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.nifi.web; import com.ibm.icu.text.CharsetDetector; import com.ibm.icu.text.CharsetMatch; import java.io.BufferedInputStream; import java.io.IOException; import java.io.InputStream; import java.net.URI; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.codec.binary.Base64; import org.apache.commons.io.IOUtils; import org.apache.commons.lang3.StringUtils; import org.apache.nifi.authorization.AccessDeniedException; import org.apache.nifi.stream.io.StreamUtils; import org.apache.nifi.web.ViewableContent.DisplayMode; import org.apache.tika.detect.DefaultDetector; import org.apache.tika.io.TikaInputStream; import org.apache.tika.metadata.Metadata; import org.apache.tika.mime.MediaType; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Controller servlet for viewing content. This is responsible for generating * the markup for the header and footer of the page. Included in that is the * combo that allows the user to choose how they wait to view the data * (original, formatted, hex). If a data viewer is registered for the detected * content type, it will include the markup it generates in the response. */ public class ContentViewerController extends HttpServlet { private static final Logger logger = LoggerFactory.getLogger(ContentViewerController.class); // 1.5kb - multiple of 12 (3 bytes = 4 base 64 encoded chars) private final static int BUFFER_LENGTH = 1536; /** * Gets the content and defers to registered viewers to generate the markup. * * @param request servlet request * @param response servlet response * @throws ServletException if a servlet-specific error occurs * @throws IOException if an I/O error occurs */ @Override protected void doGet(final HttpServletRequest request, final HttpServletResponse response) throws ServletException, IOException { // specify the charset in a response header response.addHeader("Content-Type", "text/html; charset=UTF-8"); // get the content final ServletContext servletContext = request.getServletContext(); final ContentAccess contentAccess = (ContentAccess) servletContext.getAttribute("nifi-content-access"); final ContentRequestContext contentRequest; try { contentRequest = getContentRequest(request); } catch (final Exception e) { request.setAttribute("title", "Error"); request.setAttribute("messages", "Unable to interpret content request."); // forward to the error page final ServletContext viewerContext = servletContext.getContext("/nifi"); viewerContext.getRequestDispatcher("/message").forward(request, response); return; } if (contentRequest.getDataUri() == null) { request.setAttribute("title", "Error"); request.setAttribute("messages", "The data reference must be specified."); // forward to the error page final ServletContext viewerContext = servletContext.getContext("/nifi"); viewerContext.getRequestDispatcher("/message").forward(request, response); return; } // get the content final DownloadableContent downloadableContent; try { downloadableContent = contentAccess.getContent(contentRequest); } catch (final ResourceNotFoundException rnfe) { request.setAttribute("title", "Error"); request.setAttribute("messages", "Unable to find the specified content"); // forward to the error page final ServletContext viewerContext = servletContext.getContext("/nifi"); viewerContext.getRequestDispatcher("/message").forward(request, response); return; } catch (final AccessDeniedException ade) { request.setAttribute("title", "Access Denied"); request.setAttribute("messages", "Unable to approve access to the specified content: " + ade.getMessage()); // forward to the error page final ServletContext viewerContext = servletContext.getContext("/nifi"); viewerContext.getRequestDispatcher("/message").forward(request, response); return; } catch (final Exception e) { request.setAttribute("title", "Error"); request.setAttribute("messages", "An unexpected error has occurred: " + e.getMessage()); // forward to the error page final ServletContext viewerContext = servletContext.getContext("/nifi"); viewerContext.getRequestDispatcher("/message").forward(request, response); return; } // determine how we want to view the data String mode = request.getParameter("mode"); // if the name isn't set, use original if (mode == null) { mode = DisplayMode.Original.name(); } // determine the display mode final DisplayMode displayMode; try { displayMode = DisplayMode.valueOf(mode); } catch (final IllegalArgumentException iae) { request.setAttribute("title", "Error"); request.setAttribute("messages", "Invalid display mode: " + mode); // forward to the error page final ServletContext viewerContext = servletContext.getContext("/nifi"); viewerContext.getRequestDispatcher("/message").forward(request, response); return; } // buffer the content to support resetting in case we need to detect the content type or char encoding try (final BufferedInputStream bis = new BufferedInputStream(downloadableContent.getContent());) { final String mimeType; final String normalizedMimeType; // when standalone and we don't know the type is null as we were able to directly access the content bypassing the rest endpoint, // when clustered and we don't know the type set to octet stream since the content was retrieved from the node's rest endpoint if (downloadableContent.getType() == null || StringUtils .startsWithIgnoreCase(downloadableContent.getType(), MediaType.OCTET_STREAM.toString())) { // attempt to detect the content stream if we don't know what it is () final DefaultDetector detector = new DefaultDetector(); // create the stream for tika to process, buffered to support reseting final TikaInputStream tikaStream = TikaInputStream.get(bis); // provide a hint based on the filename final Metadata metadata = new Metadata(); metadata.set(Metadata.RESOURCE_NAME_KEY, downloadableContent.getFilename()); // Get mime type final MediaType mediatype = detector.detect(tikaStream, metadata); mimeType = mediatype.toString(); } else { mimeType = downloadableContent.getType(); } // Extract only mime type and subtype from content type (anything after the first ; are parameters) // Lowercase so subsequent code does not need to implement case insensitivity normalizedMimeType = mimeType.split(";", 2)[0].toLowerCase(); // add attributes needed for the header request.setAttribute("filename", downloadableContent.getFilename()); request.setAttribute("contentType", mimeType); // generate the header request.getRequestDispatcher("/WEB-INF/jsp/header.jsp").include(request, response); // remove the attributes needed for the header request.removeAttribute("filename"); request.removeAttribute("contentType"); // generate the markup for the content based on the display mode if (DisplayMode.Hex.equals(displayMode)) { final byte[] buffer = new byte[BUFFER_LENGTH]; final int read = StreamUtils.fillBuffer(bis, buffer, false); // trim the byte array if necessary byte[] bytes = buffer; if (read != buffer.length) { bytes = new byte[read]; System.arraycopy(buffer, 0, bytes, 0, read); } // convert bytes into the base 64 bytes final String base64 = Base64.encodeBase64String(bytes); // defer to the jsp request.setAttribute("content", base64); request.getRequestDispatcher("/WEB-INF/jsp/hexview.jsp").include(request, response); } else { // lookup a viewer for the content final String contentViewerUri = servletContext.getInitParameter(normalizedMimeType); // handle no viewer for content type if (contentViewerUri == null) { request.getRequestDispatcher("/WEB-INF/jsp/no-viewer.jsp").include(request, response); } else { // create a request attribute for accessing the content request.setAttribute(ViewableContent.CONTENT_REQUEST_ATTRIBUTE, new ViewableContent() { @Override public InputStream getContentStream() { return bis; } @Override public String getContent() throws IOException { // detect the charset final CharsetDetector detector = new CharsetDetector(); detector.setText(bis); detector.enableInputFilter(true); final CharsetMatch match = detector.detect(); // ensure we were able to detect the charset if (match == null) { throw new IOException("Unable to detect character encoding."); } // convert the stream using the detected charset return IOUtils.toString(bis, match.getName()); } @Override public ViewableContent.DisplayMode getDisplayMode() { return displayMode; } @Override public String getFileName() { return downloadableContent.getFilename(); } @Override public String getContentType() { return normalizedMimeType; } @Override public String getRawContentType() { return mimeType; } }); try { // generate the content final ServletContext viewerContext = servletContext.getContext(contentViewerUri); viewerContext.getRequestDispatcher("/view-content").include(request, response); } catch (final Exception e) { String message = e.getMessage() != null ? e.getMessage() : e.toString(); message = "Unable to generate view of data: " + message; // log the error logger.error(message); if (logger.isDebugEnabled()) { logger.error(StringUtils.EMPTY, e); } // populate the request attributes request.setAttribute("title", "Error"); request.setAttribute("messages", message); // forward to the error page final ServletContext viewerContext = servletContext.getContext("/nifi"); viewerContext.getRequestDispatcher("/message").forward(request, response); return; } // remove the request attribute request.removeAttribute(ViewableContent.CONTENT_REQUEST_ATTRIBUTE); } } // generate footer request.getRequestDispatcher("/WEB-INF/jsp/footer.jsp").include(request, response); } } /** * @param request request * @return Get the content request context based on the specified request */ private ContentRequestContext getContentRequest(final HttpServletRequest request) { final String ref = request.getParameter("ref"); final String clientId = request.getParameter("clientId"); final URI refUri = URI.create(ref); final String query = refUri.getQuery(); String rawClusterNodeId = null; if (query != null) { final String[] queryParameters = query.split("&"); for (int i = 0; i < queryParameters.length; i++) { if (queryParameters[0].startsWith("clusterNodeId=")) { rawClusterNodeId = StringUtils.substringAfterLast(queryParameters[0], "clusterNodeId="); } } } final String clusterNodeId = rawClusterNodeId; return new ContentRequestContext() { @Override public String getDataUri() { return ref; } @Override public String getClusterNodeId() { return clusterNodeId; } @Override public String getClientId() { return clientId; } @Override public String getProxiedEntitiesChain() { return null; } }; } }