---
title: Create the project and business logic
linkTitle: Create the project
description: Set up a Java project with a PostgreSQL-backed customer service for lifecycle testing.
weight: 10
---

## Set up the project

Create a Java project with Maven and add the required dependencies:

```xml
<dependencies>
    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <version>42.7.3</version>
    </dependency>
    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>1.5.6</version>
    </dependency>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter</artifactId>
        <version>5.10.2</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.testcontainers</groupId>
        <artifactId>testcontainers-junit-jupiter</artifactId>
        <version>2.0.4</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.testcontainers</groupId>
        <artifactId>testcontainers-postgresql</artifactId>
        <version>2.0.4</version>
        <scope>test</scope>
    </dependency>
</dependencies>
```

## Create the business logic

Create a `Customer` record:

```java
package com.testcontainers.demo;

public record Customer(Long id, String name) {}
```

Create a `CustomerService` class with methods to create, retrieve, and delete
customers:

```java
package com.testcontainers.demo;

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

public class CustomerService {

  private final String url;
  private final String username;
  private final String password;

  public CustomerService(String url, String username, String password) {
    this.url = url;
    this.username = username;
    this.password = password;
    createCustomersTableIfNotExists();
  }

  public void createCustomer(Customer customer) {
    try (Connection conn = this.getConnection()) {
      PreparedStatement pstmt = conn.prepareStatement(
        "insert into customers(id,name) values(?,?)"
      );
      pstmt.setLong(1, customer.id());
      pstmt.setString(2, customer.name());
      pstmt.execute();
    } catch (SQLException e) {
      throw new RuntimeException(e);
    }
  }

  public List<Customer> getAllCustomers() {
    List<Customer> customers = new ArrayList<>();
    try (Connection conn = this.getConnection()) {
      PreparedStatement pstmt = conn.prepareStatement(
        "select id,name from customers"
      );
      ResultSet rs = pstmt.executeQuery();
      while (rs.next()) {
        long id = rs.getLong("id");
        String name = rs.getString("name");
        customers.add(new Customer(id, name));
      }
    } catch (SQLException e) {
      throw new RuntimeException(e);
    }
    return customers;
  }

  public Optional<Customer> getCustomer(Long customerId) {
    try (Connection conn = this.getConnection()) {
      PreparedStatement pstmt = conn.prepareStatement(
        "select id,name from customers where id = ?"
      );
      pstmt.setLong(1, customerId);
      ResultSet rs = pstmt.executeQuery();
      if (rs.next()) {
        long id = rs.getLong("id");
        String name = rs.getString("name");
        return Optional.of(new Customer(id, name));
      }
    } catch (SQLException e) {
      throw new RuntimeException(e);
    }
    return Optional.empty();
  }

  public void deleteAllCustomers() {
    try (Connection conn = this.getConnection()) {
      PreparedStatement pstmt = conn.prepareStatement("delete from customers");
      pstmt.execute();
    } catch (SQLException e) {
      throw new RuntimeException(e);
    }
  }

  private void createCustomersTableIfNotExists() {
    try (Connection conn = this.getConnection()) {
      PreparedStatement pstmt = conn.prepareStatement(
        """
        create table if not exists customers (
            id bigint not null,
            name varchar not null,
            primary key (id)
        )
        """
      );
      pstmt.execute();
    } catch (SQLException e) {
      throw new RuntimeException(e);
    }
  }

  private Connection getConnection() {
    try {
      return DriverManager.getConnection(url, username, password);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }
}
```