Database

PersistentUserRepository

package task1.adapter.persistence;

import com.google.common.collect.Lists;
import task1.core.User;
import task1.core.UserRepository;

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.List;

/**
* @author Ivan Genchev ([email protected])
*/
public class PersistentUserRepository implements UserRepository {

  interface RowFetcher<T> {

    T fetchRow(ResultSet rs) throws SQLException;

  }

  @Override
  public void register(User user) {
    Connection connection = getConnection();

    PreparedStatement stmt;
    try {
      // Protects us from SQL injection
      stmt = connection.prepareStatement("insert into taskone(id, name, age, address) values(?,?,?,?)");
      stmt.setInt(1, user.id.intValue());
      stmt.setString(2, user.name);
      stmt.setInt(3, user.age);
      stmt.setString(4, user.address);

      stmt.execute();

      stmt.close();

    } catch (SQLException e) {
      e.printStackTrace();
    } finally {

      try {
        connection.close();
      } catch (SQLException e) {
        e.printStackTrace();
      }
    }
  }

  @Override
  public List<User> findAll() {
    return fetchRows("select id, name, age, address from taskone", new RowFetcher<User>() {
      @Override
      public User fetchRow(ResultSet rs) throws SQLException {
        Integer id = rs.getInt(1); // test with get long
        String name = rs.getString(2);
        Integer age = rs.getInt(3);
        String address = rs.getString(4);
        return new User(Long.valueOf(id), name, address, age);
      }
    });


  }

  private <T> List<T> fetchRows(String query, RowFetcher<T> fetcher) {
    Connection connection = getConnection();
    List<T> result = Lists.newArrayList();
    try {
      Statement stmt = connection.createStatement();
      ResultSet rs = stmt.executeQuery(query);

      while (rs.next()) {
        T rowItem = fetcher.fetchRow(rs);
        result.add(rowItem);
      }

    } catch (SQLException e) {
      e.printStackTrace();
    } finally {
      try {
        connection.close();
      } catch (SQLException e) {
        e.printStackTrace();
      }
    }
    return result;
  }

  private Connection getConnection() {
    try {

      return DriverManager.getConnection("jdbc:postgresql://localhost:5432/jdbc_tasks", "postgres", "1234");

    } catch (SQLException e) {
      e.printStackTrace();
    }

    //TODO(mgenov) we have to handle properly connection errors
    return null;
  }
}

PersistentUserRepositoryTest

package task1.adapter.persistence;

import org.junit.Before;
import org.junit.Test;
import task1.core.User;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.List;

import static org.hamcrest.Matchers.is;
import static org.junit.Assert.*;

/**
 * @author Ivan Genchev ([email protected])
 */
public class PersistentUserRepositoryTest {

  @Before
  public void cleanUp() {
    try {
      Connection connection = DriverManager.getConnection(
              "jdbc:postgresql://localhost:5432/jdbc_tasks", "postgres", "1234"
      );
      connection.createStatement().executeUpdate("truncate taskone");
      connection.close();
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }


  @Test
  public void getWhatWasPut() throws Exception {
    PersistentUserRepository repository = new PersistentUserRepository();

    User user = new User(1l, "Stefan", "my street", 23);
    repository.register(user);

    List<User> users = repository.findAll();

    assertThat(users.size(), is(1));
    assertThat(users.get(0).id,is(1l));
    assertThat(users.get(0).name,is("Stefan"));
  }
}

User

package task1.core;

/**
* @author Ivan Genchev ([email protected])
*/
public class User {
  public final Long id;
  public final String name;
  public final String address;
  public final Integer age;

  public User(Long id, String name, String address, Integer age) {
    this.id = id;
    this.name = name;
    this.address = address;
    this.age = age;
  }
}

UserRepository

package task1.core;

import java.util.List;

/**
* @author Ivan Genchev ([email protected])
*/
public interface UserRepository {

  void register(User user);

  List<User> findAll();

}