Java tutorial
/* * See the NOTICE file distributed with this work for additional * information regarding copyright ownership. * * This is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * This software is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this software; if not, write to the Free * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA * 02110-1301 USA, or see the FSF site: http://www.fsf.org. */ package org.xwiki.extension.xar.internal.job.diff; import java.io.IOException; import java.io.InputStream; import java.util.Arrays; import java.util.Collections; import java.util.List; import javax.inject.Singleton; import org.apache.commons.io.IOUtils; import org.apache.commons.lang3.exception.ExceptionUtils; import org.xwiki.component.annotation.Component; import org.xwiki.diff.display.UnifiedDiffBlock; import org.xwiki.extension.xar.job.diff.DocumentUnifiedDiff; import org.xwiki.extension.xar.job.diff.DocumentVersionReference; import org.xwiki.extension.xar.job.diff.EntityUnifiedDiff; import org.xwiki.model.reference.AttachmentReference; import com.xpn.xwiki.XWikiContext; import com.xpn.xwiki.doc.XWikiAttachment; /** * Computes the differences, in unified format, between two versions of an attachment. * * @version $Id: c02a556b0ad331d7c24a4b48da26ba60abdff585 $ * @since 7.0RC1 */ @Component(roles = AttachmentUnifiedDiffBuilder.class) @Singleton public class AttachmentUnifiedDiffBuilder extends AbstractUnifiedDiffBuilder { /** * The list of media type patterns that match text files. */ private static final List<String> TEXT_MEDIA_TYPE_PATTERNS = Arrays.asList("text/", "application/xml", "application/javascript", "application/ecmascript", "application/json", "application/x-sh", "+xml"); /** * Show content differences only for text files under 50KB. */ private static final long TEXT_FILE_SIZE_LIMIT = 50000; /** * Computes the differences, in unified format, between two versions of an attachment and adds the result to the * given {@link DocumentUnifiedDiff}. * * @param previousAttachment the previous version of the attachment * @param nextAttachment the next version of the attachment * @param documentDiff where to add the differences */ public void addAttachmentDiff(XWikiAttachment previousAttachment, XWikiAttachment nextAttachment, DocumentUnifiedDiff documentDiff) { AttachmentReference previousReference = getAttachmentVersionReference(previousAttachment, documentDiff.getPreviousReference()); AttachmentReference nextReference = getAttachmentVersionReference(nextAttachment, documentDiff.getNextReference()); EntityUnifiedDiff<AttachmentReference> attachmentDiff = new EntityUnifiedDiff<>(previousReference, nextReference); if ((previousAttachment == null || isSmallTextFile(previousAttachment)) && (nextAttachment == null || isSmallTextFile(nextAttachment))) { // Compute content differences. maybeAddDiff(attachmentDiff, CONTENT, getContentAsString(previousAttachment), getContentAsString(nextAttachment)); } else { // The size difference is useful when the content difference is not shown. maybeAddDiff(attachmentDiff, "size", previousAttachment == null ? null : previousAttachment.getLongSize(), nextAttachment == null ? null : nextAttachment.getLongSize()); if (attachmentDiff.isEmpty() && !contentEquals(previousAttachment, nextAttachment)) { // If the files have the same size but the content is different then show an empty list. attachmentDiff.put(CONTENT, Collections.<UnifiedDiffBlock<String, Character>>emptyList()); } } if (attachmentDiff.size() > 0) { documentDiff.getAttachmentDiffs().add(attachmentDiff); } } private AttachmentReference getAttachmentVersionReference(XWikiAttachment attachment, DocumentVersionReference documentVersionReference) { return attachment == null ? null : new AttachmentReference(attachment.getFilename(), documentVersionReference); } private boolean isSmallTextFile(XWikiAttachment attachment) { if (attachment != null && attachment.getLongSize() < TEXT_FILE_SIZE_LIMIT) { String mediaType = attachment.getMimeType(xcontextProvider.get()); for (String mediaTypePattern : TEXT_MEDIA_TYPE_PATTERNS) { if (mediaType.equals(mediaTypePattern) || mediaType.startsWith(mediaTypePattern) || mediaType.endsWith(mediaTypePattern)) { return true; } } } return false; } private boolean contentEquals(XWikiAttachment previousAttachment, XWikiAttachment nextAttachment) { if (previousAttachment == null || nextAttachment == null) { return previousAttachment == nextAttachment; } else { XWikiContext xcontext = this.xcontextProvider.get(); InputStream previousContent = null; InputStream nextContent = null; try { previousContent = previousAttachment.getContentInputStream(xcontext); nextContent = nextAttachment.getContentInputStream(xcontext); return IOUtils.contentEquals(previousContent, nextContent); } catch (Exception e) { this.logger.warn("Failed to compare the content of attachment [{}]. Root cause: {}", previousAttachment.getFilename(), ExceptionUtils.getRootCauseMessage(e)); return false; } finally { try { if (previousContent != null) { previousContent.close(); } if (nextContent != null) { nextContent.close(); } } catch (IOException e) { // Ignore. } } } } private String getContentAsString(XWikiAttachment attachment) { try { return attachment == null ? null : IOUtils.toString(attachment.getContentInputStream(this.xcontextProvider.get())); } catch (Exception e) { this.logger.warn("Failed to read the content of attachment [{}]. Root cause: {}", attachment.getFilename(), ExceptionUtils.getRootCauseMessage(e)); return null; } } }