Create the project and business logic
Table of contents
Set up the project
Create a Java project with Maven and add the required dependencies:
<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:
package com.testcontainers.demo;
public record Customer(Long id, String name) {}Create a CustomerService class with methods to create, retrieve, and delete
customers:
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);
}
}
}