getting new bean instances of referencing beans every time - spring

Question

I have two queries ...
1) I have a query that beans are intialized in the spring container itself when the spring container is intialiazed and before the call is made to the get bean() method , this is the default behavior , how can I configure the application in such way that bean should be initalized in container only when a call is made of getbean() is made, shall we declare the bean as prototype to achieve this.
2) second query is that first please go through the below example first...
<beans>
<bean id="triangle" class="Demo.Triangle" scope="singleton" >
<property name="pointA" ref="zeropoint"/>
<property name="pointB" ref="firstpoint"/>
<property name="pointC" ref="secondpoint"/>
</bean>
<bean id="zeropoint" class="Demo.Point" scope="prototype" >
<property name="x" value="10" />
<property name="y" value="20" />
</bean>
<bean id="firstpoint" class="Demo.Point" scope="prototype" >
<property name="x" value="10" />
<property name="y" value="20" />
</bean>
<bean id="secondpoint" class="Demo.Point" scope="prototype">
<property name="x" value="10" />
<property name="y" value="20" />
</bean>
As indicated above that triangle bean is singleton and it references bean are protoype now when I access singleton the other refernces beans zeropoint,firstpoint and secondpoint are also initaizes only once with respect to triangle but Here I want that every time new instance of these three beans to be get created when the triangle bean is fetched , Please advise how that is achieable. is it achievable through my pojo implementing ApplicationContextAware interface, Please advise

Answer 1

Instead of relying on Spring infrastructure (BeanFactoryAware) I recommend trying lookup method feature:
abstract class Triangle {
public abstract Point createZeroPoint();
public abstract Point createFirstPoint();
public abstract Point createSecondPoint();
public void foo() {
Point p0 = createZeroPoint();
Point p1 = createFirstPoint();
Point p2 = createSecondPoint();
}
}
Every time you call create*Point() abstract method, it creates new instance of Point. But how do you implement this method and how does it know which bean to return? Spring implements this for you!
<bean id="triangle" class="Demo.Triangle" scope="singleton">
<lookup-method name="createZeroPoint" bean="zeropoint"/>
<lookup-method name="createFirstPoint" bean="firstpoint"/>
<lookup-method name="createSecondPoint" bean="secondpoint"/>
</bean>
Check out the comprehensive documentation: 4.4.6.1 Lookup method injection.

Answer 2

Its called Lazy loading
<bean id="myBean" class="a.b.MyBean" lazy-init="true"/>
First note that your firstpoint and secondpoint beans don't have a valid scope definition (you missed the scope=)
Prototype scope means that every bean that requires a prototype bean gets its own instance. If would define multiple triangles which all have a dependency to zeropoint every triangle would a separate zeropoint instance.
If you need new point instances inside your triangle class (e.g. every time you call a method of triangle) the best way is to receive instances directly from the bean factory:
E.g.
class MyClass implements BeanFactoryAware {
private BeanFactory beanFactory;
public void setBeanFactory(BeanFactory beanFactory) {
this.beanFactory = beanFactory;
}
public void doSomethingThatRequiresNewInstance() {
Triangle t = beanFactory.getBean("zeropoint", Triangle.class);
// because zeropoint is defined as prototype you get a new instance everytime you call getBean(..)
}
}