io.wcm.handler.url.rewriter.impl.UrlExternalizerTransformer.java Source code

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Here is the source code for io.wcm.handler.url.rewriter.impl.UrlExternalizerTransformer.java

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/*
 * #%L
 * wcm.io
 * %%
 * Copyright (C) 2014 wcm.io
 * %%
 * 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.
 * #L%
 */
package io.wcm.handler.url.rewriter.impl;

import io.wcm.handler.url.UrlHandler;

import org.apache.cocoon.xml.sax.AbstractSAXPipe;
import org.apache.cocoon.xml.sax.AttributesImpl;
import org.apache.commons.lang3.StringEscapeUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.sling.rewriter.ProcessingComponentConfiguration;
import org.apache.sling.rewriter.ProcessingContext;
import org.apache.sling.rewriter.Transformer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;

/**
 * HTML transformer that rewrites URLs in certain HTML element attributes.
 */
class UrlExternalizerTransformer extends AbstractSAXPipe implements Transformer {

    private UrlExternalizerTransformerConfig transformerConfig;
    private UrlHandler urlHandler;

    private static final Logger log = LoggerFactory.getLogger(UrlExternalizerTransformer.class.getName());

    @Override
    public void init(ProcessingContext pipelineContext, ProcessingComponentConfiguration config) {
        log.trace("Initialize UrlExternalizerTransformer with config: {}", config.getConfiguration());
        transformerConfig = new UrlExternalizerTransformerConfig(config.getConfiguration());
        urlHandler = pipelineContext.getRequest().adaptTo(UrlHandler.class);
    }

    @Override
    public void startElement(String nsUri, String name, String raw, Attributes attrs) throws SAXException {

        // check if for this element an attribute for rewriting is configured
        String rewriteAttr = transformerConfig.getElementAttributeNames().get(name);
        if (rewriteAttr == null) {
            log.trace("Rewrite element {}: Skip - No rewrite attribute configured.", name);
            super.startElement(nsUri, name, raw, attrs);
            return;
        }

        // validate URL handler
        if (urlHandler == null) {
            log.warn("Rewrite element {}: Skip - Unable to get URL handler/Integrator handler instance.", name);
            super.startElement(nsUri, name, raw, attrs);
            return;
        }

        // check if attribute exists
        int attributeIndex = attrs.getIndex(rewriteAttr);
        if (attributeIndex < 0) {
            log.trace("Rewrite element {}: Skip - Attribute does not exist: {}", name, rewriteAttr);
            super.startElement(nsUri, name, raw, attrs);
            return;
        }

        // rewrite URL
        String url = attrs.getValue(attributeIndex);
        if (StringUtils.isEmpty(url)) {
            log.trace("Rewrite element {}: Skip - URL is empty.", name);
            super.startElement(nsUri, name, raw, attrs);
            return;
        }

        // remove escaping
        url = StringEscapeUtils.unescapeHtml4(url);

        // externalize URL (if it is not already externalized)
        String rewrittenUrl = urlHandler.get(url).buildExternalResourceUrl();

        if (StringUtils.equals(url, rewrittenUrl)) {
            log.debug("Rewrite element {}: Skip - URL is already externalized: {}", name, url);
            super.startElement(nsUri, name, raw, attrs);
            return;
        }

        // set new attribute value
        log.debug("Rewrite element {}: Rewrite URL {} to {}", name, url, rewrittenUrl);
        AttributesImpl newAttrs = new AttributesImpl(attrs);
        newAttrs.setValue(attributeIndex, rewrittenUrl);
        super.startElement(nsUri, name, raw, newAttrs);
    }

    @Override
    public void dispose() {
        // nothing to do
    }

}