Java – How to access a method a Spring Bean from a class not in the Spring Container

javaspringspring-mvc

I'm not a Spring pro, so please bear with me….

I have three classes:

class SpringBeanA {
    public aMethod() {
        .....
    }
}

class SpringBeanB {

    @Autowired SpringBeanA a;

    public bMethod() {
        a.method();
    }
}

class NONSpringClass {
    .....
    b.method();
    .....
}

b.method() gives a null pointer error, both when accesed via the instances SpringBeanB b = new SpringBeanB() and autowiring SpringBeanB to NONSpringClass.

The autowiring:

class NONSpringClass {

    @Autowired SpringBeanB b;

    .....
    b.method();
    .....
}

How can I successfully call b.method()?

Best Solution

Spring initializes all the objects and keep it in Spring Application Context. You have couple different ways to get access to objects inside Application context

First create a spring configuration class to inject ApplicationContext in to a private attribute and expose as static method.

@Configuration
class StaticApplicationContext implements ApplicationContextAware{

  static ApplicationContext applicationContext = null;

  public void setApplicationContext(ApplicationContext context)    throws BeansException {
    applicationContext = context;
  }
  /**
   * Note that this is a static method which expose ApplicationContext
   **/
  public static ApplicationContext getContext(){
        return applicationContext;
  }

}

Now you can try this in your non spring class,

((SpringBeanB)StaticApplicationContext.getContext.getBean("b")).bMethod();

Please keep in mind, invoking getContext method before spring context initialization may cause NullPointerException. Also accessing beans outside of spring container is not a recommended approach. Ideal way will be to move all beans in to spring container to manage.

If you want to access SpringApplicationContext from a java Servelet please refer WebApplicationContextUtils