How to do it...

Let us illustrate the eager and lazy loading of beans in a context definition using these steps:

1. In the case of the XML-based ApplicationContext, eager loading means all the beans in the definition will be loaded and initialized aggressively in the heap memory during start-up (for example, pre-instantiating). To opt for this type of initialization, each <bean> has an attribute lazy-init, which must be set to false. Open ch02-beans.xml in the project ch02-xml and add the following bean:

<bean id="empRec6" class="org.packt.starter.ioc.model.Employee" 
  lazy-init="false"> 
  <constructor-arg><value>Diego</value></constructor-arg> 
  <constructor-arg><value>Silang</value></constructor-arg> 
  <constructor-arg> 
    <value>December 16, 1965</value>
  </constructor-arg> 
  <constructor-arg><value>55</value></constructor-arg> 
  <constructor-arg><value>87000</value></constructor-arg> 
  <constructor-arg><value>Guitarist</value></constructor-arg> 
  <constructor-arg><ref bean="dept4"></ref></constructor-arg> 
</bean> 

1. In the case of the JavaConfig approach, by default @Bean loads aggressively and we do not have a special annotation or metadata for eager initialization.
2. The other option of bean loading happens only during the fetching stage (for example, the use of the getBean() method) and this is called lazy loading. In the XML-based container, we set the lazy-init attribute of a <bean> to true to implement lazy bean loading. Using the same class models in Step 1, apply the necessary changes as follows:

<bean id="empRec6" class="org.packt.starter.ioc.model.Employee" 
  lazy-init="true"> 
   // refer to sources 
</bean> 

1. For JavaConfig, Spring has a method-level annotation @Lazy, which can be applied to @Bean objects to perform lazy loading:

@Lazy 
@Bean 
public Employee empRec4(Department dept2){ 
   Employee empRec4 = new Employee("Diego","Silang", 
new Date(65,11, 15), 55, 85000.00, "guitarist", dept4()); 
   return empRec4; 
}