Spring boot: MongoDB: Hello World Application

Step 1: Create Employee entity class.

@Document("employees")
public class Employee {
 @Id
 private String id;

 private String firstName;

 private String lastName;

 .......
 .......

}

@Document("employees")

Above statement tells to store the object of type Employee to employees collection in MongoDB.

Step 2: Create EmployeeRepository interface by extending MongoRepository interface.

@Repository
public interface EmployeeRepository extends MongoRepository<Employee, String> {

}

Step 3: Specify mongoDB instance details in applicaton.properties file.

spring.data.mongodb.database=myorg

spring.data.mongodb.port=27017

spring.data.mongodb.host=localhost

Step 4: Use EmployeeRepository instance to perform CRUD operations against MongoDB database.

Employee emp1 = new Employee("Phalgun", "Garimella");

Employee emp2 = new Employee("Sankalp", "Dubey");

Employee emp3 = new Employee("Arpan", "Debroy");

empRepository.saveAll(Arrays.asList(emp1, emp2, emp3));

empRepository.findAll().forEach(System.out::println);

Find the below working application.

Employee.java

package com.sample.app.entity;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document("employees")
public class Employee {
 @Id
 private String id;

 private String firstName;

 private String lastName;

 public Employee(String firstName, String lastName) {
  this.firstName = firstName;
  this.lastName = lastName;
 }

 public String getId() {
  return id;
 }

 public void setId(String id) {
  this.id = id;
 }

 public String getFirstName() {
  return firstName;
 }

 public void setFirstName(String firstName) {
  this.firstName = firstName;
 }

 public String getLastName() {
  return lastName;
 }

 public void setLastName(String lastName) {
  this.lastName = lastName;
 }

 @Override
 public String toString() {
  StringBuilder builder = new StringBuilder();
  builder.append("Employee [id=").append(id).append(", firstName=").append(firstName).append(", lastName=")
    .append(lastName).append("]");
  return builder.toString();
 }

}

EmployeeRepository.java

package com.sample.app.repository;

import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.stereotype.Repository;

import com.sample.app.entity.Employee;

@Repository
public interface EmployeeRepository extends MongoRepository<Employee, String> {

}

App.java

package com.sample.app;

import java.util.Arrays;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.data.mongodb.core.MongoOperations;
import org.springframework.data.mongodb.core.MongoTemplate;

import com.mongodb.MongoClient;
import com.sample.app.entity.Employee;
import com.sample.app.repository.EmployeeRepository;

@SpringBootApplication
public class App {
 @Value("${spring.data.mongodb.database}")
 private String database;

 @Value("${spring.data.mongodb.host}")
 private String host;

 @Value("${spring.data.mongodb.port}")
 private int port;
 
 @Autowired
 private EmployeeRepository empRepository;

 public static void main(String[] args) {

  SpringApplication.run(App.class, args);
 }

 public void dropPreviousData() {
  MongoClient mongoClient = new MongoClient(host, port);

  MongoOperations mongoOps = new MongoTemplate(mongoClient, database);

  mongoOps.dropCollection("employees");
 }
 @Bean
 public CommandLineRunner demo() {
  return (args) -> {

   dropPreviousData();
   
   Employee emp1 = new Employee("Phalgun", "Garimella");
   Employee emp2 = new Employee("Sankalp", "Dubey");
   Employee emp3 = new Employee("Arpan", "Debroy");

   empRepository.saveAll(Arrays.asList(emp1, emp2, emp3));

   empRepository.findAll().forEach(System.out::println);
   

  };
 }
}

Create ‘application.properties’ file under src/main/resources’ folder.

application.properties

spring.data.mongodb.database=myorg
spring.data.mongodb.port=27017
spring.data.mongodb.host=localhost

logging.level.org.springframework.data=WARN

Update pom.xml with dependencies.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 <modelVersion>4.0.0</modelVersion>
 <groupId>springDataMongo</groupId>
 <artifactId>springDataMongo</artifactId>
 <version>1</version>

 <parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.1.6.RELEASE</version>
 </parent>

 <dependencies>
  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-data-mongodb</artifactId>
  </dependency>
 </dependencies>
</project>

Total project structure looks like below.

Run App.java, you can see below messages in console.

Employee [id=5d5149a05d30d037a2fd39a4, firstName=Phalgun, lastName=Garimella]
Employee [id=5d5149a05d30d037a2fd39a5, firstName=Sankalp, lastName=Dubey]
Employee [id=5d5149a05d30d037a2fd39a6, firstName=Arpan, lastName=Debroy]

Connect to mongoDB instance by executing the command ‘mongo’ in a terminal. 

> use myorg;
switched to db myorg
> 
> db.employees.find();
{ "_id" : ObjectId("5d513ec55d30d036dbfcc548"), "firstName" : "Phalgun", "lastName" : "Garimella", "_class" : "com.sample.app.entity.Employee" }
{ "_id" : ObjectId("5d513ec55d30d036dbfcc549"), "firstName" : "Sankalp", "lastName" : "Dubey", "_class" : "com.sample.app.entity.Employee" }
{ "_id" : ObjectId("5d513ec55d30d036dbfcc54a"), "firstName" : "Arpan", "lastName" : "Debroy", "_class" : "com.sample.app.entity.Employee" }
>

You can download complete working application from this link.

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