In JSF, “f:param” tag allow you to pass a parameter to a component, but it’s behavior is different depends on which type of component it’s attached. For example,

1. f:param + h:outputFormat

If attach a “f:param” tag to “h:outputFormat“, the parameter is specifies the placeholder.

<h:outputFormat value="Hello,{0}. You are from {1}.">
	<f:param value="JSF User" />
	<f:param value="China" />
</h:outputFormat>

Here’s the output – “Hello JSF User. You are from China“.

2. f:param + Other Component

If you attach a “f:param” tag to other components like “h:commandButton” , the parameter is turned into request parameter.

<h:commandButton id="submitButton" 
	value="Submit - US" action="#{user.outcome}">
	<f:param name="country" value="China" />
</h:commandButton>

In user bean, you can get back the parameter value like this :

	Map<String,String> params = 
		FacesContext.getExternalContext().getRequestParameterMap();
 
	String countrry = params.get("country");

JSF f:param example

Here’s a JSF 2.0 application, to show the use of f:param tag in both “h:commandButton” and “h:outputFormat” componenets.

1. Managed Bean

A simple managed bean.

UserBean.java

package com.mkyong;
 
import java.util.Map;
 
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import javax.faces.context.FacesContext;
 
@ManagedBean(name="user")
@SessionScoped
public class UserBean{
 
	public String name;
	public String country;
 
	public String outcome(){
 
		FacesContext fc = FacesContext.getCurrentInstance();
		this.country = getCountryParam(fc);
 
		return "result";
	}
 
	//get value from "f:param"
	public String getCountryParam(FacesContext fc){
 
		Map<String,String> params = fc.getExternalContext().getRequestParameterMap();
		return params.get("country");
 
	}
 
	//getter and setter methods
 
}

2. JSF Page

Two JSF pages for demonstration.

default.xhtml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"   
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core"
      >
 
    <h:body>
 
    <h1>JSF 2 param example</h1>
 
      <h:form id="form">
 
	Enter your name :
	<h:inputText size="10" value="#{user.name}" />
 
	<br /><br />
 
	<h:commandButton id="submitButton" 
		value="Submit - US" action="#{user.outcome}">
 
		<f:param name="country" value="United States" />
 
	</h:commandButton>
 
      </h:form>
 
    </h:body>
</html>

result.xhtml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"   
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core"
      >
 
    <h:body>
 
    <h1>JSF 2 param example</h1>
 
     <h3>
     <h:outputFormat value="Hello,{0}. You are from {1}.">
	 <f:param value="#{user.name}" />
	 <f:param value="#{user.country}" />
     </h:outputFormat>
     </h3>
 
    </h:body>
 
</html>

3. Demo

Enter your name, e.g “mkyong”, and click on the button.

jsf2-Param-Example-1

Display the formatted message, “name” from user input, “country” from button parameter.

jsf2-Param-Example-2

Download Source Code

Download It – JSF-2-Param-Example.zip (10KB)

Reference

  1. JSF f:param JavaDoc
Note : You can find more similar articles at - JSF 2 Tutorials
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