Java tutorial
/* * 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.annotations.VisibleForTesting; import com.google.common.collect.ImmutableMap; import com.google.inject.Inject; import org.apache.commons.lang.StringUtils; import org.apache.shindig.common.uri.Uri; import org.apache.shindig.gadgets.Gadget; import org.apache.shindig.gadgets.rewrite.DomWalker.Visitor; import org.w3c.dom.Attr; import org.w3c.dom.Document; import org.w3c.dom.NamedNodeMap; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.w3c.dom.Element; import java.util.HashMap; import java.util.List; import java.util.Map; /** * Visitor that resolves relative paths relative to the * base tag (only if present) / current page url and marks urls as absolute. * * @since 2.0.0 */ public class AbsolutePathReferenceVisitor implements Visitor { public enum Tags { // Resources which would be fetched by the browser when rendering the page. RESOURCES(ImmutableMap.<String, String>builder().put("body", "background").put("img", "src") .put("input", "src").put("link", "href").put("script", "src").build()), // Hyperlinks that the user clicks on to navigate pages. HYPERLINKS(ImmutableMap.<String, String>builder().put("a", "href").put("area", "href").put("q", "cite") .build()); Map<String, String> resourceTags; private Tags(Map<String, String> resourceTags) { this.resourceTags = resourceTags; } public Map<String, String> getResourceTags() { return resourceTags; } } // Map of tag name -> attribute type describing uris to make absolute. private final Map<String, String> tagsToMakeAbsolute; @Inject public AbsolutePathReferenceVisitor(Tags... resourceTags) { Map<String, String> tagsToMakeAbsolute = new HashMap<String, String>(); for (Tags r : resourceTags) { tagsToMakeAbsolute.putAll(r.getResourceTags()); } this.tagsToMakeAbsolute = tagsToMakeAbsolute; } // @Override public VisitStatus visit(Gadget gadget, Node node) throws RewritingException { Attr nodeAttr = getUriAttributeFromNode(node, tagsToMakeAbsolute); if (nodeAttr != null) { try { Uri nodeUri = Uri.parse(nodeAttr.getValue()); Uri baseUri = getBaseResolutionUri(gadget, node); Uri resolved = baseUri.resolve(nodeUri); if (!resolved.equals(nodeUri)) { nodeAttr.setValue(resolved.toString()); return VisitStatus.MODIFY; } } catch (Uri.UriException e) { // UriException on illegal input. Ignore. } } return VisitStatus.BYPASS; } // @Override public boolean revisit(Gadget gadget, List<Node> node) throws RewritingException { // Modification happens immediately. return false; } /** * Returns the uri attribute for the given node by looking up the * tag name -> uri attribute map. * NOTE: This function returns the node attribute only if the attribute has a * non empty value. * @param node The node to get uri attribute for. * @param resourceTags Map from tag name -> uri attribute name. * @return Uri attribute for the node. */ public static Attr getUriAttributeFromNode(Node node, Map<String, String> resourceTags) { String nodeName = node.getNodeName().toLowerCase(); if (node.getNodeType() == Node.ELEMENT_NODE && resourceTags.containsKey(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 null; } } Attr attr = (Attr) node.getAttributes().getNamedItem(resourceTags.get(nodeName)); String nodeUri = attr != null ? attr.getValue() : null; if (!StringUtils.isEmpty(nodeUri)) { return attr; } } return null; } /** * Returns the uri to resolve any relative url on the current page to. * This is equal to the base uri (in case the page has one) or the current * page uri. * @param gadget The gadget (container for page) being processed. * @param node The current node being processed. * @return The uri to resolve non absolute uri's relative to. */ private Uri getBaseResolutionUri(Gadget gadget, Node node) { Uri pageUri = gadget.getSpec().getUrl(); Uri baseUri = getBaseUri(node.getOwnerDocument()); return baseUri != null ? baseUri : pageUri; } /** * Returns the base uri of the given document. * Base uri is specified as <base href="..."> * @param doc The document. * @return Base uri of the document. */ @VisibleForTesting Uri getBaseUri(Document doc) { String baseHref = getBaseHref(doc); if (baseHref != null) { try { return Uri.parse(baseHref); } catch (Uri.UriException e) { // Ignore. } } return null; } /** * Returns href value of the base tag. * @param doc The document to process. * @return Value of href attribute of the base tag. */ @VisibleForTesting String getBaseHref(Document doc) { NodeList list = doc.getElementsByTagName("base"); if (list.getLength() == 0) { return null; } NamedNodeMap nodeMap = list.item(0).getAttributes(); if (nodeMap == null) { return null; } Attr attr = (Attr) nodeMap.getNamedItem("href"); return attr != null ? attr.getValue() : null; } }