1.Create springboot project using https://start.spring.io/
2.Add dependency , Spring Web, Mysql Driver, Spring JPA
3. Generate the code and , import as existing maven project
4.Since this is simple database sample add DBconnection details to the application.properties file
spring.datasource.url=jdbc:mysql://db_ip:3306/db_name?useSSL=false&serverTimezone=UTC
spring.datasource.username=user_name
spring.datasource.password=password
5.Next we create 3 layers virtually for easy understand and development
1.Control Layer
2.Service Layer
3.Repository Layer
6.Create Entity class for relevant table to be used,name City
import java.util.Objects;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name = "cities_test") // Mapping table with DB
public class City {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
private int population;
public City() {
}
public City(Long id, String name, int population) {
this.id = id;
this.name = name;
this.population = population;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getPopulation() {
return population;
}
public void setPopulation(int population) {
this.population = population;
}
}
7.Extend CrudRepository and create CityRepository interface for doing db related transactions
Make sure to add @Repository annotation to the class
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
@Repository
public interface CityRepository extends CrudRepository<City, Long>{
}
8.Then create and CityService interface for doing transaction with Repository
also add signature for retrieve data from db layer
import java.util.List;
import lk.inova.example.all_demo.repository.City;
public interface CityService {
List<City> findAllCities();
}
9.Then Create impl class by implementing above CityService interface method, also Autowired the CityRepository interface to service Impl class, make sure to set @Service annotation
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import lk.inova.example.all_demo.repository.City;
import lk.inova.example.all_demo.repository.CityRepository;
import lk.inova.example.all_demo.service.CityService;
@Service
public class CityServiceImpl implements CityService {
@Autowired
CityRepository repository;
@Override
public List<City> findAllCities() {
return (List<City>) repository.findAll();
}
}
10.Then create class MyCityConroller for any transaction about cities - Get Cities, Update, Delete..etc
makesure to add annotation @RestController,...Also Add request mapping and GetMapping to relevant method. also Autowired CityServiceImple class.
@RestController
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import lk.inova.example.all_demo.repository.City;
import lk.inova.example.all_demo.service.impl.CityServiceImpl;
@RestController
@RequestMapping("/db")
public class MyCityController {
@Autowired
CityServiceImpl cityServiceImpl;
@GetMapping("/cities")
public List<City> getAllCities(){
return cityServiceImpl.findAllCities();
}
}
11.Now you can see the all cities
http://localhost:8080/db/cities
note :
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.5.4</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>lk.inova.example</groupId>
<artifactId>all_demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>all_demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
