@ManagedProperty - Inject one request scoped bean into another request scoped bean

Question

I have this SearchBean:

@ManagedBean(name = "searchBean")
@RequestScoped
public class SearchBean implements Serializable
{
    private String input = null;

    // getter methods
    public String getInput() {
        return input;
    }

    // setter method
    public void setInput(String input) {
        this.input = input;
    }

    public String Submit() {
        return null;
    }    
}

Can I inject it into another bean using @ManagedProperty. For example:

@ManagedBean(name = "bookBean")
@RequestScoped
public class BookBean implements Serializable
{
    @ManagedProperty(value = "#{searchBean}")
    private SearchBean searchBean;  

    @PostConstruct
    public void init()
    {   
       System.out.println("Value: " + searchBean.getInput());
    }

    public SearchBean getSearchBean() {
       return searchBean;
    }

    public void setSearchBean(SearchBean searchBean) {
       this.searchBean = searchBean;
    }   
}

And the Facelet (search.xhtml):

<h:form id="formSearch">
   <h:commandButton value="Search" action="#{searchBean.Submit}" />
</h:form>

UPDATE: I have search.xhtml inserted into book.xhtml via a ui:insert component as follow:

<h:form id="formBooks">
   <ui:insert name="search">
      <ui:include src="/templates/common/search.xhtml"/>
   </ui:insert> 
</h:form>

The searchBean.getInput() method above should return a value as a result of a form's submission. Is the above method of injection possible?

Answer 1

I assume that SearchBean.input will be bound to an input field:

public class SearchBean implements Serializable {
    private String input = null;

Something like this:

<h:inputText value="#{searchBean.input}" />

If so, then this will be null:

@PostConstruct
public void init()
{   
   System.out.println("Value: " + searchBean.getInput());
}

But, assuming a value has been set, it will not be null when this method is invoked:

public String Submit() {
    return null;
}

---

Image from Richard Hightower's JSF for nonbelievers: The JSF application lifecycle.

The reason is due to how the JSF lifecycle works:

1. When #{searchBean...} is first resolved and found not to exist:
   • The bean is instantiated
   • Any dependency injections are performed (there aren't any in this case)
   • @PostConstruct method is invoked
   • The bean is placed into scope
2. Assuming the Apply Request Values and Validations phases succeed, SearchBean.setInput(String) is invoked in the Update Model Values phase
3. SearchBean.Submit() is invoked in the Invoke Application phase

This process is defined in the JSF specification.

---

Now, if SearchBean.input were injected directly from the parameter map, it would not be null during @PostConstruct:

@ManagedProperty(value = "#{param.someParamName}")
private String input;

However, there aren't any real advantages to this - you're skipping any input validation and you can't use SearchBean.input as a field binding because it will be overwritten in the Update Model Values phase.

The SearchBean.Submit() method is where your application logic for performing the search should go.