Read replicas and Spring Data Part 2: Configuring the base project

In our previous post we set up multiple PostgreSQL instances with the same data.
Our next step would be to configure our spring project by using the both servers.

As stated previously we shall use some of the code taken from the Spring Boot JPA post, since we use exactly the same database.

This shall be our gradle build file

plugins {
	id 'org.springframework.boot' version '2.1.9.RELEASE'
	id 'io.spring.dependency-management' version '1.0.8.RELEASE'
	id 'java'
}

group = 'com.gkatzioura'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
	mavenCentral()
}

dependencies {
	implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
	implementation 'org.springframework.boot:spring-boot-starter-web'
	implementation "org.postgresql:postgresql:42.2.8"
	testImplementation 'org.springframework.boot:spring-boot-starter-test'
}

Now let’s proceed on creating the model based on the table created on the previous blog.

package com.gkatzioura.springdatareadreplica.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 = "employee", catalog="spring_data_jpa_example")
public class Employee {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

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

    @Column(name = "lastname")
    private String lastname;

    @Column(name = "email")
    private String email;

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

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

    public Long getId() {
        return id;
    }

    public void setId(Long 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 String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Integer getAge() {
        return age;
    }

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

    public Integer getSalary() {
        return salary;
    }

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

}

And the next step is to create a spring data repository.

package com.gkatzioura.springdatareadreplica.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import com.gkatzioura.springdatareadreplica.entity.Employee;

public interface EmployeeRepository extends JpaRepository<Employee,Long> {
}

Also we are going to add a controller.

package com.gkatzioura.springdatareadreplica.controller;

import java.util.List;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.gkatzioura.springdatareadreplica.entity.Employee;
import com.gkatzioura.springdatareadreplica.repository.EmployeeRepository;

@RestController
public class EmployeeContoller {

    private final EmployeeRepository employeeRepository;

    public EmployeeContoller(EmployeeRepository employeeRepository) {
        this.employeeRepository = employeeRepository;
    }

    @RequestMapping("/employee")
    public List<Employee> getEmployees() {
        return employeeRepository.findAll();
    }

}

All that it takes is to just add the right properties in you application.yaml

spring:
  datasource:
    platform: postgres
    driverClassName: org.postgresql.Driver
    username: db-user
    password: your-password
    url: jdbc:postgresql://127.0.0.2:5432/postgres

Spring boot has made it possible nowadays not to bother with any JPA configurations.

This is all you need in order to run the application. Once your application is running just try to fetch the employees.

curl http://localhost:8080/employee

As you have seen we did not do any JPA configuration. Since Spring Boot 2 specifying the database url is sufficient for the auto configuration to kick in and do all this configuration for you.

However in our case we want to have multiple datasource and entity manager configurations. In the next post we shall configure the entity managers for our application.

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