facesutils.java

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/*
 * Copyright 2002-2004 the original author or authors.
 *
 * 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 de.mindmatters.faces;

import javax.faces.application.ViewHandler;
import javax.faces.context.FacesContext;
import javax.servlet.http.HttpServletRequest;

import org.springframework.util.Assert;

/**
 * Miscellaneous faces utility methods. Mainly for internal use within the
 * framework.
 * 
 * @author Andreas Kuhrwahl
 */
public final class FacesUtils {

    /**
     * Parameter name for the view id. The view id is mainly used as hidden
     * field to handle the <em>Restore View</em> phase of a submitted form
     * request.
     */
    public static final String VIEWID_PARAM = "view";

    /**
     * Parameter name for the transient flag. The transient flag is mainly used
     * as hidden field to handle the <em>Restore View</em> phase of a
     * post-submitted form request without any state.
     */
    public static final String TRANSIENT_PARAM = "transient";

    /**
     * Private Constructor - it's a static class.
     */
    private FacesUtils() {
    }

    /**
     * Try to guess if this is a postback request. We use a simple heuristic:
     * for HttpServletRequests, "POST" and "PUT" are postbacks. For anything
     * that isn't an HttpServletRequest, just guess that if there's a request
     * parameter, it's probably a postback.
     * 
     * @param context
     *            FacesContext that holds request information
     * @return <code>true</code> if it's a postback request <code>false</code>
     *         otherwise.
     */
    public static boolean isPostback(final FacesContext context) {
        Object requestObject = context.getExternalContext().getRequest();
        if (requestObject instanceof HttpServletRequest) {
            HttpServletRequest request = (HttpServletRequest) requestObject;
            String method = request.getMethod();
            if ("POST".equals(method) || "PUT".equals(method)) {
                return true;
            }
            return false;
        } else {
            return !context.getExternalContext().getRequestParameterMap()
                    .isEmpty();
        }
    }
    
    /**
     * Returns the value to use for the default extension if the webapp is using
     * url extension mapping.
     * 
     * @param context
     *            FacesContext that holds request information
     * @return The default suffix
     */
    public static String getDefaultSuffix(final FacesContext context) {
        String suffix = context.getExternalContext().getInitParameter(
                ViewHandler.DEFAULT_SUFFIX_PARAM_NAME);
        if (suffix == null) {
            suffix = ViewHandler.DEFAULT_SUFFIX;
        }
        return suffix;
    }

    /**
     * Encodes the view id of the current
     * {@link javax.faces.component.UIViewRoot}.
     * 
     * @param context
     *            FacesContext that holds request information
     * @return The encoded view id
     */
    public static String encodeViewId(final FacesContext context) {
        String viewId = context.getViewRoot().getViewId();
        viewId = viewId.substring(1, viewId.lastIndexOf('.'));
        return viewId;
    }

    /**
     * Decodes the view id of the current request.
     * 
     * @param context
     *            FacesContext that holds request information
     * @return The decoded view id
     */
    public static String decodeViewId(final FacesContext context) {
        String viewId = (String) context.getExternalContext()
                .getRequestParameterMap().get(FacesUtils.VIEWID_PARAM);
        if (viewId != null) {
            viewId = '/' + viewId + getDefaultSuffix(context);
        }
        return viewId;
    }

    /**
     * Checks whether the string <code>value</code> is a value binding
     * compatible string or not.
     * 
     * @param value
     *            the string to check
     * @return <code>true</code> if <code>value</code> is a value binding
     *         compatible string else <code>false</code>
     */
    public static boolean isValueReference(final String value) {
        Assert.notNull(value);
        return value.indexOf("#{") != -1
                && value.indexOf("#{") < value.indexOf('}');
    }

}