retrieve Bean programmatically

问题

@Configuration
public class MyConfig {
    @Bean(name = "myObj")
    public MyObj getMyObj() {
        return new MyObj();
    }
}

I have this MyConfig object with @Configuration Spring annotation. My question is that how I can retrieve the bean programmatically (in a regular class)?

for example, the code snippet looks like this. Thanks in advance.

public class Foo {
    public Foo(){
    // get MyObj bean here
    }
}

public class Var {
    public void varMethod(){
            Foo foo = new Foo();
    }
}

回答1:

Here an Example

public class MyFancyBean implements ApplicationContextAware {

  private ApplicationContext applicationContext;

  void setApplicationContext(ApplicationContext applicationContext) {
    this.applicationContext = applicationContext;
  }

  public void businessMethod() {
    //use applicationContext somehow
  }

}

However you rarely need to access ApplicationContext directly. Typically you start it once and let beans populate themselves automatically.

Here you go:

ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");

Note that you don't have to mention files already included in applicationContext.xml. Now you can simply fetch one bean by name or type:

ctx.getBean("someName")

Note that there are tons of ways to start Spring - using ContextLoaderListener, @Configuration class, etc.

回答2:

Try this:

public class Foo {
    public Foo(ApplicationContext context){
        context.getBean("myObj")
    }
}

public class Var {
    @Autowired
    ApplicationContext context;
    public void varMethod(){
            Foo foo = new Foo(context);
    }
}

回答3:

The simplest (though not the cleanest) approach if you really need to fetch beans from the ApplicationContext is to have your class implement the ApplicationContextAware interface and provide the setApplicationContext() method.

Once you have a reference to the ApplicationContext you have access to many methods that will return bean instances to you.

The downside is that this makes your class aware of the Spring context, which one should avoid unless necessary.

来源：https://stackoverflow.com/questions/25775888/retrieve-bean-programmatically

标签

java

Spring

javabeans