Spring jpa: Project specific columns using native query

Step 1: Define entity class.

 

Employee.java

@Entity
@Table(name = "my_employee")
public class Employee {
	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	private int id;

	@Column(name = "first_name")
	private String firstName;

	@Column(name = "last_name")
	private String lastName;

	@Column(name = "age")
	private int age;

	@Column(name = "salary")
	private double salary;

	......
	......
}

 

Step 2: Define IEmployee interface with the getter methods that you are interested to extract.

public interface IEmployee {

	int getId();

	String getFirst_name();

	String getLast_name();

}

Below table summarizes the column name and respective native getter method names.

 

Column Name	Method name
id	getId()
first_name	getFirst_name()
last_name	getLast_name()

Step 3: Write a query method to project the result to IEmployee interface.

@Query(value = "select id, first_name,last_name from my_employee", nativeQuery = true)
List<IEmployee> findAllEmpsViaNativeQuery();

As you see the declaration of ‘findAllEmpsViaNativeQuery’ method, the return type is IEmployee interface.

 

Find the below working application.

 

Step 1: Create new maven project ‘raw-sql-projection-demo’.

 

Step 2: Update pom.xml with maven 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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.sample.app</groupId>
	<artifactId>raw-sql-projection-demo</artifactId>
	<version>1</version>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.4.0</version>
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>


	<dependencies>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-data-jpa</artifactId>
		</dependency>


		<dependency>
			<groupId>com.h2database</groupId>
			<artifactId>h2</artifactId>
		</dependency>


	</dependencies>
</project>

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

 

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=false
spring.jpa.properties.hibernate.format_sql=false

## 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

spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true

Step 4: Define Employee entity.

 

Employee.java

package com.sample.app.entity;

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 = "my_employee")
public class Employee {
	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	private int id;

	@Column(name = "first_name")
	private String firstName;

	@Column(name = "last_name")
	private String lastName;

	@Column(name = "age")
	private int age;

	@Column(name = "salary")
	private double salary;

	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 int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public double getSalary() {
		return salary;
	}

	public void setSalary(double salary) {
		this.salary = salary;
	}

	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 EmployeeBuilder age(int age) {
			emp.setAge(age);
			return this;
		}

		public EmployeeBuilder salary(double salary) {
			emp.setSalary(salary);
			return this;
		}

		public Employee build() {
			return emp;
		}
	}

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

}

Step 5: Define IEmployee interface to extract specific columns.

 

IEmployee.java

package com.sample.app.model;

public interface IEmployee {

	int getId();

	String getFirst_name();

	String getLast_name();

}

Step 6: Define EmployeeRepository interface.

 

EmployeeRepository.java

package com.sample.app.repository;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;

import com.sample.app.entity.Employee;
import com.sample.app.model.IEmployee;

public interface EmployeeRepository extends JpaRepository<Employee, Integer> {

	@Query(value = "select id, first_name,last_name from my_employee", nativeQuery = true)
	List<IEmployee> findAllEmpsViaNativeQuery();

	@Query(value = "select id, first_name,last_name from my_employee where first_name=?1", nativeQuery = true)
	List<IEmployee> findAllEmpsByFirstNameViaNativeQuery(String firstName);

}

Step 7: Define main application class.

 

App.java

package com.sample.app;

import java.util.List;

import javax.transaction.Transactional;

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

@SpringBootApplication
public class App {

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

	public void printEmployees(Iterable<Employee> emps, String msg) {
		System.out.println(msg);
		for (Employee emp : emps) {
			System.out.println(emp);
		}

		System.out.println();
	}

	public void printIEmployees(Iterable<IEmployee> emps, String msg) {
		System.out.println(msg);
		for (IEmployee emp : emps) {
			System.out.println(emp.getId() + " , " + emp.getFirst_name() + " , " + emp.getLast_name());
		}

		System.out.println();
	}

	@Bean
	@Transactional
	public CommandLineRunner demo(EmployeeRepository employeeRepository) {
		return (args) -> {
			Employee emp1 = Employee.builder().firstName("Ram").lastName("Gurram").age(32).salary(100000.23).build();
			Employee emp2 = Employee.builder().firstName("Ram").lastName("Chelli").age(43).salary(60000).build();
			Employee emp3 = Employee.builder().firstName("Gopi").lastName("Battu").age(45).salary(1000000).build();
			Employee emp4 = Employee.builder().firstName("Ram").lastName("Srikanth").age(39).salary(60000).build();
			Employee emp5 = Employee.builder().firstName("Surendra").lastName("Sami").age(32).salary(100000.23).build();
			Employee emp6 = Employee.builder().firstName("Deeraj").lastName("Arora").age(41).salary(1000000.23).build();
			Employee emp7 = Employee.builder().firstName("Sailu").lastName("Ptr").age(31).salary(50000.23).build();
			Employee emp8 = Employee.builder().firstName("Loopa").lastName("Battu").age(32).salary(80000.23).build();
			Employee emp9 = Employee.builder().firstName("Ram").lastName("Zlam").age(33).salary(80000.23).build();

			employeeRepository.save(emp1);
			employeeRepository.save(emp2);
			employeeRepository.save(emp3);
			employeeRepository.save(emp4);
			employeeRepository.save(emp5);
			employeeRepository.save(emp6);
			employeeRepository.save(emp7);
			employeeRepository.save(emp8);
			employeeRepository.save(emp9);

			List<Employee> emps = employeeRepository.findAll();
			printEmployees(emps, "All the employees information");

			List<IEmployee> iEmps = employeeRepository.findAllEmpsViaNativeQuery();
			printIEmployees(iEmps, "All the employees information using native query");

			iEmps = employeeRepository.findAllEmpsByFirstNameViaNativeQuery("Ram");
			printIEmployees(iEmps, "All the employees with firstName 'Ram'");

		};
	}

}

 

Total project structure looks like below.

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

All the employees information
Employee [id=1, firstName=Ram, lastName=Gurram, age=32, salary=100000.23]
Employee [id=2, firstName=Ram, lastName=Chelli, age=43, salary=60000.0]
Employee [id=3, firstName=Gopi, lastName=Battu, age=45, salary=1000000.0]
Employee [id=4, firstName=Ram, lastName=Srikanth, age=39, salary=60000.0]
Employee [id=5, firstName=Surendra, lastName=Sami, age=32, salary=100000.23]
Employee [id=6, firstName=Deeraj, lastName=Arora, age=41, salary=1000000.23]
Employee [id=7, firstName=Sailu, lastName=Ptr, age=31, salary=50000.23]
Employee [id=8, firstName=Loopa, lastName=Battu, age=32, salary=80000.23]
Employee [id=9, firstName=Ram, lastName=Zlam, age=33, salary=80000.23]

All the employees information using native query
1 , Ram , Gurram
2 , Ram , Chelli
3 , Gopi , Battu
4 , Ram , Srikanth
5 , Surendra , Sami
6 , Deeraj , Arora
7 , Sailu , Ptr
8 , Loopa , Battu
9 , Ram , Zlam

All the employees with firstName 'Ram'
1 , Ram , Gurram
2 , Ram , Chelli
4 , Ram , Srikanth
9 , Ram , Zlam

You can download complete working application from below link.

https://github.com/harikrishna553/springboot/tree/master/jpa/raw-sql-projection-demo

 

 

 

 

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