Environment: Java 21, Spring Boot 3.2.1, PostgreSQL 16, maven 3.9.6 on macOS Catalina 10.15.7
The Scenario
The Database is PostgreSQL and we want to run a simple query to make sure that the database connection looks good once the application starts up.
One way to achieve this
One way to achieve this is to execute a simple query after the application starts up. Spring Boot's CommandLineRunner or ApplicationRunner can be leveraged to do this. This is a good place to run specific code after the application has started.
Here is a code snippet for this:
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.jdbc.core.simple.JdbcClient;
@SpringBootApplication
@Slf4j
public class MyApplication {
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
@Autowired(required = false)
JdbcClient jdbcClient;
@Bean
public CommandLineRunner commandLineRunner() {
return args -> {
if (jdbcClient != null) {
log.info("Database check: {}", jdbcClient.sql("SELECT version()").query(String.class).single());
}
};
}
}
The above highlighted is the code snippet that gets executed after the application gets started. It just logs the executed query result, nothing but the database version.
An integration test case can also be put in place as shown below, which makes sure that the database connection and version look good. This kind of testcase is good to have to make sure that the code is tested against the same db version as the production.
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.jdbc.AutoConfigureTestDatabase;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.context.annotation.Import;
import org.springframework.jdbc.core.simple.JdbcClient;
import org.springframework.test.context.ActiveProfiles;
import static org.assertj.core.api.Assertions.*;
/**
* An integration test to check Database connectivity.
*/
@ActiveProfiles("test")
// We don't want the H2 in-memory database.
// We will provide a custom 'test container' as DataSource, so don't replace it.
@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
@DataJpaTest
@Import(TestContainersConfiguration.class)
public class DatabaseCheckIT {
@Autowired
JdbcClient jdbcClient;
@Test
void database_connection_works_and_version_looks_good() {
assertThat(jdbcClient.sql("SELECT version()").query(String.class).single())
.contains("16.0");
}
}
The above test case uses Testcontainers and a test configuration as shown below for unit/integration tests:
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.test.context.TestConfiguration;
import org.springframework.boot.testcontainers.service.connection.ServiceConnection;
import org.springframework.context.annotation.Bean;
import org.testcontainers.containers.PostgreSQLContainer;
/**
* Test Configuration for testcontainers.
*/
@TestConfiguration(proxyBeanMethods = false)
@Slf4j
public class TestContainersConfiguration {
private static final String POSTGRES_IMAGE_TAG = "postgres:16.0";
@Bean
@ServiceConnection
PostgreSQLContainer postgreSQLContainer() {
return new PostgreSQLContainer<>(POSTGRES_IMAGE_TAG)
.withDatabaseName("my-application")
.withUsername("my-application")
.withPassword("s3cr3t")
.withReuse(true);
}
}
⚠ Gotcha
Note that in the main application class, for JdbcClient @Autowired annotation, the optional property required is explicitly set to false. The reason for this is if there are any integration test cases to test specific layers (test slices like @GraphQlTest) that do not auto configure datasource, when the application class is run as part of starting Spring Boot run, the testcase runs into exception as JdbcClient bean is not available for auto wiring. So, in those cases jdbcClient property would be null. So, a non null check is required to safely run the SQL statement.
💡 TIPS
The CommandLineRunner bean in the application class can conditionally be defined on some DataSource related bean/class by annotation it with @ConditionalOnBean or @ConditionalOnClass. I couldn't find a way to get it conditionally defined and be working for all scenarios.
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