Cant access property of managed bean from another managed bean - jsf

Question

I want to access the property of a #SessionScoped bean in another bean using #ManagedProperty. In short, I want to access the name property of firstBean in secondBean.
#ManagedBean
#SessionScoped
public class FirstBean implements Serializable{
private String name;
//...other attributes
//...constructor
public String getSelectedModel() {
return selectedModel;
}
public void setSelectedModel(String selectedModel) {
this.selectedModel = selectedModel;
}
//other getters&setters
}
And second bean:
#ManagedBean
#SessionScoped
public class SecondBean implements Serializable{
#ManagedProperty(value="#{firstBean}")
private FirstBean firstBean
public SecondBean() {
System.out.println(firstBean.getName());
}
public IndexBean getFirstBean() {
return firstBean;
}
public void setFirstBean(FirstBean firstBean) {
this.firstBean = firstBean;
}
When I run this, I always get NullPointerException on System.out.println(firstBean.getName()); in the constructor of second bean, which seems to mean that I need to create a new instance of firstBean.
But strangely, when I commented out this line, I can do something like this with no errors, which means that firstBean is actually a property of secondBean.
<h:outputText value="#{secondBean.firstBean.name}" />
What's the problem here?

Answer 1

It's not possible to access an injected dependency in the constructor. You're basically expecting that Java is able to do something like this:
SecondBean secondBean; // Declare.
secondBean.firstBean = new FirstBean(); // Inject.
secondBean = new SecondBean(); // Construct.
It's absolutely not possible to set an instance variable if the instance is not constructed yet. Instead, it works as follows:
SecondBean secondBean; // Declare.
secondBean = new SecondBean(); // Construct.
secondBean.firstBean = new FirstBean(); // Inject.
Then, in order to perform business actions based on injected dependencies, use a method annotated with #PostConstruct. It will be invoked by the dependency injection manager directly after construction and dependency injection.
So, just replace
public SecondBean() {
System.out.println(firstBean.getName());
}
by
#PostConstruct
public void init() { // Note: method name is fully to your choice.
System.out.println(firstBean.getName());
}