AIR.Common.Web.taglib.JsfHelpers.java Source code

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Here is the source code for AIR.Common.Web.taglib.JsfHelpers.java

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/*******************************************************************************
 * Educational Online Test Delivery System 
 * Copyright (c) 2014 American Institutes for Research
 *   
 * Distributed under the AIR Open Source License, Version 1.0 
 * See accompanying file AIR-License-1_0.txt or at
 * http://www.smarterapp.org/documents/American_Institutes_for_Research_Open_Source_Software_License.pdf
 ******************************************************************************/
/**
 * 
 */
package AIR.Common.Web.taglib;

import java.io.IOException;
import java.util.Map;
import java.util.UUID;

import javax.el.ELContext;
import javax.el.ExpressionFactory;
import javax.el.ValueExpression;
import javax.faces.FacesException;
import javax.faces.application.Application;
import javax.faces.application.Resource;
import javax.faces.component.UIComponent;
import javax.faces.component.UIPanel;
import javax.faces.component.html.HtmlPanelGroup;
import javax.faces.context.FacesContext;
import javax.faces.view.facelets.FaceletContext;

import org.apache.commons.lang3.StringUtils;

/**
 * @author Shiva BEHERA [sbehera@air.org]
 * 
 */
/*
 * we arrived at this solution from multiple different pathways. we looked into
 * FacesServlet and how it renders page. also there were multiple queries
 * floating around on the internet regarding this problem. this particular
 * snippet has been extracted from the following link:
 * http://stackoverflow.com/questions
 * /17411762/insert-composite-component-programatically-in-jsf-via-custom-tag
 * 
 * the significant different between our solution and this one was that we were
 * not doing parent.pushComponentToEL and parent.popComponentFromEL.
 */
// TODO Shiva: it is still not clear what are the implications of
// popComponentFromELs and pushComponentToEL

// TODO Shiva: document what is going on here and how to use this. The use of
// K,V in includeCompositeComponent is very confusing.
public class JsfHelpers {
    private static final String JAVAX_FACES_GROUP = "javax.faces.Group";

    public static void setValueExpressions(UIComponent component, Map<String, String> valueExpressions,
            FacesContext context) {
        if (valueExpressions == null || valueExpressions.size() == 0)
            return;
        if (context == null) {
            context = FacesContext.getCurrentInstance();
        }

        Application application = context.getApplication();
        // http://stackoverflow.com/a/16058002/1961102
        if (valueExpressions != null && !valueExpressions.isEmpty()) {
            ExpressionFactory factory = application.getExpressionFactory();
            ELContext ctx = context.getELContext();
            for (Map.Entry<String, String> entry : valueExpressions.entrySet()) {
                ValueExpression expr = factory.createValueExpression(ctx, entry.getValue(), Object.class);
                component.setValueExpression(entry.getKey(), expr);
            }
        }
    }

    /**
     * Source:
     * http://stackoverflow.com/questions/15828540/programmatically-create-
     * and-add-composite-component-in-backing-bean
     * 
     * @param parent
     * @param libraryName
     * @param resourceName
     * @param id
     */
    @SuppressWarnings("unchecked")
    public static <K, V> V includeCompositeComponent(UIComponent parent, String libraryName, String resourceName,
            String id, Map<String, String> valueExpressions, IUpdater<K> updater)
            throws IncompatibleTypeException, JsfComponentIncludeException {
        // Prepare.
        FacesContext context = FacesContext.getCurrentInstance();
        Application application = context.getApplication();
        FaceletContext faceletContext = (FaceletContext) context.getAttributes()
                .get(FaceletContext.FACELET_CONTEXT_KEY);

        // This basically creates <ui:component> based on <composite:interface>.
        Resource resource;
        if (application.getResourceHandler().libraryExists(libraryName)) {
            resource = application.getResourceHandler().createResource(resourceName, libraryName);
        } else {
            resource = application.getResourceHandler().createResource(resourceName);
        }
        UIComponent composite = application.createComponent(context, resource);
        if (StringUtils.isEmpty(id)) {
            // generate a unique id. remember ids cannot begin with a number - the
            // first character has to be a letter.
            id = "id_" + UUID.randomUUID().toString();
        }
        composite.setId(id); // Mandatory for the case composite is part of UIForm!
                             // Otherwise JSF can't find inputs.
                             // copy values.
        if (updater != null) {
            try {
                updater.update((K) composite);
            } catch (ClassCastException exp) {
                throw new IncompatibleTypeException(exp);
            }
        }

        setValueExpressions(composite, valueExpressions, context);

        // This basically creates <composite:implementation>.
        // Shiva: Below was what was in the original source. I have replaced it with
        // what we are comfortable with.
        /*
         * UIComponent implementation = application.createComponent (context,
         * UIPanel.COMPONENT_TYPE, JAVAX_FACES_GROUP);
         */
        UIComponent implementation = application.createComponent(HtmlPanelGroup.COMPONENT_TYPE);
        implementation.setRendererType("javax.faces.Group");

        composite.getFacets().put(UIPanel.COMPOSITE_FACET_NAME, implementation);

        // Now include the composite component file in the given parent.
        parent.getChildren().add(composite);
        parent.pushComponentToEL(context, composite); // This makes #{cc}
                                                      // available.
        try {
            faceletContext.includeFacelet(implementation, resource.getURL());
        } catch (IOException exp) {
            throw new JsfComponentIncludeException(exp);
        }
        parent.popComponentFromEL(context);

        try {
            return (V) composite;
        } catch (ClassCastException exp) {
            throw new IncompatibleTypeException(exp);
        }
    }
}