How to get bean using application context in spring boot

Question

I am developing a SpringBoot project and I want to get the bean by its name using applicationContext  I have tried many solution from web but could not succeed  My Requirement is that I have a controller   ControllerA   and inside the controller I have a method getBean String className   I want to get instance of registered bean  I have hibernate entities and I want to get an instance of the bean by passing the name of class only in getBean method   Please help if someone know the solution

User · Answer

actually you want to get the object from the Spring engine, where the engine already maintaining the object of your required class at that starting of the spring application(Initialization of the Spring engine).Now the thing is you just have to get that object to a reference.

in a service class

@Autowired
private ApplicationContext context;

SomeClass sc = (SomeClass)context.getBean(SomeClass.class);

now in the reference of the sc you are having the object. Hope explained well. If any doubt please let me know.

User · Answer

You can Autowire the ApplicationContext  either as a field   Autowired private ApplicationContext context    or a method   Autowired public void context ApplicationContext context    this context   context      Finally use  context getBean SomeClass class

User · Answer

One API method I use when I m not sure what the bean name is org springframework beans factory ListableBeanFactory getBeanNamesForType java lang Class lt   gt    I simple pass it the class type and it retrieves a list of beans for me  You can be as specific or general as you d like to retrieve all the beans relate with that type and its subtypes  example  Autowired ApplicationContext ctx       SomeController controller   ctx getBeanNamesForType SomeController

User · Answer

Just use      org springframework beans factory BeanFactory getBean java lang Class    Example    Component public class Example         Autowired     private ApplicationContext context       public MyService getMyServiceBean             return context getBean MyService class                 your code uses getMyServiceBean

User · Answer

Using SpringApplication run Class lt   gt  primarySource  String    arg  worked for me  E g    SpringBootApplication public class YourApplication        public static void main String   args            ConfigurableApplicationContext context   SpringApplication run YourApplication class  args

User · Answer

If you are inside of Spring bean  in this case  Controller bean  you shouldn t use Spring context instance at all  Just autowire className bean directly   BTW  avoid using field injection as it s considered as bad practice

User · Answer

You can use ServiceLocatorFactoryBean  First you need to create an interface for your class  public interface YourClassFactory       YourClass getClassByName String name       Then you have to create a config file for ServiceLocatorBean   Configuration  Component public class ServiceLocatorFactoryBeanConfig         Bean     public ServiceLocatorFactoryBean serviceLocatorBean            ServiceLocatorFactoryBean bean   new ServiceLocatorFactoryBean            bean setServiceLocatorInterface YourClassFactory class           return bean            Now you can find your class by name like that   Autowired private YourClassfactory factory   YourClass getYourClass String name       return factory getClassByName name

User · Answer

You can use the ApplicationContextAware class that can provide the application context   public class ApplicationContextProvider implements ApplicationContextAware        private static ApplicationContext ctx   null       public static ApplicationContext getApplicationContext             return ctx              Override     public void setApplicationContext final ApplicationContext ctx  throws BeansException           ApplicationContextProvider ctx   ctx                        Tries to autowire the specified instance of the class if one of the specified        beans which need to be autowired are null                 param classToAutowire        the instance of the class which holds  Autowire                                      annotations         param beansToAutowireInClass the beans which have the  Autowire annotation                                      in the specified   classToAutowire              public static void autowire Object classToAutowire  Object    beansToAutowireInClass            for  Object bean   beansToAutowireInClass                if  bean    null                    ctx getAutowireCapableBeanFactory   autowireBean classToAutowire

User · Answer

You can use ApplicationContextAware   ApplicationContextAware  Interface to be implemented by any object that wishes to be notified of the ApplicationContext that it runs in  Implementing this interface makes sense for example when an object requires access to a set of collaborating beans   There are a few methods for obtaining a reference to the application context  You can implement ApplicationContextAware as in the following example  package hello   import org springframework beans BeansException  import org springframework context ApplicationContext  import org springframework context ApplicationContextAware     Component public class ApplicationContextProvider implements ApplicationContextAware        private ApplicationContext applicationContext        Override     public void setApplicationContext ApplicationContext applicationContext  throws BeansException           this applicationContext   applicationContext           public ApplicationContext getContext             return applicationContext                Update  When Spring instantiates beans  it looks for ApplicationContextAware implementations  If they are found  the setApplicationContext   methods will be invoked  In this way  Spring is setting current applicationcontext  Code snippet from Spring s source code  private void invokeAwareInterfaces Object bean                                 if  bean instanceof ApplicationContextAware                        ApplicationContextAware bean  setApplicationContext this applicationContext           Once you get the reference to Application context  you get fetch the bean whichever you want by using getBean

User · Answer

Even after adding  Autowire if your class is not a RestController or Configuration Class  the applicationContext object was coming as null  Tried Creating new class with below and it is working fine   Component public class SpringContext implements ApplicationContextAware      private static ApplicationContext applicationContext       Override     public void setApplicationContext ApplicationContext applicationContext  throws       BeansException       this applicationContext applicationContext           you can then implement a getter method in the same class as per your need to get the bean  Like      applicationContext getBean String serviceName Interface Class

[java] How to get bean using application context in spring boot

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