Spring JDBC

package at.aydin.lab.jdbc.legacy;

import java.sql.*;
import java.util.*;

// Design Pattern: DAO
// Zweck: Kapselt Statement-, ResultSet- und Mapping-Boilerplate.
public final class CustomerDao {
    private final Connection connection;
    public CustomerDao(Connection connection) {
        this.connection = connection;
    }

    public void init() throws SQLException {
        try (Statement s = connection.createStatement()) {
            s.execute("create table if not exists customer(id bigint primary key,name varchar(100))");
        }
    }

    public void save(long id, String name) throws SQLException {
        try (PreparedStatement p = connection.prepareStatement("merge into customer key(id) values(?,?)")) {
            p.setLong(1, id);
            p.setString(2, name);
            p.executeUpdate();
        }
    }

    public Optional<String> findName(long id) throws SQLException {
        try (PreparedStatement p = connection.prepareStatement("select name from customer where id=?")) {
            p.setLong(1, id);
            try (ResultSet r = p.executeQuery()) {
                return r.next() ? Optional.of(r.getString(1)) : Optional.empty();
            }
        }
    }
}

package at.aydin.lab.jdbc.modern;

import org.springframework.jdbc.core.simple.JdbcClient;
import java.util.*;

// Design Pattern: Repository + Row Mapper
// Zweck: SQL bleibt explizit, Infrastruktur-Boilerplate wird vom JdbcClient übernommen.
public final class CustomerRepository {
    private final JdbcClient jdbc;
    public CustomerRepository(JdbcClient jdbc) {
        this.jdbc = jdbc;
    }

    public void init() {
        jdbc.sql("create table if not exists customer(id bigint primary key,name varchar(100))").update();
    }

    public void save(Customer c) {
        jdbc.sql("merge into customer key(id) values(:id,:name)").param("id", c.id()).param("name", c.name())
                .update();
    }

    public Optional<Customer> find(long id) {
        return jdbc.sql("select id,name from customer where id=:id").param("id", id).query((rs, row) -> new Customer(rs.getLong("id"),
            rs.getString("name"))).optional();
    }
}

package at.aydin.lab.jdbc.modern;

public record Customer(long id, String name) {
}