I want to run code after my spring-boot app starts to monitor a directory for changes.
I have tried running a new thread but the @Autowired services have not been set at that point.
I have been able to find ApplicationPreparedEvent, which fires before the @Autowired annotations are set. Ideally I would like the event to fire once the application is ready to process http requests.
Is there a better event to use, or a better way of running code after the application is live in spring-boot?
Try:
@Configuration
@EnableAutoConfiguration
@ComponentScan
public class Application extends SpringBootServletInitializer {
@SuppressWarnings("resource")
public static void main(final String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(Application.class, args);
context.getBean(Table.class).fillWithTestdata(); // <-- here
}
}
Have you tried ApplicationReadyEvent?
@Component
public class ApplicationStartup
implements ApplicationListener<ApplicationReadyEvent> {
/**
* This event is executed as late as conceivably possible to indicate that
* the application is ready to service requests.
*/
@Override
public void onApplicationEvent(final ApplicationReadyEvent event) {
// here your code ...
return;
}
}
Code from: http://blog.netgloo.com/2014/11/13/run-code-at-spring-boot-startup/
This is what the documentation mentions about the startup events:
...
Application events are sent in the following order, as your application runs:
An ApplicationStartedEvent is sent at the start of a run, but before any processing except the registration of listeners and initializers.
An ApplicationEnvironmentPreparedEvent is sent when the Environment to be used in the context is known, but before the context is created.
An ApplicationPreparedEvent is sent just before the refresh is started, but after bean definitions have been loaded.
An ApplicationReadyEvent is sent after the refresh and any related callbacks have been processed to indicate the application is ready to service requests.
An ApplicationFailedEvent is sent if there is an exception on startup.
...
Why not just create a bean that starts your monitor on initialization, something like:
@Component
public class Monitor {
@Autowired private SomeService service
@PostConstruct
public void init(){
// start your monitoring in here
}
}
the init method will not be called until any autowiring is done for the bean.
You can extend a class using ApplicationRunner , override the run() method and add the code there.
import org.springframework.boot.ApplicationRunner;
@Component
public class ServerInitializer implements ApplicationRunner {
@Override
public void run(ApplicationArguments applicationArguments) throws Exception {
//code goes here
}
}
ApplicationReadyEvent is really only useful if the task you want to perform is not a requirement for correct server operation. Starting an async task to monitor something for changes is a good example.
If, however your server is in a 'not ready' state until the task is completed then it's better to implement SmartInitializingSingleton because you'll get the callback before your REST port has been opened and your server is open for business.
Don't be tempted to use @PostConstruct for tasks that should only happen once ever. You'll get a rude surprise when you notice it being called multiple times...
With spring configuration :
@Configuration
public class ProjectConfiguration {
private static final Logger log =
LoggerFactory.getLogger(ProjectConfiguration.class);
@EventListener(ApplicationReadyEvent.class)
public void doSomethingAfterStartup() {
log.info("hello world, I have just started up");
}
}
Best way to execute block of code after Spring Boot application started is using PostConstruct annotation.Or also you can use command line runner for the same.
1. Using PostConstruct annotation
@Configuration
public class InitialDataConfiguration {
@PostConstruct
public void postConstruct() {
System.out.println("Started after Spring boot application !");
}
}
2. Using command line runner bean
@Configuration
public class InitialDataConfiguration {
@Bean
CommandLineRunner runner() {
return args -> {
System.out.println("CommandLineRunner running in the UnsplashApplication class...");
};
}
}
I really like the suggestion for usage of the EventListener annotation by @cahen (https://stackoverflow.com/a/44923402/9122660) since it is very clean. Unfortunately I could not get this to work in a Spring + Kotlin setup. What does work for Kotlin is adding the class as a method parameter:
@EventListener
fun doSomethingAfterStartup(event: ApplicationReadyEvent) {
System.out.println("hello world, I have just started up");
}
Providing an example for Dave Syer answer, which worked like a charm:
@Component
public class CommandLineAppStartupRunner implements CommandLineRunner {
private static final Logger logger = LoggerFactory.getLogger(CommandLineAppStartupRunner.class);
@Override
public void run(String...args) throws Exception {
logger.info("Application started with command-line arguments: {} . \n To kill this application, press Ctrl + C.", Arrays.toString(args));
}
}
You have several choices:
Using CommandLineRunner or ApplicationRunner as a Bean definition:
Spring Boot executes these towards the end of the application startup process. In most circumstances, the CommandLineRunner will do the job. Following is an example of a CommandLineRunner implementation with Java 8:
@Bean
public CommandLineRunner commandLineRunner() {
return (args) -> System.out.println("Hello World");
}
Note that the args is the String array of arguments. You can also provide an implementation of this interface and define it as a Spring Component:
@Component
public class MyCommandLineRunner implements CommandLineRunner {
@Override
public void run(String... args) throws Exception {
System.out.println("Hello World");
}
}
You can use the ApplicationRunner if you need better argument management. ApplicationRunner takes an ApplicationArguments instance that has enhanced argument management options.
You can also order the CommandLineRunner and ApplicationRunner beans using Spring's @Order annotation:
@Bean
@Order(1)
public CommandLineRunner commandLineRunner() {
return (args) -> System.out.println("Hello World, Order 1");
}
@Bean
@Order(2)
public CommandLineRunner commandLineRunner() {
return (args) -> System.out.println("Hello World, Order 2");
}
Using Spring Boot's ContextRefreshedEvent:
Spring Boot publishes several events at startup. These events indicate the completion of a phase in the application startup process. You can listen to the ContextRefreshedEvent and execute custom code:
@EventListener(ContextRefreshedEvent.class)
public void execute() {
if(alreadyDone) {
return;
}
System.out.println("hello world");
}
ContextRefreshedEvent is published several times. Thus, ensure to put a check whether the code execution is already finished.
