Spring boot loads lots of beans internally to run the application with minimal configuration. In this example, we will learn to find out all those loaded beans by Spring Boot and their class type information.
Using ApplicationContext to get all loaded beans
To execute a method automatically, when the application is fully loaded, I am using CommandLineRunner interface. CommandLineRunner is used to indicate that a bean should run when it is contained within a Spring Application.
- Use
ApplicationContext.getBeanDefinitionNames()to find the name of all loaded beans - Use
ApplicationContext.getBean(beanName)to get bean including its runtime type information.
import java.util.Arrays; 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.boot.builder.SpringApplicationBuilder; import org.springframework.boot.web.support.SpringBootServletInitializer; import org.springframework.context.ApplicationContext; @SpringBootApplication public class SpringBootWebApplication extends SpringBootServletInitializer implements CommandLineRunner { @Override protected SpringApplicationBuilder configure(SpringApplicationBuilder application) { return application.sources(SpringBootWebApplication.class); } public static void main(String[] args) throws Exception { SpringApplication.run(SpringBootWebApplication.class, args); } @Autowired private ApplicationContext appContext; @Override public void run(String... args) throws Exception { String[] beans = appContext.getBeanDefinitionNames(); Arrays.sort(beans); for (String bean : beans) { System.out.println(bean + " of Type :: " + appContext.getBean(bean).getClass()); } } }Program Output
Running the above application will print bean names and type information in the console like the below:
2017-03-06 13:22:50 - Tomcat started on port(s): 8080 (http) basicErrorController of Type :: class org.springframework.boot.autoconfigure.web.BasicErrorController beanNameHandlerMapping of Type :: class org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping beanNameViewResolver of Type :: class org.springframework.web.servlet.view.BeanNameViewResolver characterEncodingFilter of Type :: class org.springframework.boot.web.filter.OrderedCharacterEncodingFilter conventionErrorViewResolver of Type :: class org.springframework.boot.autoconfigure.web.DefaultErrorViewResolver defaultServletHandlerMapping of Type :: class org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport$EmptyHandlerMapping defaultViewResolver of Type :: class org.springframework.web.servlet.view.InternalResourceViewResolver dispatcherServlet of Type :: class org.springframework.web.servlet.DispatcherServlet dispatcherServletRegistration of Type :: class org.springframework.boot.web.servlet.ServletRegistrationBean duplicateServerPropertiesDetector of Type :: class org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration$DuplicateServerPropertiesDetector embeddedServletContainerCustomizerBeanPostProcessor of Type :: class org.springframework.boot.context.embedded.EmbeddedServletContainerCustomizerBeanPostProcessor error of Type :: class org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$SpelView errorAttributes of Type :: class org.springframework.boot.autoconfigure.web.DefaultErrorAttributes ... ... ...I have truncated the output. You can verify the whole list yourself.
Happy Learning !!
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