These annotations are class-level annotations, which get registered with the Spring container. The following figure shows stereotype annotations:

Let's use @Component in the application. We will use Ch02_Reference_DI as a base project, and perform the following steps:

1. Create Ch02_Demo_Annotation, add all the jars that we added earlier, and along with them, add spring-aop.jar to it as well.
2. Create or copy Address.java in the com.ch02.beans package.
3. Create or copy Customer.java in the com.ch02.stereotype.annotation package. Rename it as Customer_Component.java.
4. Add to it the default constructor, as the code to which we refer does not have any default constructor. The code can be as follows:

public Customer_Component() { 
  // TODO Auto-generated constructor stub 
  cust_id=100; 
  cust_name="cust_name"; 
  cust_address=new Address(); 
  cust_address.setBuild_no(2); 
  cust_address.setCity_name("Delhi"); 
} 

5. Annotate the class with @Component, as shown in the following piece of code:

@Component 
public class Customer_Component {   } 

Here, we configured a component that is auto-scannable. By default, the id of this component will be a decapitalized class name. In our case, it's customer_Component. If we want to use customized id , we can modify the configuration. In case we want to use myObject as the bean id, we need to update the code as follows:

@Component(value="myObject") 

Moreover, there is no need to configure it in XML as we did earlier. However, we will still need XML for some other configurations.

6. Create or copy customer.xml in classpath.
7. Add the following code to consider the annotations:

<context:annotation-config/> 

We have already seen how to configure the context namespace.

8. Create TestCustomer_component, and get the bean of Customer_Component, as shown in the following piece of code, in order to find out what is the output of our configuration:

public class TestCustomer_component { 
  public static void main(String[] args) { 
    // TODO Auto-generated method stub 
    ApplicationContext context = new 
    ClassPathXmlApplicationContext("customer.xml"); 
    Customer_Component customer = (Customer_Component)  
      context.getBean("customer_Component"); 
    System.out.println(customer.getCust_name() + "	" +  
      customer.getCust_id() +  
    customer.getCust_address()); 
  } 
} 

On execution, we will get the following stack trace of exception:

9. If we did everything right, then why do we still get an exception? The reason is that although we made the components auto-scannable, we forgot to tell the container where to scan for annotations. Let's configure where to scan for components, as shown in the following lines of code:

<context:component-scan  
base-package="com.ch02.stereotype.*"> 
</context:component-scan> 

Here, all the subpackages of com.ch02.streotype will be scanned to find out the bean which has id as customer_Component.

10. After adding the configuration, we will get the following output, which displays the data member values:

In the same way, we can use the other annotations, but we will discuss them one by one in the upcoming chapters.