.append("updateDate", new Date());
		
		//update object
		Document update = new Document();
		update.append("$set", updateSet);
		
		//update
		users.updateOne(filter , update);
		
		//Close the client
		client.close();
	}
}

Updated collection data

Update Many If you want to update the data that matches the conditions, use the updateMany method.

Update Manual: https://docs.mongodb.com/manual/tutorial/update-documents/

Replace One If you want to completely replace the document instead of updating some data, use the replaceOne method.

//Update conditions
Document filter = new Document();
filter.append("_id", new ObjectId("5d858b36c491de05900c4e32"));
		
//Update data
Document update = new Document();
update.append("lastName", "Suzuki");
update.append("updateDate", new Date());
		
//Replacement
users.replaceOne(filter, update);

One point to note is that if you process the document searched in the DB as replacement data, an error will occur. bad example:

//Get data from DB
Document user = users.find(Filters.eq("_id", new ObjectId("5d858b36c491de05900c4e32"))).first();
user.append("memo", "new user");
		
//Replacement(Wrong_Since it is an id, an error will occur. the same_If it is id, there is no problem.)
users.replaceOne(Filters.eq("_id", new ObjectId("5d859c77b64c3286a4d29d90")), user);

If the _id is different, you can clear the error by deleting the user's _id field. If you have Version data, you may want to use the replaceOne method.

//Get data from DB
Document user = users.find(Filters.eq("_id", new ObjectId("5d858b36c491de05900c4e32"))).first();
user.append("memo", "new user");
user.remove("_id");

Delete

Deleted image

deleteOne users.deleteOne(Filters.eq("_id", new ObjectId("5d859c77b64c3286a4d29d90")));

deleteMany ʻUsers.deleteMany (Filters.eq ("lastName", "Suzuki")); `

Delete related methods

Manual: https://docs.mongodb.com/manual/ CRUD (image of the text): https://docs.mongodb.com/manual/crud/

that's all