Internationalised labels in JSF/Facelets

StackOverflow https://stackoverflow.com/questions/86202

Question

Does Facelets have any features for neater or more readable internationalised user interface text labels that what you can otherwise do using JSF?

For example, with plain JSF, using h:outputFormat is a very verbose way to interpolate variables in messages.

Clarification: I know that I can add a message file entry that looks like:

label.widget.count = You have a total of {0} widgets.

and display this (if I'm using Seam) with:

<h:outputFormat value="#{messages['label.widget.count']}">
   <f:param value="#{widgetCount}"/>
</h:outputFormat>

but that's a lot of clutter to output one sentence - just the sort of thing that gives JSF a bad name.

Was it helpful?

Solution

You could create your own faces tag library to make it less verbose, something like:

<ph:i18n key="label.widget.count" p0="#{widgetCount}"/>

Then create the taglib in your view dir: /components/ph.taglib.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE facelet-taglib PUBLIC "-//Sun Microsystems, Inc.//DTD Facelet Taglib 1.0//EN" "https://facelets.dev.java.net/source/browse/*checkout*/facelets/src/etc/facelet-taglib_1_0.dtd">

<facelet-taglib xmlns="http://java.sun.com/JSF/Facelet">
    <namespace>http://peterhilton.com/core</namespace>

    <tag>
        <tag-name>i18n</tag-name>
        <source>i18n.xhtml</source>
    </tag>

</facelet-taglib>

create /components/i18n.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">
<ui:composition 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:outputFormat value="#{messages[key]}">
            <!-- crude but it works -->
        <f:param value="#{p0}" />
        <f:param value="#{p1}" />
        <f:param value="#{p2}" />
        <f:param value="#{p3}" />
    </h:outputFormat>

</ui:composition>

You can probably find an elegant way of passing the arguments with a little research.

Now register your new taglib in web.xml

<context-param>
<param-name>facelets.LIBRARIES</param-name>
<param-value>
        /components/ph.taglib.xml
    </param-value>
</context-param>

Just add xmlns:ph="http://peterhilton.com/core" to your views and you're all set!

OTHER TIPS

Since you're using Seam, you can use EL in the messages file.

Property:

label.widget.count = You have a total of #{widgetCount} widgets.

XHTML:

<h:outputFormat value="#{messages['label.widget.count']}" />

This still uses outputFormat, but is less verbose.

I've never come across another way of doing it other than outputFormat. It is unfortunately quite verbose.

The only other thing I can suggest is creating the message in a backing bean and then outputting that rather than messageFormat.

In my case I have Spring's MessageSource integrated with JSF (using MessageSourcePropertyResolver). Then, it's fairly easy in your backing beans to get parameterised messages - you just need to know which Locale your user is in (again, I've got the Locale bound to a backing bean property so it's accessible via JSF or Java).

I think parameters - particular in messages - are one thing JSF could really do better!

I have been thinking about this more, and it occurs to me that I could probably write my own JSTL function that takes a message key and a variable number of parameters:

<h:outputText value="#{my:message('label.widget.count', widgetCount)}"/>

and if my message function HTML-encodes the result before output, I wouldn't even need to use the h:outputText

#{my:message('label.widget.count', widgetCount)}

You can use the Seam Interpolator:

<h:outputText value="#{interpolator.interpolate(messages['label.widget.count'], widgetCount)}"/>

It has @BypassInterceptors on it so the performance should be ok.

You can use the Bean directly if you interpolate the messages.

label.widget.count = You have a total of #{widgetCount} widgets.
label.welcome.message = Welcome to #{request.contextPath}!
label.welcome.url = Your path is ${pageContext.servletContext}.

${messages['label.widget.count']} is enougth.

This one works great using Spring:

package foo;

import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ExpressionFactory;
import javax.el.ResourceBundleELResolver;
import javax.faces.context.FacesContext;

import org.springframework.web.jsf.el.SpringBeanFacesELResolver;

public class ELResolver extends SpringBeanFacesELResolver {
    private static final ExpressionFactory FACTORY = FacesContext
            .getCurrentInstance().getApplication().getExpressionFactory();
    private static final ResourceBundleELResolver RESOLVER = new ResourceBundleELResolver();

    @Override
    public Object getValue(ELContext elContext, Object base, Object property)
            throws ELException {
        Object result = super.getValue(elContext, base, property);
        if (result == null) {
            result = RESOLVER.getValue(elContext, base, property);
            if (result instanceof String) {
                String el = (String) result;
                if (el.contains("${") | el.contains("#{")) {
                    result = FACTORY.createValueExpression(elContext, el,
                            String.class).getValue(elContext);
                }
            }
        }
        return result;
    }
}

And...

You need to change the EL-Resolver in faces-config.xml from org.springframework.web.jsf.el.SpringBeanFacesELResolver to

Regards

<el-resolver>foo.ELResolver</el-resolver>

Use ResourceBundle and property files.

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