have have these two apps which actually do the same (if I am correct)
#SpringBootApplication
public class DemoApplication {
#Autowired
HelloWorld helloWorld;
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
#Bean
public CommandLineRunner run() {
helloWorld.setMessage("wow");
return (load) -> {
helloWorld.getMessage();
};
}
}
and
public class MainApp {
public static void main(String[] args) {
ApplicationContext context = new
ClassPathXmlApplicationContext("Beans.xml");
HelloWorld obj = (HelloWorld) context.getBean("helloWorld");
obj.getMessage();
}
}
both uses
#Component
public class HelloWorld {
private String message;
public void setMessage(String message) {
this.message = message;
}
public void getMessage() {
System.out.println("Your Message : " + message);
}
}
The only difference at the helloWord obj is, that if I use the MainApp-class in my program, then the helloWorld class doesn't need the #Component annotation.
My Question:
If I am correct the SpringBoot annotation makes it unnecessary to define a ClassPathXMLApplicationContext. #Autowire does that for me.
I am now interested if I AutoWire lets say 100 objects at the beginning, all these objects are now in the IoC container correct?
If so: Is not possible to just hand out that container in a CTOR of another class and have access to all saved objects there like:
(HelloWorld) context.getBean("helloWorld"); or
(someRandomClass) context.getBean("someRandomClass")
public CTOR(IOCContainer container) {
this.container = container;
}
Instead of that implementation
public CTOR(HelloWorld helloWorld, SomeRandomClass someRandomClass) {
this.helloWorld = helloWorld;
this.someRandomClass = someRandomClass;
}
And if that is possible, how can I do that?
(There is no use case/task behind my question, i am just interested if that is possible)
The XML'ish way of configuration where you define your bean and wiring via
<bean ... etc. pp.
can be completely replaced by either using
#Component
public class MyClass ....
or by
#Bean
public MyClass myClass() {return new MyClass();}
definition in a configuration class. Both ways place the entity in the IoC container of Spring.
The #Autowire just informs the IoC container of Spring that you would like to have a bean fulfilling the contract of the entity marked with #Autowire injected into this place.
In order to get access to the container you just need to inject the ApplicationContext where you would like to have it.
There are two ways of creating beans in Spring. One is through XML config and the other is through annotation config. Annotation config is the preferred approach as it has lot of advantages over xml config.
Spring boot doesnt have any thing to do with annotation or xml config. Its just a easy way to boot spring application. #Component creates the object of the annotated bean in the application context. #Import or #ImportResource are the annotations used to load the configs from Annotations or through XML configs in Spring boot. With Spring boot u need not create ClassPathXMlCOntext or AnnotationContext objects, but its created internally by spring boot.
#Autowired is a way of getting the beans into any object by injecting rather than tight coupling to the code. Spring container(Application context) do this job of injecting. Just autowiring any class wont create the objects in Spring context. Its just an indication for the Spring context to set the object in the Application context here. You need to create them explicitly inside a xml config/ or annotations like #Component #Service others.
There is no need of hand out of container anywhere. U can just #Autowire ApplicationContext context; in any other spring bean object. With which you can call getBean(YourBean.class) to get that bean.
How can I get to know names of all the beans that are loaded as part of my spring boot app? I would like have some code in main method to print the details of beans that are loaded once the server is started up.
As shown in the getting started guide of spring-boot: https://spring.io/guides/gs/spring-boot/
#SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
#Bean
public CommandLineRunner commandLineRunner(ApplicationContext ctx) {
return args -> {
System.out.println("Let's inspect the beans provided by Spring Boot:");
String[] beanNames = ctx.getBeanDefinitionNames();
Arrays.sort(beanNames);
for (String beanName : beanNames) {
System.out.println(beanName);
}
};
}
}
As #Velu mentioned in the comments, this will not list manually registered beans.
In case you want to do so, you can use getSingletonNames(). But be careful. This method only returns already instantiated beans. If a bean isn't already instantiated, it will not be returned by getSingletonNames().
May I suggest using Actuator? it provides several endpoints including /beans which lists all beans in the application. You say "once the server is started" so this is an option for web applications.
To set up actuator
https://spring.io/guides/gs/actuator-service/
List of endpoints in actuator
http://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-endpoints.html
Well, Although, this question is already answered, I still want to provide an answer which is a Java 8 variant :)
Arrays.asList(context.getBeanDefinitionNames()).stream().sorted().forEach(System.out::println);
Lets do Java 8 !!!
Actually I would recommend to create this class aside from modifying your #SpringBootApplication.
#Component
public class ContextTeller implements CommandLineRunner {
#Autowired
ApplicationContext applicationContext;
#Override
public void run(String... args) throws Exception {
System.out.println("-------------> just checking!");
System.out.println(Arrays.asList(applicationContext.getBeanDefinitionNames()));
}}
This way Spring Boot will load this class and execute just after loading context. Then you just can remove the file, and everything is clear.
applicationContext.getBeanDefinitionNames() does not show the beans which are registered without BeanDefinition instance.
For spring boot web applications, all the beans can be listed using the below endpoint.
#RestController
#RequestMapping("/list")
class ExportController {
#Autowired
private ApplicationContext applicationContext;
#GetMapping("/beans")
#ResponseStatus(value = HttpStatus.OK)
String[] registeredBeans() {
return printBeans();
}
private String[] printBeans() {
AutowireCapableBeanFactory autowireCapableBeanFactory = applicationContext.getAutowireCapableBeanFactory();
if (autowireCapableBeanFactory instanceof SingletonBeanRegistry) {
String[] singletonNames = ((SingletonBeanRegistry) autowireCapableBeanFactory).getSingletonNames();
for (String singleton : singletonNames) {
System.out.println(singleton);
}
return singletonNames;
}
return null;
}
}
[
"autoConfigurationReport",
"springApplicationArguments",
"springBootBanner",
"springBootLoggingSystem",
"environment",
"systemProperties",
"systemEnvironment",
"org.springframework.context.annotation.internalConfigurationAnnotationProcessor",
"org.springframework.boot.autoconfigure.internalCachingMetadataReaderFactory",
"org.springframework.boot.autoconfigure.condition.BeanTypeRegistry",
"org.springframework.context.annotation.ConfigurationClassPostProcessor.importRegistry",
"propertySourcesPlaceholderConfigurer",
"org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor.store",
"preserveErrorControllerTargetClassPostProcessor",
"org.springframework.context.annotation.internalAutowiredAnnotationProcessor",
"org.springframework.context.annotation.internalRequiredAnnotationProcessor",
"org.springframework.context.annotation.internalCommonAnnotationProcessor",
"org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor",
"org.springframework.scheduling.annotation.ProxyAsyncConfiguration",
"org.springframework.context.annotation.internalAsyncAnnotationProcessor",
"methodValidationPostProcessor",
"embeddedServletContainerCustomizerBeanPostProcessor",
"errorPageRegistrarBeanPostProcessor",
"messageSource",
"applicationEventMulticaster",
"org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration$EmbeddedTomcat",
"tomcatEmbeddedServletContainerFactory",
"org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration$TomcatWebSocketConfiguration",
"websocketContainerCustomizer",
"spring.http.encoding-org.springframework.boot.autoconfigure.web.HttpEncodingProperties",
"org.springframework.boot.autoconfigure.web.HttpEncodingAutoConfiguration",
"localeCharsetMappingsCustomizer",
"org.springframework.boot.autoconfigure.web.ServerPropertiesAutoConfiguration",
"serverProperties",
"duplicateServerPropertiesDetector",
"spring.resources-org.springframework.boot.autoconfigure.web.ResourceProperties",
"org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$DefaultErrorViewResolverConfiguration",
"conventionErrorViewResolver",
"org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration",
"errorPageCustomizer",
"servletContext",
"contextParameters",
"contextAttributes",
"spring.mvc-org.springframework.boot.autoconfigure.web.WebMvcProperties",
"spring.http.multipart-org.springframework.boot.autoconfigure.web.MultipartProperties",
"org.springframework.boot.autoconfigure.web.MultipartAutoConfiguration",
"multipartConfigElement",
"org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration$DispatcherServletRegistrationConfiguration",
"org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration$DispatcherServletConfiguration",
"dispatcherServlet",
"dispatcherServletRegistration",
"requestContextFilter",
"org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration",
"hiddenHttpMethodFilter",
"httpPutFormContentFilter",
"characterEncodingFilter",
"org.springframework.context.event.internalEventListenerProcessor",
"org.springframework.context.event.internalEventListenerFactory",
"reportGeneratorApplication",
"exportController",
"exportService",
"org.springframework.boot.autoconfigure.AutoConfigurationPackages",
"org.springframework.boot.autoconfigure.context.PropertyPlaceholderAutoConfiguration",
"org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$Jackson2ObjectMapperBuilderCustomizerConfiguration",
"spring.jackson-org.springframework.boot.autoconfigure.jackson.JacksonProperties",
"standardJacksonObjectMapperBuilderCustomizer",
"org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$JacksonObjectMapperBuilderConfiguration",
"org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration",
"jsonComponentModule",
"jacksonObjectMapperBuilder",
"org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration$JacksonObjectMapperConfiguration",
"jacksonObjectMapper",
"org.springframework.boot.autoconfigure.websocket.WebSocketAutoConfiguration",
"org.springframework.boot.autoconfigure.web.EmbeddedServletContainerAutoConfiguration",
"org.springframework.boot.autoconfigure.web.DispatcherServletAutoConfiguration",
"org.springframework.boot.autoconfigure.validation.ValidationAutoConfiguration",
"defaultValidator",
"org.springframework.boot.autoconfigure.web.ErrorMvcAutoConfiguration$WhitelabelErrorViewConfiguration",
"error",
"beanNameViewResolver",
"errorAttributes",
"basicErrorController",
"org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$EnableWebMvcConfiguration",
"org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter",
"mvcContentNegotiationManager",
"org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration$StringHttpMessageConverterConfiguration",
"stringHttpMessageConverter",
"org.springframework.boot.autoconfigure.web.JacksonHttpMessageConvertersConfiguration$MappingJackson2HttpMessageConverterConfiguration",
"mappingJackson2HttpMessageConverter",
"org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration",
"messageConverters",
"mvcConversionService",
"mvcValidator",
"requestMappingHandlerAdapter",
"mvcResourceUrlProvider",
"requestMappingHandlerMapping",
"mvcPathMatcher",
"mvcUrlPathHelper",
"viewControllerHandlerMapping",
"beanNameHandlerMapping",
"resourceHandlerMapping",
"defaultServletHandlerMapping",
"mvcUriComponentsContributor",
"httpRequestHandlerAdapter",
"simpleControllerHandlerAdapter",
"handlerExceptionResolver",
"mvcViewResolver",
"org.springframework.boot.autoconfigure.web.WebMvcAutoConfiguration$WebMvcAutoConfigurationAdapter$FaviconConfiguration",
"faviconRequestHandler",
"faviconHandlerMapping",
"defaultViewResolver",
"viewResolver",
"welcomePageHandlerMapping",
"org.springframework.boot.autoconfigure.jmx.JmxAutoConfiguration",
"objectNamingStrategy",
"mbeanServer",
"mbeanExporter",
"org.springframework.boot.autoconfigure.admin.SpringApplicationAdminJmxAutoConfiguration",
"springApplicationAdminRegistrar",
"org.springframework.boot.autoconfigure.context.ConfigurationPropertiesAutoConfiguration",
"org.springframework.boot.autoconfigure.web.JacksonHttpMessageConvertersConfiguration",
"spring.info-org.springframework.boot.autoconfigure.info.ProjectInfoProperties",
"org.springframework.boot.autoconfigure.info.ProjectInfoAutoConfiguration",
"multipartResolver",
"org.springframework.boot.autoconfigure.web.WebClientAutoConfiguration$RestTemplateConfiguration",
"restTemplateBuilder",
"org.springframework.boot.autoconfigure.web.WebClientAutoConfiguration",
"spring.devtools-org.springframework.boot.devtools.autoconfigure.DevToolsProperties",
"org.springframework.boot.devtools.autoconfigure.LocalDevToolsAutoConfiguration$RestartConfiguration",
"fileSystemWatcherFactory",
"classPathRestartStrategy",
"classPathFileSystemWatcher",
"hateoasObjenesisCacheDisabler",
"org.springframework.boot.devtools.autoconfigure.LocalDevToolsAutoConfiguration$LiveReloadConfiguration$LiveReloadServerConfiguration",
"org.springframework.boot.devtools.autoconfigure.LocalDevToolsAutoConfiguration$LiveReloadConfiguration",
"optionalLiveReloadServer",
"org.springframework.boot.devtools.autoconfigure.LocalDevToolsAutoConfiguration",
"lifecycleProcessor"
]
As you can see in the output, environment, systemProperties, systemEnvironment beans will not be shown using context.getBeanDefinitionNames() method.
#Component
public class ContextTeller implements CommandLineRunner {
#Autowired
public ApplicationContext applicationContext;
#Override
public void run(String... args) throws Exception {
System.out.println("<------------- Beans loaded --------------->");
Arrays.asList(applicationContext.getBeanDefinitionNames()).stream().forEach(System.out::println);
}
}
As mentioned by #Zergleb, using Actuator is appropriate too, however, based on the reference documentation this endpoint is no longer exposed via "web" by default. Thus you need to consider the following steps to access the endpoint
Add the below dependency to your pom.xml
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
Add these two propertiers to your application.properties file:
management.endpoints.web.exposure.include=beans
management.endpoint.beans.enabled=true
Access to your application context beans using /actuator/beans http endpoint
I did one small experiment for this requirement and found this solution. I have created SpringBoot while selecting the modules like WEB, Actuator, HAL and Devtools. I have configured the below property in application properties to load all the endpoints present in actuator.
management.endpoints.web.exposure.include=*
You can see actuator information in, http://localhost:8080/actuator. This will show all the application information along with actuator, status, info,etc.. In that, you can find the http://localhost:8080/actuator/beans which will load all the beans internally created by springboot application.
Once you are able to see all the beans information, I think it's not necessary to print again in main class.
Since, I have already configured rest-hal-browser dependency in my application, when I load the URL of http://localhost:8080, will load the UI to search for different endpoints. In the below image I am searching for actuator information.
Simple way to get all beans
ApplicationContext ctx =SpringApplication.run(DemoApplication.class, args);
String [] beans = ctx.getBeanDefinitionNames();
Arrays.sort(beans);
System.out.println("#############");
for(String s:beans) {
System.out.println(s + " of type " + ctx.getBean(s).getClass());
}