org.metawidget.faces.FacesUtils Maven / Gradle / Ivy
// Metawidget
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package org.metawidget.faces;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.faces.application.Application;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
/**
* Utilities for working with Java Server Faces.
*
* @author Richard Kennard
*/
public final class FacesUtils {
//
// Public statics
//
/**
* Return true if the specified value conforms to the syntax requirements of a
* value binding expression.
*
* This method is a mirror of the one in UIComponentTag.isValueReference, but that
* one is deprecated so may be removed in the future.
*
* @param value
* The value to evaluate
* @throws NullPointerException
* if value is null
*/
public static boolean isExpression( String value ) {
return PATTERN_EXPRESSION.matcher( value ).matches();
}
/**
* @return the original String, not wrapped in #{...}. If the original String was not wrapped,
* returns the original String
*/
public static String unwrapExpression( String value ) {
Matcher matcher = PATTERN_EXPRESSION.matcher( value );
if ( !matcher.matches() ) {
return value;
}
return matcher.group( 3 );
}
/**
* @return the original String, wrapped in #{...}. If the original String was already wrapped,
* returns the original String
*/
public static String wrapExpression( String value ) {
if ( isExpression( value ) ) {
return value;
}
return EXPRESSION_START + unwrapExpression( value ) + EXPRESSION_END;
}
public static void render( FacesContext context, UIComponent component )
throws IOException {
if ( component == null || !component.isRendered() ) {
return;
}
component.encodeBegin( context );
if ( component.getRendersChildren() ) {
component.encodeChildren( context );
} else {
renderChildren( context, component );
}
component.encodeEnd( context );
}
/**
* @return true if the JSF version is 2 or above, false otherwise
*/
public static boolean isJsf2() {
try {
Class.forName( "javax.faces.event.PreRenderViewEvent" );
return true;
} catch ( ClassNotFoundException e ) {
return false;
}
}
public static boolean isPartialStateSavingDisabled() {
FacesContext context = FacesContext.getCurrentInstance();
return ( "false".equals( context.getExternalContext().getInitParameter( "javax.faces.PARTIAL_STATE_SAVING" ) ) );
}
/**
* Create a component using either the JSF 2.x
* createComponent( context, componentType, rendererType ) method, or the JSF 1.x
* createComponent( componentType ) method. The former can be important for JSF 2.x
* controls that need to dynamically include additional resources (such as JavaScript/CSS
* files).
*/
@SuppressWarnings( "unchecked" )
public static T createComponent( String componentType, String rendererType ) {
FacesContext context = FacesContext.getCurrentInstance();
Application application = context.getApplication();
// JSF 2.x
if ( isJsf2() ) {
return (T) application.createComponent( context, componentType, rendererType );
}
// JSF 1.x
return (T) application.createComponent( componentType );
}
//
// Private statics
//
private static void renderChildren( FacesContext context, UIComponent component )
throws IOException {
for ( UIComponent componentChild : component.getChildren() ) {
render( context, componentChild );
}
}
/**
* Match #{...} and ${...}. This mirrors the approach in
* UIComponentTag.isValueReference, but that one is deprecated so may be removed in
* the future.
*
* Like UIComponentTag.isValueReference we allow nested #{...} blocks, because this
* can still be a legitimate value reference:
*
*
* #{!empty bar ? '' : '#{foo}'}
*
*/
private static final Pattern PATTERN_EXPRESSION = Pattern.compile( "((#|\\$)\\{)(.*)(\\})" );
private static final String EXPRESSION_START = "#{";
private static final String EXPRESSION_END = "}";
//
// Private constructor
//
private FacesUtils() {
// Can never be called
}
}