Spring Data JPA: findById: Get an entity by id

CrudRepository interface provides 'findById' method, it is used to retrieve an entity by id.

Optional<T> findById(ID id)

Returns the entity with the given id or Optional.empty() if none found.

Example

Employee emp1 = Employee.builder().firstName("Ram").lastName("Gurram").build();

Employee persistedEmployee = employeeRepository.save(emp1);

Optional<Employee> empOpt = employeeRepository.findById(persistedEmployee.getId());

if (!empOpt.isPresent()) {
    System.out.println("Employee is not exist for given id");
} else {
    printEmployee(empOpt.get());
}

Find the below working application.

Step 1: Create model class Employee.

Employee.java

package com.sample.app.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "employee")
public class Employee {
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
 @Column(name = "employee_id")
 private int id;
 
 @Column(name = "first_name")
 private String firstName;
 
 @Column(name = "last_name")
 private String lastName;

 public int getId() {
  return id;
 }

 public void setId(int 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;
 }

 public static EmployeeBuilder builder() {
  return new EmployeeBuilder();
 }

 public static class EmployeeBuilder {
  private Employee emp;

  public EmployeeBuilder() {
   emp = new Employee();
  }

  public EmployeeBuilder firstName(String firstName) {
   emp.setFirstName(firstName);
   return this;
  }

  public EmployeeBuilder lastName(String lastName) {
   emp.setLastName(lastName);
   return this;
  }

  public Employee build() {
   return emp;
  }
 }

 @Override
 public String toString() {
  return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + "]";
 }

}

Step 2: Create EmployeeRepository interface like below.

EmployeeRepository

package com.sample.app.repository;

import org.springframework.data.repository.CrudRepository;

import com.sample.app.model.Employee;  

public interface EmployeeRepository extends CrudRepository<Employee, Integer> {

 
}

Step 3: Create ‘application.properties’ file under src/main/resources.

application.properties

logging.level.root=WARN
logging.level.org.hibernate=ERROR

## H2 specific properties
spring.h2.console.enabled=true
spring.h2.console.path=/h2

spring.datasource.url=jdbc:h2:file:~/db/myOrg.db;DB_CLOSE_ON_EXIT=FALSE;DB_CLOSE_DELAY=-1;

spring.datasource.username=krishna
spring.datasource.password=password123

spring.datasource.driverClassName=org.h2.Driver

## JPA specific properties
# Creates the schema, destroying previous data.
spring.jpa.hibernate.ddl-auto=create

spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true

## Database connection pooling properties
# Number of ms to wait before throwing an exception if no connection is available.
spring.datasource.max-wait=10000

# Maximum number of active connections that can be allocated from this pool at the same time.
spring.datasource.tomcat.max-active=10
spring.datasource.tomcat.max-idle=5
spring.datasource.tomcat.min-idle=3

Step 4: Define App.java class like below.

App.java

package com.sample.app;

import java.util.Optional;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

import com.sample.app.model.Employee;
import com.sample.app.repository.EmployeeRepository;

@SpringBootApplication
public class App {

    private static void printEmployee(Employee emp) {
        System.out.println("------------------------------");
        System.out.println("Id : " + emp.getId());
        System.out.println("firstName : " + emp.getFirstName());
        System.out.println("lastName : " + emp.getLastName());
        System.out.println("------------------------------");
    }

    public static void main(String args[]) {
        SpringApplication.run(App.class, args);
    }

    @Bean
    public CommandLineRunner demo(EmployeeRepository employeeRepository) {
        return (args) -> {
            Employee emp1 = Employee.builder().firstName("Ram").lastName("Gurram").build();

            Employee persistedEmployee = employeeRepository.save(emp1);

            Optional<Employee> empOpt = employeeRepository.findById(persistedEmployee.getId());

            if (!empOpt.isPresent()) {
                System.out.println("Employee is not exist for given id");
            } else {
                printEmployee(empOpt.get());
            }

        };
    }

}

Total project structure looks like below.

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

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.1.6.RELEASE)

Hibernate: 
    
    drop table employee if exists
Hibernate: 
    
    drop sequence if exists hibernate_sequence
Hibernate: create sequence hibernate_sequence start with 1 increment by 1
Hibernate: 
    
    create table employee (
       employee_id integer not null,
        first_name varchar(255),
        last_name varchar(255),
        primary key (employee_id)
    )
Hibernate: 
    call next value for hibernate_sequence
Hibernate: 
    insert 
    into
        employee
        (first_name, last_name, employee_id) 
    values
        (?, ?, ?)
Hibernate: 
    select
        employee0_.employee_id as employee1_0_0_,
        employee0_.first_name as first_na2_0_0_,
        employee0_.last_name as last_nam3_0_0_ 
    from
        employee employee0_ 
    where
        employee0_.employee_id=?
------------------------------
Id : 1
firstName : Ram
lastName : Gurram
------------------------------

You can download the complete working application from this link.

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