org.apache.myfaces.renderkit.html.util.MyFacesResourceHandler Maven / Gradle / Ivy

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JSF components and utilities that can be used with any JSF implementation. This library is based on the JSF1.1 version of Tomahawk, but with minor source code and build changes to take advantage of JSF2.1 features. A JSF2.1 implementation is required to use this version of the Tomahawk library.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.myfaces.renderkit.html.util;

import javax.faces.context.FacesContext;

/**
 * A ResourceHandler which always generates URLs that trigger the
 * MyfacesResourceLoader to load resources from the classpath
 * relative to some Tomahawk class.
 * 
 * This is intended to support loading of Tomahawk resources only;
 * applications which wish to use the Tomahawk AddResources framework
 * for loading resources from elsewhere should implement their own
 * ResourceHandler class.
 * 
 * @author Mathias Broekelmann
 */
public class MyFacesResourceHandler implements ResourceHandler
{
    private final Class _myfacesCustomComponent;
    private final String _resource;

    /**
     * Constructor.
     * 
     * @param myfacesCustomComponent is a class that must be in package
     *   org.apache.myfaces.custom. The resource to be served will be
     *   located relative to this class in the classpath. Note that code
     *   wishing to serve resources from other locations in the classpath
     *   must write a custom ResourceHandler implementation.
     *   
     * @param resourceName is the name of a file that can be found in dir
     *  "resource/{resourceName} relative to the location of the specified
     *  component class in the classpath. Because the resource is always
     *  relative to a class file, it must never begin with a slash. 
     */
    public MyFacesResourceHandler(Class myfacesCustomComponent, String resourceName)
    {
        validateCustomComponent(myfacesCustomComponent);
        _myfacesCustomComponent = myfacesCustomComponent;
        _resource = resourceName;
    }
    
    /**
     * Return a Class object which can decode the url generated by this
     * class in the getResourceUri method and use that info to locate
     * the resource data represented by this object.
     * 
     * @see ResourceHandler#getResourceLoaderClass()
     */
    public Class getResourceLoaderClass()
    {
        return MyFacesResourceLoader.class;
    }

    /**
     * Verify that the base class for the resource lookup is in the 
     * org.apache.myfaces.custom package.
     * 
     * @param myfacesCustomComponent is the base component for the lookup.
     * @throws IllegalArgumentException if the class is not in the expected package. 
     */
    protected void validateCustomComponent(Class myfacesCustomComponent)
    {
        if (!myfacesCustomComponent.getName().startsWith(
                MyFacesResourceLoader.ORG_APACHE_MYFACES_CUSTOM + "."))
        {
            throw new IllegalArgumentException(
                    "expected a myfaces custom component class in package "
                            + MyFacesResourceLoader.ORG_APACHE_MYFACES_CUSTOM);
        }
    }

    /**
     * Return a URL that the browser can later submit to retrieve the resource
     * handled by this instance.
     * 

     * The emitted URL is of form:
     * 
     *   {partial.class.name}/{resourceName}
     * 
     * where partial.class.name is the name of the base class specified in the
     * constructor, and resourceName is the resource specified in the constructor.
     * 
     * @see org.apache.myfaces.shared.renderkit.html.util.ResourceHandler#getResourceUri(javax.faces.context.FacesContext)
     */
    public String getResourceUri(FacesContext context)
    {
        String className = _myfacesCustomComponent.getName();
        StringBuffer sb = new StringBuffer();
        sb.append(className.substring(
            MyFacesResourceLoader.ORG_APACHE_MYFACES_CUSTOM.length() + 1));
        sb.append("/");
        if (_resource != null)
        {
            if (_resource.startsWith("/"))
            {
                throw new IllegalArgumentException(
                    "Tomahawk resources are always relative to the associated class." +
                    " Absolute resource paths are not allowed: " + _resource);
            }
            sb.append(_resource);
        }
        return sb.toString();
    }
}