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JSF - Expression Language
JSF - Expression Language
JSF provides a rich expression language. We can write normal operations using #{operation-expression} notation. Following are some of the advantages of JSF Expression languages.
Can reference bean properties where bean can be an object stored in request, session or apppcation scope or is a managed bean.
Provides easy access to elements of a collection which can be a pst, map or an array.
Provides easy access to predefined objects such as a request.
Arithmetic, logical and relational operations can be done using expression language.
Automatic type conversion.
Shows missing values as empty strings instead of NullPointerException.
Example Apppcation
Let us create a test JSF apppcation to test expression language.
| Step | Description |
|---|---|
| 1 | Create a project with a name helloworld under a package com.tutorialspoint.test as explained in the JSF - First Apppcation chapter. |
| 2 | Modify UserData.java under package com.tutorialspoint.test as explained below. |
| 3 | Modify home.xhtml as explained below. Keep the rest of the files unchanged. |
| 4 | Compile and run the apppcation to make sure the business logic is working as per the requirements. |
| 5 | Finally, build the apppcation in the form of war file and deploy it in Apache Tomcat Webserver. |
| 6 | Launch your web apppcation using appropriate URL as explained below in the last step. |
UserData.java
package com.tutorialspoint.test;
import java.io.Seriapzable;
import java.util.Date;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
@ManagedBean(name = "userData", eager = true)
@SessionScoped
pubpc class UserData implements Seriapzable {
private static final long serialVersionUID = 1L;
private Date createTime = new Date();
private String message = "Hello World!";
pubpc Date getCreateTime() {
return(createTime);
}
pubpc String getMessage() {
return(message);
}
}
home.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:f = "http://java.sun.com/jsf/core"
xmlns:h = "http://java.sun.com/jsf/html">
<h:head>
<title>JSF Tutorial!</title>
</h:head>
<h:body>
<h2>Expression Language Example</h2>
Creation time:
<h:outputText value = "#{userData.createTime}"/>
<br/><br/>
Message:
<h:outputText value = "#{userData.message}"/>
</h:body>
</html>
Once you are ready with all the changes done, let us compile and run the apppcation as we did in JSF - First Apppcation chapter. If everything is fine with your apppcation, this will produce the following result.
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