Can I use multiple managed bean in the same xhtml page?
Yes, you can, I highly recommend you to try it :).
What is its impact?
This depends on the managed beans scopes. A good example is having a view to register a new address and shows the logged user info at the top of the page, similar to Amazon site where you add a new shipping address.
In this case, you can have among three managed beans:
- A
@SessionScoped bean that will show the logged user info. In case of amazon view, it shows only the first name.
- A
@ApplicationScoped bean that will provide the data for Countries. This info doesn't change too often (at least that a new country is born every day =\).
- A
@ViewScoped bean that will handle the request data, error messages and the registration.
A sample of the above explanation in Facelets code:
<div id="top">
Hello #{sessionBean.user.firstName}
</div>
<div id="body">
<h1>Add an address</h1>
<h:form id="frmAddress">
<h:panelGrid columns="2">
<h:outputText value="Address" />
<h:inputText id="txtAddress" value="#{viewBean.address}" />
<h:outputText value="Country" />
<h:selectOneMenu id="ddlCountry" value="#{viewBean.selectedCountry}">
<f:selectItems value="#{applicationBean.countries}" var="country"
itemLabel="#{country.name}" itemValue="#{country}" />
</h:selectOneMenu>
</h:panelGrid>
<h:messages id="msgErrors" />
<h:commandButton value="Save address" action="#{viewBean.saveAddress}" />
</h:form>
</div>
Note: this is nor a good nor a bad practice, just give it a try to see how this behaves. The impact is defined how each managed bean behaves in the page, so it will be pretty neat or a really bad experience, based on how you have defined the beans.
Related info:
- Why JSF calls getters multiple times
- Communication in JSF 2: Managed bean scopes
