JSF - Expression Language
JSF provides a rich expression language. We can write normal operations using #{operation-expression} notation. Some of the advantages of JSF Expression languages are following.- Can reference bean properties where bean can be a object stored in request, session or application scope or is a managed bean.
- Provides easy access to elements of a collection which can be a list, map or an array.
- Provides easy access to predefined objects such as request.
- Arithmetic, logical, relational operations can be done using expression language.
- Automatic type conversion.
- Shows missing values as empty strings instead of NullPointerException.
Example Application
Let us create a test JSF application 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 Application chapter. |
| 8 | Modify UserData.java under package com.tutorialspoint.test as explained below. |
| 9 | Modify home.xhtml as explained below. Keep rest of the files unchanged. |
| 10 | Compile and run the application to make sure business logic is working as per the requirements. |
| 11 | Finally, build the application in the form of war file and deploy it in Apache Tomcat Webserver. |
| 12 | Launch your web application using appropriate URL as explained below in the last step. |
UserData.java
package com.tutorialspoint.test; import java.io.Serializable; import java.util.Date; import javax.faces.bean.ManagedBean; import javax.faces.bean.SessionScoped; @ManagedBean(name = "userData", eager = true) @SessionScoped public class UserData implements Serializable { private static final long serialVersionUID = 1L; private Date createTime = new Date(); private String message = "Hello World!"; public Date getCreateTime() { return(createTime); } public 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> <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 application as we did in JSF - First Application chapter. If
everything is fine with your application, this will produce following
result:
JSF - Internationalization
Internationalization is a technique in which status messages, GUI component labels, currency, date are not hardcoded in the program instead they are stored outside the source code in resource bundles and retrieved dynamically. JSF provide a very convenient way to handle resource bundle.Following steps are required to internalize a JSF application
Step 1. Define properties files
Create properties file for each locale.Name should be in <file-name>_<locale>.properties format.Default locale can be omitted in file name.
messages.properties
greeting=Hello World!
messages_fr.properties
greeting=Bonjour tout le monde!
Step 2. Update faces-config.xml
faces-config.xml
<application> <locale-config> <default-locale>en</default-locale> <supported-locale>fr</supported-locale> </locale-config> <resource-bundle> <base-name>com.tutorialspoint.messages</base-name> <var>msg</var> </resource-bundle> </application>
Step 3. Use resource-bundle var
home.xhtml
<h:outputText value="#{msg['greeting']}" />
messages.properties
greeting=Hello World!
messages_fr.properties
greeting=Bonjour tout le monde!
faces-config.xml
<?xml version="1.0" encoding="UTF-8"?> <faces-config xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_0.xsd" version="2.0"> <application> <locale-config> <default-locale>en</default-locale> <supported-locale>fr</supported-locale> </locale-config> <resource-bundle> <base-name>com.tutorialspoint.messages</base-name> <var>msg</var> </resource-bundle> </application> </faces-config>
UserData.java
package com.tutorialspoint.test; import java.io.Serializable; import java.util.LinkedHashMap; import java.util.Locale; import java.util.Map; import javax.faces.bean.ManagedBean; import javax.faces.bean.SessionScoped; import javax.faces.context.FacesContext; import javax.faces.event.ValueChangeEvent; @ManagedBean(name = "userData", eager = true) @SessionScoped public class UserData implements Serializable { private static final long serialVersionUID = 1L; private String locale; private static Map<String,Object> countries; static{ countries = new LinkedHashMap<String,Object>(); countries.put("English", Locale.ENGLISH); countries.put("French", Locale.FRENCH); } public Map<String, Object> getCountries() { return countries; } public String getLocale() { return locale; } public void setLocale(String locale) { this.locale = locale; } //value change event listener public void localeChanged(ValueChangeEvent e){ String newLocaleValue = e.getNewValue().toString(); for (Map.Entry<String, Object> entry : countries.entrySet()) { if(entry.getValue().toString().equals(newLocaleValue)){ FacesContext.getCurrentInstance() .getViewRoot().setLocale((Locale)entry.getValue()); } } } }
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:h="http://java.sun.com/jsf/html" xmlns:f="http://java.sun.com/jsf/core" > <h:head> <title>JSF tutorial</title> </h:head> <h:body> <h2>Internalization Language Example</h2> <h:form> <h3><h:outputText value="#{msg['greeting']}" /></h3> <h:panelGrid columns="2"> Language : <h:selectOneMenu value="#{userData.locale}" onchange="submit()" valueChangeListener="#{userData.localeChanged}"> <f:selectItems value="#{userData.countries}" /> </h:selectOneMenu> </h:panelGrid> </h:form> </h:body> </html>Once you are ready with all the changes done, let us compile and run the application as we did in JSF - First Application chapter. If everything is fine with your application, this will produce following result:
Change language from dropdown. You will see the following output.
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