Spring boot check external service status on boot - spring

Question

I want check some external http service before my Spring Boot is ready.
The url to the external web service are stored in a property file with a #ConfigurationProperties class.
How do this check i tried using a springApplication.addListner() with a ping method. But the property class have not then been initialized.
public class ApplicationStartListener implements ApplicationListener<ApplicationPreparedEvent> {
#Override
public void onApplicationEvent(ApplicationPreparedEvent event) {
String url = AppProp.getURL();
inet = InetAddress.getByName(url );
inet.isReachable(5000)
...
application.yml
tops:
http://service.com
#Component
#ConfigurationProperties("tops")
public class AppProp{
private static String url;
public static String getUrl() {

Answer 1

The easiest way to accomplish this is to implement the ApplicationRunner interface.
From the Spring Boot documentation [1]
If you need to run some specific code once the SpringApplication has started, you can implement the ApplicationRunner or CommandLineRunner interfaces. Both interfaces work in the same way and offer a single run method which will be called just before SpringApplication.run(…​) completes.
[1] https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-spring-application.html#boot-features-command-line-runner
Assuming you have url defined in application.properties:
#SpringBootApplication
public class MyApplication implements ApplicationRunner
{
#Inject
private AppConfig appConfig;
#Inject
private ConfigurableApplicationContext applicationContext;
public static void main(String[] args)
{
SpringApplication.run(MyApplication.class, args);
}
#Override
public void run(ApplicationArguments args) throws Exception
{
InetAddress inetAddress = InetAddress.getByName(appConfig.getUrl());
if (!inetAddress.isReachable(5000))
{
// Stop the application or do other things
}
}
#Component
#ConfigurationProperties
public static class AppConfig
{
private String url;
public String getUrl()
{
return url;
}
public void setUrl(String url)
{
this.url = url;
}
}
}
If you need even more control than this, you can use SpringApplicationRunListener [2]
[2] http://docs.spring.io/spring-boot/docs/current/api/org/springframework/boot/SpringApplicationRunListener.html
#SpringBootApplication
public class MyApplication implements SpringApplicationRunListener
{
public MyApplication() { }
public MyApplication(SpringApplication springApplication, String[] args) { }
public static void main(String[] args)
{
SpringApplication.run(MyApplication.class, args);
}
#Override
public void started() { }
#Override
public void environmentPrepared(ConfigurableEnvironment environment)
{
// 1st opportunity
InetAddress inetAddress = InetAddress.getByName(environment.getProperty("url"));
if (!inetAddress.isReachable(5000))
{
// Stop the application or do other things
}
}
#Override
public void contextPrepared(ConfigurableApplicationContext context)
{
// 2nd opportunity
InetAddress inetAddress = InetAddress.getByName(context.getEnvironment().getProperty("url"));
if (!inetAddress.isReachable(5000))
{
// Stop the application or do other things
}
}
#Override
public void contextLoaded(ConfigurableApplicationContext context)
{
// 3rd opportunity
InetAddress inetAddress = InetAddress.getByName(context.getEnvironment().getProperty("url"));
if (!inetAddress.isReachable(5000))
{
// Stop the application or do other things
}
}
#Override
public void finished(ConfigurableApplicationContext context, Throwable exception)
{
// 4th opportunity
InetAddress inetAddress = InetAddress.getByName(context.getEnvironment().getProperty("url"));
if (!inetAddress.isReachable(5000))
{
// Stop the application or do other things
}
}
#Component
#ConfigurationProperties
public static class AppConfig {
private String url;
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
}
}
then create META-INF\spring.factories and add
org.springframework.boot.SpringApplicationRunListener=com.foobar.MyApplication