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

Question

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()?

Answer 1

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

Answer 2

A simple way to do this is using ApplicationContext.getBean().

It's worth pointing out that this is considered bad practice, since it breaks inversion of control.