Spring ve JDBC ile Relational Data ya erişmek

(Kaynak: https://spring.io/guides/gs/relational-data-access/)

1. Bir müşteri yani Customer classı yaratalım (pojo):

package hello;

public class Customer {
    private long id;
    private String firstName, lastName;

    public Customer(long id, String firstName, String lastName) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    }

    @Override
    public String toString() {
        return String.format(
                "Customer[id=%d, firstName='%s', lastName='%s']",
                id, firstName, lastName);
    }

    // getter & setterları buraya ekleyin
}

2. Veriyi depolamak ve çağırmak için Application.java yazıyoruz:

package hello;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;

@SpringBootApplication
public class Application implements CommandLineRunner {

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

    @Autowired
    JdbcTemplate jdbcTemplate;

    @Override
    public void run(String... strings) throws Exception {
        System.out.println("Creating tables");
        jdbcTemplate.execute("drop table customers if exists");
        jdbcTemplate.execute("create table customers(" +
                "id serial, first_name varchar(255), last_name varchar(255))");

        String[] fullNames = new String[]{"John Woo", "Jeff Dean", "Josh Bloch", "Josh Long"};
        for (String fullname : fullNames) {
            String[] name = fullname.split(" ");
            System.out.printf("Inserting customer record for %s %s\n", name[0], name[1]);
            jdbcTemplate.update(
                    "INSERT INTO customers(first_name,last_name) values(?,?)",
                    name[0], name[1]);
        }

        System.out.println("Querying for customer records where first_name = 'Josh':");
        List<Customer> results = jdbcTemplate.query(
                "select id, first_name, last_name from customers where first_name = ?", new Object[] { "Josh" },
                new RowMapper<Customer>() {
                    @Override
                    public Customer mapRow(ResultSet rs, int rowNum) throws SQLException {
                        return new Customer(rs.getLong("id"), rs.getString("first_name"),
                                rs.getString("last_name"));
                    }
                });

        for (Customer customer : results) {
            System.out.println(customer);
        }
    }
}

3. Build ve run ediyoruz:

Gradle : ./gradlew bootRun
Maven : mvn spring-boot:run
Gördüğümüz çıktı şöyle oluyor:

Creating tables
Inserting customer record for John Woo
Inserting customer record for Jeff Dean
Inserting customer record for Josh Bloch
Inserting customer record for Josh Long
Querying for customer records where first_name = 'Josh':
Customer[id=3, firstName='Josh', lastName='Bloch']
Customer[id=4, firstName='Josh', lastName='Long']

Böylece Spring ile basit bir JDBC client yazmış olduk.