org.apache.shindig.gadgets.rewrite.ResourceMutateVisitor.java Source code

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Here is the source code for org.apache.shindig.gadgets.rewrite.ResourceMutateVisitor.java

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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.shindig.gadgets.rewrite;

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
import org.apache.commons.lang.StringUtils;
import org.apache.shindig.common.Pair;
import org.apache.shindig.common.uri.Uri;
import org.apache.shindig.gadgets.Gadget;
import org.w3c.dom.Attr;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

import java.util.Collection;
import java.util.List;
import java.util.Map;

/**
 * Abstract visitor that walks over html tags as specified by
 * {@code resourceTags} and prepares list of html tag nodes whose uri
 * attributes can be mutated.
 * Implementations can override {@link #mutateUris} for uses cases like
 * proxying resources, making url's absolute, prefetching images etc.
 *
 * TODO: Refactor AbsolutePathReferenceVisitor to extend ResourceMutateVisitor.
 *
 * @since 2.0.0
 */
public abstract class ResourceMutateVisitor implements DomWalker.Visitor {
    /**
     * Enum for resource tags and associated attributes that should be mutated.
     */
    public enum Tags {
        // Javascript resources requested by the current page.
        SCRIPT(ImmutableMap.of("script", "src")),

        // Css stylesheet resources requested by the current page.
        STYLESHEET(ImmutableMap.of("link", "href")),

        // Other embedded resources requested on the same page.
        EMBEDDED_IMAGES(ImmutableMap.of("body", "background", "img", "src", "input", "src")),

        // All resources that possibly be rewritten. Useful for testing.
        ALL_RESOURCES(ImmutableMap.<String, String>builder().putAll(SCRIPT.getResourceTags())
                .putAll(STYLESHEET.getResourceTags()).putAll(EMBEDDED_IMAGES.getResourceTags()).build());

        private Map<String, String> resourceTags;

        private Tags(Map<String, String> resourceTags) {
            this.resourceTags = resourceTags;
        }

        public Map<String, String> getResourceTags() {
            return resourceTags;
        }
    }

    // Map of tag name to attribute of resources to rewrite.
    protected final Map<String, String> resourceTags;
    protected final ContentRewriterFeature.Config featureConfig;

    public ResourceMutateVisitor(ContentRewriterFeature.Config featureConfig, Tags... resourceTags) {
        this.featureConfig = featureConfig;

        Map<String, String> rTags = Maps.newHashMap();
        for (Tags r : resourceTags) {
            rTags.putAll(r.getResourceTags());
        }
        this.resourceTags = ImmutableMap.<String, String>builder().putAll(rTags).build();
    }

    /**
     * {@inheritDoc}
     */
    public VisitStatus visit(Gadget gadget, Node node) throws RewritingException {
        String nodeName = node.getNodeName().toLowerCase();
        if (node.getNodeType() == Node.ELEMENT_NODE && resourceTags.containsKey(nodeName)
                && featureConfig.shouldRewriteTag(nodeName)) {
            if ("link".equals(nodeName)) {
                // Rewrite link only when it is for css.
                String type = ((Element) node).getAttribute("type");
                String rel = ((Element) node).getAttribute("rel");
                if (!"stylesheet".equalsIgnoreCase(rel) || !"text/css".equalsIgnoreCase(type)) {
                    return VisitStatus.BYPASS;
                }
            }

            Attr attr = (Attr) node.getAttributes().getNamedItem(resourceTags.get(nodeName));
            if (attr != null) {
                String urlValue = attr.getValue();
                if (!StringUtils.isEmpty(urlValue) && featureConfig.shouldRewriteURL(urlValue)) {
                    return VisitStatus.RESERVE_NODE;
                }
            }
        }
        return VisitStatus.BYPASS;
    }

    /**
     * {@inheritDoc}
     */
    public boolean revisit(Gadget gadget, List<Node> nodes) throws RewritingException {
        Collection<Pair<Node, Uri>> proxiedUris = mutateUris(gadget, nodes);

        boolean mutated = false;
        for (Pair<Node, Uri> proxyPair : proxiedUris) {
            if (proxyPair.two == null) {
                continue;
            }
            Element element = (Element) proxyPair.one;
            String nodeName = element.getNodeName().toLowerCase();
            element.setAttribute(resourceTags.get(nodeName), proxyPair.two.toString());
            mutated = true;
        }

        return mutated;
    }

    // Mutate the list of nodes reserved by revisit().
    protected abstract Collection<Pair<Node, Uri>> mutateUris(Gadget gadget, Collection<Node> nodes);
}