Access a managed bean from event listener – JSF
Published: November 9, 2010 , Updated: November 9, 2010 , Author: mkyong
Problem
How can a JSF event listener class access another managed bean? See scenario below :
JSF page…
<h:selectOneMenu value="#{country.localeCode}" onchange="submit()"> <f:valueChangeListener type="com.mkyong.CountryValueListener" /> <f:selectItems value="#{country.countryInMap}" /> </h:selectOneMenu>
country managed bean…
package com.mkyong; import java.io.Serializable; import javax.faces.bean.ManagedBean; import javax.faces.bean.SessionScoped; @ManagedBean(name="country") @SessionScoped public class CountryBean implements Serializable{ private String localeCode; public void setLocaleCode(String localeCode) { this.localeCode = localeCode; } //... }
ValueChangeListener…
package com.mkyong; import javax.faces.event.AbortProcessingException; import javax.faces.event.ValueChangeEvent; import javax.faces.event.ValueChangeListener; public class CountryValueListener implements ValueChangeListener{ @Override public void processValueChange(ValueChangeEvent event) throws AbortProcessingException { //how to access the existing country managed bean? //country.setLocaleCode(event.getNewValue().toString()); } }
Solution
Actually, there are many ways to access an existing managed bean from an event listener class or another managed bean. See examples :
1. getApplicationMap()
If country managed bean is declared in application scope.
CountryBean country = (CountryBean) FacesContext.getCurrentInstance(). getExternalContext().getApplicationMap().get("country");
2. getRequestMap()
If country managed bean is declared in request scope.
CountryBean country = (CountryBean) FacesContext.getCurrentInstance(). getExternalContext().getRequestMap().get("country");
3. getSessionMap()
If country managed bean is declared in session scope.
CountryBean country = (CountryBean) FacesContext.getCurrentInstance(). getExternalContext().getSessionMap().get("country");
4. ELResolver()
Using ELResolver.
FacesContext context = FacesContext.getCurrentInstance(); CountryBean country = (CountryBean) context. getELContext().getELResolver().getValue(context.getELContext(), null,"country");
5. ValueExpression()
Using ValueExpression.
FacesContext context = FacesContext.getCurrentInstance(); CountryBean country = (CountryBean) context.getApplication().getExpressionFactory() .createValueExpression(context.getELContext(), "#{country}", CountryBean.class) .getValue(context.getELContext());
6. evaluateExpressionGet()
Using evaluateExpressionGet.
FacesContext context = FacesContext.getCurrentInstance(); CountryBean country = (CountryBean)context.getApplication() .evaluateExpressionGet(context, "#{country}", CountryBean.class);
Reference
- getApplicationMap() java Doc
- getRequestMap() JavaDoc
- getSessionMap() JavaDoc
- getELResolver() JavaDoc
- createValueExpression() JavaDoc
- evaluateExpressionGet() JavaDoc
Great article on JSF managed beans, thanks. I have a question, though: I need to access an application-scoped managed bean to modify certain properties from within an HttpSessionListener.
I already used something like the following:
externalContext = FacesContext.getCurrentInstance().getExternalContext() causes a null pointer exception already, and even if it didn’t I’m not sure appBean could be accessible the above way.
Any ideas?