The h:commandButton component is an important one among those components that are provided by JSF. This component does render an HTML submit button that work as a simple <input type=”submit”/>. JSF 2 does enhance the h:commandButton by allowing the command to invoke an associated action by passing a parameters for it. The main attribute of the h:commandButton is an action attribute that accepts a method-binding expression for a backing bean action (method) to be invoked when the user has clicked on the button. The method-binding expression has the following roles to be accepted as a proper action.
- The defined method (action) in the backing bean should have a public access modifier.
- The defined method (action) in the backing bean should have a String as returned type. (This string token will be consumed by the JavaServer Faces Navigation Handler).
- Starting with JSF 2.0, the defined method can accept a parameter values in the method signature, this feature is useful for providing parameters to the actions of buttons and links. When a method reference is evaluated, the parameters are evaluated and passed to the method.
The h:commandButton and h:commandLink are the primary components for navigating within a JSF application, when a button or link is clicked (activated), a POST request sends the form data back to the server and the JSF framework lifecycle has started. The main difference between h:commandButton and h:commandLink that the latter provides a predefined code at the onclick JavaScript attribute
Also Read:
1. Managed Bean
LoginBean.java
[code lang=”java”]
package net.javabeat.jsf;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
@ManagedBean
@SessionScoped
public class LoginBean {
private String username = "";
private String password = "";
private String authority = "";
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getAuthority() {
return authority;
}
public void setAuthority(String authority) {
this.authority = authority;
}
public String login(String type){
this.authority = type;
if(this.username.isEmpty() == false && this.username.equalsIgnoreCase("Josha")
&& this.password.isEmpty() == false && this.password.equals("Josha1@#$")){
return "success";
}
return "failure";
}
}
[/code]
2. The Views
login.xhtml
[code lang=”xml”]
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core">
<h:form>
<h1>
<h:outputText value="JavaBeat JSF 2.2 Examples" />
</h1>
<h2>
<h:outputText value="CommandButton Example" />
</h2>
<table>
<tr><td>Enter Your Username : </td><td><h:inputText id="username" value="#{loginBean.username}"/></td></tr>
<tr><td>Enter Your Password : </td><td><h:inputSecret value="#{loginBean.password}"/></td></tr>
<tr><td colspan="2"><h:commandButton value="Login" action="#{loginBean.login(‘Admin’)}"/></td></tr>
</table>
<br/>
</h:form>
</html>
[/code]
success.xhtml
[code lang=”xml”]
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core">
<h:form>
<h1>
<h:outputText value="JavaBeat JSF 2.2 Examples" />
</h1>
<h2>
<h:outputText value="CommandButton Example" />
</h2>
Welcome <h:outputText value="#{loginBean.username}"/>
<br/>
You’re Logged in By <h:outputText value="#{loginBean.authority}"/> Authority
<br/>
</h:form>
</html>
[/code]
failure.xhtml
[code lang=”xml”]<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core">
<h:form>
<h1>
<h:outputText value="JavaBeat JSF 2.2 Examples" />
</h1>
<h2>
<h:outputText value="CommandButton Example" />
</h2>
Login Failure, Please Try Again !
<br/>
</h:form>
</html>[/code]
3. The Deployment Descriptor (web.xml)
web.xml
[code lang=”xml”]
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
id="WebApp_ID" version="2.5" metadata-complete="true">
<context-param>
<description>State saving method: ‘client’ or ‘server’ (=default). See JSF Specification 2.5.2</description>
<param-name>javax.faces.STATE_SAVING_METHOD</param-name>
<param-value>client</param-value>
</context-param>
<context-param>
<param-name>javax.faces.application.CONFIG_FILES</param-name>
<param-value>/WEB-INF/faces-config.xml</param-value>
</context-param>
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>/faces/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.xhtml</url-pattern>
</servlet-mapping>
<listener>
<listener-class>com.sun.faces.config.ConfigureListener</listener-class>
</listener>
</web-app>
[/code]
4. JSF 2 CommandButton Demo
The below snapshots demonstrates the using of h:commandButton with JSF 2, in that the action represented by the h:commandButton will be used for sending a parameter determines the type of authority that the user has logged with. The h:commandButton does associate with the a navigation handler, so a navigation to a proper view will be happened in case the login process has succeeded or failed.
[wpdm_file id=13]
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