Persistenz

<?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>at.aydin.academy</groupId>
        <artifactId>04persistence-pair</artifactId>
        <version>1.0.0</version>
        <relativePath>../pom.xml</relativePath>
    </parent>
    <artifactId>persistence-legacy</artifactId>
    <packaging>jar</packaging>
    <name>Persistence Legacy (JDBC)</name>
    <dependencies>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
            </plugin>

        </plugins>
    </build>
</project>

package at.aydin.lab.persistence.legacy;

public final class PersistenceLegacyApplication {
    private PersistenceLegacyApplication() {
    }

    public static void main(String[] args) {
        CustomerDao dao = new JdbcCustomerDao("jdbc:h2:mem:legacy;DB_CLOSE_DELAY=-1");
        dao.save("Aydin Polat", "aydin@example.test");
        dao.findAll().forEach(System.out::println);
    }
}

package at.aydin.lab.persistence.legacy;

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

package at.aydin.lab.persistence.legacy;

import java.util.List;

// Design Pattern: DAO
// Zweck: SQL und JDBC werden hinter einer fachlichen Schnittstelle gekapselt.
public interface CustomerDao {
    Customer save(String name, String email);
    List<Customer> findAll();
}

package at.aydin.lab.persistence.legacy;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public final class JdbcCustomerDao implements CustomerDao {
    private final String url;

    public JdbcCustomerDao(String url) {
        this.url = url;
        initialize();
    }

    private Connection connection() throws SQLException {
        return DriverManager.getConnection(url, "sa", "");
    }

    private void initialize() {
        String sql = "create table if not exists customer("
                + "id bigint generated by default as identity primary key, "
                + "name varchar(120), email varchar(180))";

        try (Connection connection = connection();
                Statement statement = connection.createStatement()) {
            statement.executeUpdate(sql);
        } catch (SQLException exception) {
            throw new IllegalStateException("Schema konnte nicht erstellt werden", exception);
        }
    }

    @Override
    public Customer save(String name, String email) {
        String sql = "insert into customer(name,email) values (?,?)";
        try (Connection connection = connection();
                PreparedStatement statement = connection.prepareStatement(
                        sql, Statement.RETURN_GENERATED_KEYS)) {
            statement.setString(1, name);
            statement.setString(2, email);
            statement.executeUpdate();

            try (ResultSet keys = statement.getGeneratedKeys()) {
                if (!keys.next()) {
                    throw new SQLException("Keine ID erhalten");
                }
                return new Customer(keys.getLong(1), name, email);
            }
        } catch (SQLException exception) {
            throw new IllegalStateException("Kunde konnte nicht gespeichert werden", exception);
        }
    }

    @Override
    public List<Customer> findAll() {
        List<Customer> result = new ArrayList<>();
        String sql = "select id,name,email from customer order by id";

        try (Connection connection = connection();
                Statement statement = connection.createStatement();
                ResultSet resultSet = statement.executeQuery(sql)) {
            while (resultSet.next()) {
                result.add(new Customer(
                        resultSet.getLong("id"),
                        resultSet.getString("name"),
                        resultSet.getString("email")));
            }
            return result;
        } catch (SQLException exception) {
            throw new IllegalStateException("Kunden konnten nicht gelesen werden", exception);
        }
    }
}

package at.aydin.lab.persistence.legacy;

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

class JdbcCustomerDaoTest {
    @Test
    void persistsCustomer() {
        CustomerDao dao = new JdbcCustomerDao("jdbc:h2:mem:testlegacy;DB_CLOSE_DELAY=-1");
        dao.save("Test", "test@example.test");
        assertEquals(1, dao.findAll().size());
    }
}