org.omnifaces.resourcehandler.ViewResourceHandler Maven / Gradle / Ivy
/*
* Copyright OmniFaces
*
* 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
*
* https://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.omnifaces.resourcehandler;
import static java.lang.String.format;
import static org.omnifaces.util.FacesLocal.getContextAttribute;
import static org.omnifaces.util.FacesLocal.getRequest;
import static org.omnifaces.util.FacesLocal.getRequestServletPath;
import static org.omnifaces.util.FacesLocal.getResource;
import static org.omnifaces.util.Platform.getFacesServletRegistration;
import static org.omnifaces.util.Utils.isEmpty;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
import jakarta.faces.application.ResourceHandler;
import jakarta.faces.application.ViewResource;
import jakarta.faces.context.FacesContext;
import jakarta.faces.webapp.FacesServlet;
import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletRegistration;
import org.omnifaces.ApplicationListener;
import org.omnifaces.util.Faces;
import org.omnifaces.viewhandler.OmniViewHandler;
/**
* This {@link ResourceHandler} basically turns any concrete non-Facelets file into a Faces view, so that you can use EL expressions and even Faces components in them.
* The response content type will default to {@link Faces#getMimeType(String)} which is configureable in web.xml and overrideable via <f:view contentType="...">.
*
* Real world examples are /sitemap.xml and /robots.txt.
*
*
Installation
*
* To get it to run, this handler needs be registered as follows in faces-config.xml:
*
* <application>
* <resource-handler>org.omnifaces.resourcehandler.ViewResourceHandler</resource-handler>
* </application>
*
*
* To configure the Faces view resources, a {@value org.omnifaces.resourcehandler.ViewResourceHandler#PARAM_NAME_VIEW_RESOURCES}
* context parameter has to be provided wherein the view resources are specified as a comma separated string of context-relative URIs.
*
* Here is an example configuration:
*
* <context-param>
* <param-name>org.omnifaces.VIEW_RESOURCE_HANDLER_URIS</param-name>
* <param-value>/sitemap.xml, /products/sitemap.xml, /reviews/sitemap.xml, /robots.txt</param-value>
* </context-param>
*
*
* Wildcards in URIs are at the moment not supported.
*
* The {@link OmniViewHandler} will take care of rendering the view.
*
*
* @author Bauke Scholtz
* @since 3.10
* @see DefaultResourceHandler
* @see OmniViewHandler
*/
public class ViewResourceHandler extends DefaultResourceHandler {
/** The context parameter name to specify URIs to treat as Faces views. */
public static final String PARAM_NAME_VIEW_RESOURCES = "org.omnifaces.VIEW_RESOURCE_HANDLER_URIS";
private static final String ERROR_MISSING_FORWARD_SLASH = "View resource '%s' must start with a forward slash '/'.";
private static final String ERROR_UNKNOWN_VIEW_RESOURCE = "View resource '%s' does not exist.";
private static final Set VIEW_RESOURCES = new HashSet<>();
private static final ViewResource VIEW_RESOURCE = new ViewResource() {
@Override
public URL getURL() {
try {
FacesContext context = Faces.getContext();
return getResource(context, getRequestServletPath(context));
}
catch (MalformedURLException e) {
throw new IllegalStateException(e);
}
}
};
/**
* This will map the {@link FacesServlet} to the URIs specified in {@value org.omnifaces.resourcehandler.ViewResourceHandler#PARAM_NAME_VIEW_RESOURCES}
* context parameter.
* This is invoked by {@link ApplicationListener}, because the faces servlet registration has to be available for adding new mappings.
* @param servletContext The involved servlet context.
* @throws MalformedURLException When one of the URIs specified in context parameter is malformed.
*/
public static void addFacesServletMappingsIfNecessary(ServletContext servletContext) throws MalformedURLException {
String viewResourcesParam = servletContext.getInitParameter(PARAM_NAME_VIEW_RESOURCES);
if (isEmpty(viewResourcesParam)) {
return;
}
ServletRegistration facesServletRegistration = getFacesServletRegistration(servletContext);
if (facesServletRegistration != null) {
Collection existingMappings = facesServletRegistration.getMappings();
for (String viewResource : viewResourcesParam.split("\\s*,\\s*")) {
if (!viewResource.startsWith("/")) {
throw new IllegalArgumentException(format(ERROR_MISSING_FORWARD_SLASH, viewResource));
}
if (servletContext.getResource(viewResource) == null) {
throw new IllegalArgumentException(format(ERROR_UNKNOWN_VIEW_RESOURCE, viewResource));
}
VIEW_RESOURCES.add(viewResource);
if (!existingMappings.contains(viewResource)) {
facesServletRegistration.addMapping(viewResource);
}
}
}
}
/**
* Returns true if the current HTTP request is requesting for a view resource managed by this resource handler.
* @param context The involved faces context.
* @return true if the current HTTP request is requesting for a view resource managed by this resource handler.
*/
public static boolean isViewResourceRequest(FacesContext context) {
return !VIEW_RESOURCES.isEmpty() && getContextAttribute(context, ViewResourceHandler.class.getName(), () -> getRequest(context) != null && VIEW_RESOURCES.contains(getRequest(context).getServletPath()));
}
/**
* Creates a new instance of this view resource handler which wraps the given resource handler.
* @param wrapped The resource handler to be wrapped.
*/
public ViewResourceHandler(ResourceHandler wrapped) {
super(wrapped);
}
/**
* This override ensures that {@link Faces#getRequestServletPath()} is returned as concrete resource rather than the provided resourceName
* when the {@link #isViewResourceRequest(FacesContext)} returns true.
*/
@Override
public ViewResource createViewResource(FacesContext context, String resourceName) {
if (isViewResourceRequest(context)) {
return VIEW_RESOURCE;
}
else {
return super.createViewResource(context, resourceName);
}
}
}