org.primefaces.component.importconstants.ImportConstantsTagHandler Maven / Gradle / Ivy

/*
 * Copyright 2009-2014 PrimeTek.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.primefaces.component.importconstants;

import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Collections;
import java.util.Map;

import javax.el.ELContext;
import javax.el.ExpressionFactory;
import javax.el.ValueExpression;
import javax.faces.FacesException;
import javax.faces.application.ProjectStage;
import javax.faces.component.UIComponent;
import javax.faces.context.FacesContext;
import javax.faces.view.facelets.FaceletContext;
import javax.faces.view.facelets.TagAttribute;
import javax.faces.view.facelets.TagConfig;
import javax.faces.view.facelets.TagHandler;
import org.primefaces.context.RequestContext;

/**
 * {@link TagHandler} for the ImportConstants component.
 */
public class ImportConstantsTagHandler extends TagHandler {

	private final TagAttribute typeTagAttribute;
	private final TagAttribute varTagAttribute;

	public ImportConstantsTagHandler(TagConfig config) {
		super(config);

		typeTagAttribute = super.getRequiredAttribute("type");
		varTagAttribute = super.getAttribute("var");
	}

    @Override
	public void apply(FaceletContext ctx, UIComponent parent) throws IOException {
        
        FacesContext facesContext = FacesContext.getCurrentInstance();
        
		Class type = getClassFromAttribute(typeTagAttribute, ctx);
		Map constants = getConstants(facesContext, type);

		// Create alias/var expression
		String var;
		if (varTagAttribute == null) {
			var = type.getSimpleName(); // fall back to class name
		} else {
			var = varTagAttribute.getValue(ctx);
		}

		if (var.charAt(0) != '#') {
			StringBuilder varBuilder = new StringBuilder();
			varBuilder.append("#{").append(var).append("}");

			var = varBuilder.toString();
		}

		// Assign constants to alias/var expression
		ELContext elContext = facesContext.getELContext();
		ExpressionFactory expressionFactory = facesContext.getApplication().getExpressionFactory();

		ValueExpression aliasValueExpression = expressionFactory.createValueExpression(elContext, var, Map.class);
		aliasValueExpression.setValue(elContext, constants);
	}

	/**
	 * Gets the {@link Class} from the {@link TagAttribute}.
	 * 
	 * @param attribute The {@link TagAttribute}.
	 * @param ctx The {@link FaceletContext}.
	 * @return The {@link Class}.
	 */
	protected Class getClassFromAttribute(TagAttribute attribute, FaceletContext ctx) {
		String type = attribute.getValue(ctx);

		try {
			return Class.forName(type, true, Thread.currentThread().getContextClassLoader());
		}
        catch (ClassNotFoundException e) {
			throw new FacesException("Class " + type + " not found.", e);
		}
	}

	/**
	 * Get all constants of the given {@link Class}.
	 *
     * @param facesContext The {@link FacesContext}.
	 * @param type The class which includes the constants.
	 * @return A {@link Map} with the constants.
	 */
	protected Map getConstants(FacesContext facesContext, Class type) {
        boolean cacheEnabled = facesContext.isProjectStage(ProjectStage.Production);
        Map, Map> cache =
                RequestContext.getCurrentInstance().getApplicationContext().getConstantsCacheMap();

		Map constants;

		if (cacheEnabled && cache.containsKey(type)) {
			constants = cache.get(type);
		}
        else {
			constants = Collections.unmodifiableMap(collectConstants(type));

            if (cacheEnabled) {
                cache.put(type, constants);
            }
		}

		return constants;
	}

	/**
	 * Collects all constants of the given {@link Class}.
	 *
	 * @param type The class which includes the constants.
	 * @return A {@link Map} with the found constants.
	 */
	protected Map collectConstants(Class type) {
		Map constants = new ConstantsHashMap(type);

		// Go through all the fields, and put static ones in a map.
		Field[] fields = type.getDeclaredFields();

        for (Field field : fields) {
            // Check to see if this is public static final. If not, it's not a constant.
            int modifiers = field.getModifiers();
            if (!Modifier.isFinal(modifiers) || !Modifier.isStatic(modifiers) || !Modifier.isPublic(modifiers)) {
                continue;
            }

            try {
                Object value = field.get(null); // null for static fields.
                constants.put(field.getName(), value);
            }
            catch (Exception e) {
                throw new FacesException("Could not get value of " + field.getName() + " in " + type.getName() + ".", e);
            }
        }

		return constants;
	}
}