Spring boot: MongoDB: Adding custom query methods

Just like any other method in Java, Query methods are also methods that are defined in Repository interface. Query methods must follow below naming conventions.

a.   A query method can return one or more results.

b.   A Query method must starts with 'findBy' clause followed by entity attribute name (Use camel case here)

c.    You can optionally chain subattribute names (Ex: findByAddressCityName)

d.   Query method parameters type must match with the data types of entity attributes.

e.   If a query method returning more than one result, then result type can be List or Stream

Example

@Repository
public interface EmployeeRepository extends MongoRepository<Employee, String> {
 List<Employee> findByFirstName(String firstName);
 
 List<Employee> findByLastName(String lastName);
 
 List<Employee> findByFirstNameAndLastName(String firstName, String lastName);
}

Find the below working example.

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 java.util.List;

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> {
 List<Employee> findByFirstName(String firstName);
 
 List<Employee> findByLastName(String lastName);
 
 List<Employee> findByFirstNameAndLastName(String firstName, String lastName);
}

application.properties

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

logging.level.org.springframework.data=WARN

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>

App.java

package com.sample.app;

import java.util.Arrays;
import java.util.List;

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");
 }

 public void printAllEmployees(String msg) {
  List<Employee> emps = empRepository.findAll();

  System.out.println("\nAll Employees");
  for (Employee emp : emps) {
   System.out.println(emp);
  }
 }

 public void printAllEmployees(List<Employee> emps, String msg) {

  System.out.println("\n" + msg);
  for (Employee emp : emps) {
   System.out.println(emp);
  }
 }

 @Bean
 public CommandLineRunner demo() {
  return (args) -> {

   dropPreviousData();

   Employee emp1 = new Employee("Phalgun", "Garimella");
   Employee emp2 = new Employee("Sankalp", "Dubey");
   Employee emp3 = new Employee("Arpan", "Garimella");
   Employee emp4 = new Employee("Phalgun", "Dubey");

   empRepository.saveAll(Arrays.asList(emp1, emp2, emp3, emp4));

   List<Employee> emps = empRepository.findByFirstName("Phalgun");
   printAllEmployees(emps, "Employee with first name 'Phalgun'");

   emps = empRepository.findByLastName("Dubey");
   printAllEmployees(emps, "Employee with last name 'Dubey'");

   emps = empRepository.findByFirstNameAndLastName("Phalgun", "Garimella");
   printAllEmployees(emps, "Employee with first name 'Phalgun' and lastName 'Garimella'");

  };
 }
}

Total project structure looks like below.

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

Employee with first name 'Phalgun'
Employee [id=5d523cdea65c2b439ccde7fa, firstName=Phalgun, lastName=Garimella]
Employee [id=5d523cdea65c2b439ccde7fd, firstName=Phalgun, lastName=Dubey]

Employee with last name 'Dubey'
Employee [id=5d523cdea65c2b439ccde7fb, firstName=Sankalp, lastName=Dubey]
Employee [id=5d523cdea65c2b439ccde7fd, firstName=Phalgun, lastName=Dubey]

Employee with first name 'Phalgun' and lastName 'Garimella'
Employee [id=5d523cdea65c2b439ccde7fa, firstName=Phalgun, lastName=Garimella]

You can download complete working application from this link

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