gitiles-servlet/src/main/java/com/google/gitiles/BaseServlet.java - gitiles - Rivoreo Source Code Repositories

 // Copyright 2012 Google Inc. All Rights Reserved.
 //
 // 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.

 package com.google.gitiles;

 import static com.google.common.base.MoreObjects.firstNonNull;
 import static com.google.gitiles.FormatType.DEFAULT;
 import static com.google.gitiles.FormatType.HTML;
 import static com.google.gitiles.FormatType.JSON;
 import static com.google.gitiles.FormatType.TEXT;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static javax.servlet.http.HttpServletResponse.SC_BAD_REQUEST;
 import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
 import static javax.servlet.http.HttpServletResponse.SC_OK;
 import static org.eclipse.jgit.util.HttpSupport.ENCODING_GZIP;

 import com.google.common.base.Joiner;
 import com.google.common.base.Optional;
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Maps;
 import com.google.common.net.HttpHeaders;
 import com.google.gson.FieldNamingPolicy;
 import com.google.gson.GsonBuilder;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.io.Writer;
 import java.lang.reflect.Type;
 import java.util.Map;
 import java.util.List;
 import java.util.regex.Pattern;
 import java.util.zip.GZIPOutputStream;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import org.joda.time.Instant;

 /** Base servlet class for Gitiles servlets that serve Soy templates. */
 public abstract class BaseServlet extends HttpServlet {
   private static final long serialVersionUID = 1L;
   private static final String ACCESS_ATTRIBUTE = BaseServlet.class.getName() + "/GitilesAccess";
   private static final String DATA_ATTRIBUTE = BaseServlet.class.getName() + "/Data";
   private static final String STREAMING_ATTRIBUTE = BaseServlet.class.getName() + "/Streaming";

   static void setNotCacheable(HttpServletResponse res) {
     res.setHeader(HttpHeaders.CACHE_CONTROL, "no-cache, no-store, max-age=0, must-revalidate");
     res.setHeader(HttpHeaders.PRAGMA, "no-cache");
     res.setHeader(HttpHeaders.EXPIRES, "Mon, 01 Jan 1990 00:00:00 GMT");
     res.setDateHeader(HttpHeaders.DATE, new Instant().getMillis());
   }

   public static BaseServlet notFoundServlet() {
     return new BaseServlet(null, null) {
       private static final long serialVersionUID = 1L;

       @Override
       public void service(HttpServletRequest req, HttpServletResponse res) {
         res.setStatus(SC_NOT_FOUND);
       }
     };
   }

   public static Map<String, String> menuEntry(String text, String url) {
     if (url != null) {
       return ImmutableMap.of("text", text, "url", url);
     }
     return ImmutableMap.of("text", text);
   }

   public static boolean isStreamingResponse(HttpServletRequest req) {
     return firstNonNull((Boolean) req.getAttribute(STREAMING_ATTRIBUTE), false);
   }

   protected static ArchiveFormat getArchiveFormat(GitilesAccess access) throws IOException {
     return ArchiveFormat.getDefault(access.getConfig());
   }

   /**
    * Put a value into a request's Soy data map.
    *
    * @param req in-progress request.
    * @param key key.
    * @param value Soy data value.
    */
   public static void putSoyData(HttpServletRequest req, String key, Object value) {
     getData(req).put(key, value);
   }

   @Override
   protected void doGet(HttpServletRequest req, HttpServletResponse res)
       throws IOException, ServletException {
     Optional<FormatType> format = getFormat(req);
     if (!format.isPresent()) {
       res.sendError(SC_BAD_REQUEST);
       return;
     }
     switch (format.get()) {
       case HTML:
         doGetHtml(req, res);
         break;
       case TEXT:
         doGetText(req, res);
         break;
       case JSON:
         doGetJson(req, res);
         break;
       case DEFAULT:
       default:
         res.sendError(SC_BAD_REQUEST);
         break;
     }
   }

   protected Optional<FormatType> getFormat(HttpServletRequest req) {
     Optional<FormatType> format = FormatType.getFormatType(req);
     if (format.isPresent() && format.get() == DEFAULT) {
       return Optional.of(getDefaultFormat(req));
     }
     return format;
   }

   /**
    * @param req in-progress request.
    * @return the default {@link FormatType} used when {@code ?format=} is not specified.
    */
   protected FormatType getDefaultFormat(HttpServletRequest req) {
     return HTML;
   }

   /**
    * Handle a GET request when the requested format type was HTML.
    *
    * @param req in-progress request.
    * @param res in-progress response.
    */
   protected void doGetHtml(HttpServletRequest req, HttpServletResponse res) throws IOException {
     res.sendError(SC_BAD_REQUEST);
   }

   /**
    * Handle a GET request when the requested format type was plain text.
    *
    * @param req in-progress request.
    * @param res in-progress response.
    */
   protected void doGetText(HttpServletRequest req, HttpServletResponse res) throws IOException {
     res.sendError(SC_BAD_REQUEST);
   }

   /**
    * Handle a GET request when the requested format type was JSON.
    *
    * @param req in-progress request.
    * @param res in-progress response.
    */
   protected void doGetJson(HttpServletRequest req, HttpServletResponse res) throws IOException {
     res.sendError(SC_BAD_REQUEST);
   }

   protected static Map<String, Object> getData(HttpServletRequest req) {
     @SuppressWarnings("unchecked")
     Map<String, Object> data = (Map<String, Object>) req.getAttribute(DATA_ATTRIBUTE);
     if (data == null) {
       data = Maps.newHashMap();
       req.setAttribute(DATA_ATTRIBUTE, data);
     }
     return data;
   }

   protected final Renderer renderer;
   private final GitilesAccess.Factory accessFactory;

   protected BaseServlet(Renderer renderer, GitilesAccess.Factory accessFactory) {
     this.renderer = renderer;
     this.accessFactory = accessFactory;
   }

   /**
    * Render data to HTML using Soy.
    *
    * @param req in-progress request.
    * @param res in-progress response.
    * @param templateName Soy template name; must be in one of the template files defined in {@link
    *     Renderer}.
    * @param soyData data for Soy.
    * @throws IOException an error occurred during rendering.
    */
   protected void renderHtml(
       HttpServletRequest req, HttpServletResponse res, String templateName, Map<String, ?> soyData)
       throws IOException {
     renderer.render(req, res, templateName, startHtmlResponse(req, res, soyData));
   }

   /**
    * Start a streaming HTML response with header and footer rendered by Soy.
    *
    * <p>A streaming template includes the special template {@code gitiles.streamingPlaceholder} at
    * the point where data is to be streamed. The template before and after this placeholder is
    * rendered using the provided data map.
    *
    * @param req in-progress request.
    * @param res in-progress response.
    * @param templateName Soy template name; must be in one of the template files defined in {@link
    *     Renderer}.
    * @param soyData data for Soy.
    * @return output stream to render to. The portion of the template before the placeholder is
    *     already written and flushed; the portion after is written only on calling {@code close()}.
    * @throws IOException an error occurred during rendering the header.
    */
   protected OutputStream startRenderStreamingHtml(
       HttpServletRequest req, HttpServletResponse res, String templateName, Map<String, ?> soyData)
       throws IOException {
     req.setAttribute(STREAMING_ATTRIBUTE, true);
     return renderer.renderStreaming(res, templateName, startHtmlResponse(req, res, soyData));
   }

   private Map<String, ?> startHtmlResponse(
       HttpServletRequest req, HttpServletResponse res, Map<String, ?> soyData) throws IOException {
     res.setContentType(FormatType.HTML.getMimeType());
     res.setCharacterEncoding(UTF_8.name());
     setCacheHeaders(res);

     Map<String, Object> allData = getData(req);

     // for backwards compatibility, first try to access the old customHeader config var,
     // then read the new customVariant variable.
     GitilesConfig.putVariant(getAccess(req).getConfig(), "customHeader", "customVariant", allData);
     GitilesConfig.putVariant(getAccess(req).getConfig(), "customVariant", "customVariant", allData);
     allData.putAll(soyData);
     GitilesView view = ViewFilter.getView(req);
     if (!allData.containsKey("repositoryName") && view.getRepositoryName() != null) {
       allData.put("repositoryName", view.getRepositoryName());
     }
     if (!allData.containsKey("breadcrumbs")) {
       allData.put("breadcrumbs", view.getBreadcrumbs());
     }

     res.setStatus(HttpServletResponse.SC_OK);
     return allData;
   }

   /**
    * Render data to JSON using GSON.
    *
    * @param req in-progress request.
    * @param res in-progress response.
    * @param src @see com.google.gson.Gson#toJson(Object, Type, Appendable)
    * @param typeOfSrc @see com.google.gson.Gson#toJson(Object, Type, Appendable)
    */
   protected void renderJson(
       HttpServletRequest req, HttpServletResponse res, Object src, Type typeOfSrc)
       throws IOException {
     setApiHeaders(req, res, JSON);
     res.setStatus(SC_OK);
     try (Writer writer = newWriter(req, res)) {
       newGsonBuilder(req).create().toJson(src, typeOfSrc, writer);
       writer.write('\n');
     }
   }

   @SuppressWarnings("unused") // Used in subclasses.
   protected GsonBuilder newGsonBuilder(HttpServletRequest req) throws IOException {
     return new GsonBuilder()
         .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
         .setPrettyPrinting()
         .generateNonExecutableJson();
   }

   /**
    * @see #startRenderText(HttpServletRequest, HttpServletResponse)
    * @param req in-progress request.
    * @param res in-progress response.
    * @param contentType contentType to set.
    * @return the response's writer.
    */
   protected Writer startRenderText(
       HttpServletRequest req, HttpServletResponse res, String contentType) throws IOException {
     setApiHeaders(req, res, contentType);
     return newWriter(req, res);
   }

   /**
    * Prepare the response to render plain text.
    *
    * <p>Unlike {@link #renderHtml(HttpServletRequest, HttpServletResponse, String, Map)} and {@link
    * #renderJson(HttpServletRequest, HttpServletResponse, Object, Type)}, which assume the data to
    * render is already completely prepared, this method does not write any data, only headers, and
    * returns the response's ready-to-use writer.
    *
    * @param req in-progress request.
    * @param res in-progress response.
    * @return the response's writer.
    */
   protected Writer startRenderText(HttpServletRequest req, HttpServletResponse res)
       throws IOException {
     return startRenderText(req, res, TEXT.getMimeType());
   }

   /**
    * Render an error as plain text.
    *
    * @param req in-progress request.
    * @param res in-progress response.
    * @param statusCode HTTP status code.
    * @param message full message text.
    * @throws IOException
    */
   protected void renderTextError(
       HttpServletRequest req, HttpServletResponse res, int statusCode, String message)
       throws IOException {
     res.setStatus(statusCode);
     setApiHeaders(req, res, TEXT);
     setCacheHeaders(res);
     try (Writer out = newWriter(req, res)) {
       out.write(message);
     }
   }

   protected GitilesAccess getAccess(HttpServletRequest req) {
     GitilesAccess access = (GitilesAccess) req.getAttribute(ACCESS_ATTRIBUTE);
     if (access == null) {
       access = accessFactory.forRequest(req);
       req.setAttribute(ACCESS_ATTRIBUTE, access);
     }
     return access;
   }

   protected void setCacheHeaders(HttpServletResponse res) {
     setNotCacheable(res);
   }

   protected void setApiHeaders(
        HttpServletRequest req, HttpServletResponse res, String contentType) throws IOException {
     if (!Strings.isNullOrEmpty(contentType)) {
       res.setContentType(contentType);
     }
     res.setCharacterEncoding(UTF_8.name());
     res.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment");

     GitilesAccess access = getAccess(req);
     String[] allowOrigin = access.getConfig().getStringList("gitiles", null, "allowOriginRegex");

     if (allowOrigin.length > 0) {
       String origin = req.getHeader(HttpHeaders.ORIGIN);
       Pattern allowOriginPattern = Pattern.compile(Joiner.on("|").join(allowOrigin));

       if (!Strings.isNullOrEmpty(origin) && allowOriginPattern.matcher(origin).matches()) {
         res.setHeader(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN, origin);
       }
     } else {
       res.setHeader(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN, "*");
     }
     setCacheHeaders(res);
   }

   protected void setApiHeaders(HttpServletRequest req, HttpServletResponse res, FormatType type)
       throws IOException {
     setApiHeaders(req, res, type.getMimeType());
   }

   protected void setDownloadHeaders(HttpServletResponse res, String filename, String contentType) {
     res.setContentType(contentType);
     res.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + filename);
     setCacheHeaders(res);
   }

   protected static Writer newWriter(OutputStream os, HttpServletResponse res) throws IOException {
     return new OutputStreamWriter(os, res.getCharacterEncoding());
   }

   private Writer newWriter(HttpServletRequest req, HttpServletResponse res) throws IOException {
     OutputStream out;
     if (acceptsGzipEncoding(req)) {
       res.addHeader(HttpHeaders.VARY, HttpHeaders.ACCEPT_ENCODING);
       res.setHeader(HttpHeaders.CONTENT_ENCODING, "gzip");
       out = new GZIPOutputStream(res.getOutputStream());
     } else {
       out = res.getOutputStream();
     }
     return newWriter(out, res);
   }

   protected static boolean acceptsGzipEncoding(HttpServletRequest req) {
     String accepts = req.getHeader(HttpHeaders.ACCEPT_ENCODING);
     if (accepts == null) {
       return false;
     }
     for (int b = 0; b < accepts.length(); ) {
       int comma = accepts.indexOf(',', b);
       int e = 0 <= comma ? comma : accepts.length();
       String term = accepts.substring(b, e).trim();
       if (term.equals(ENCODING_GZIP)) {
         return true;
       }
       b = e + 1;
     }
     return false;
   }

   protected static byte[] gzip(byte[] raw) throws IOException {
     ByteArrayOutputStream out = new ByteArrayOutputStream();
     try (GZIPOutputStream gz = new GZIPOutputStream(out)) {
       gz.write(raw);
     }
     return out.toByteArray();
   }
 }
	// Copyright 2012 Google Inc. All Rights Reserved.
	//
	// 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.

	package com.google.gitiles;

	import static com.google.common.base.MoreObjects.firstNonNull;
	import static com.google.gitiles.FormatType.DEFAULT;
	import static com.google.gitiles.FormatType.HTML;
	import static com.google.gitiles.FormatType.JSON;
	import static com.google.gitiles.FormatType.TEXT;
	import static java.nio.charset.StandardCharsets.UTF_8;
	import static javax.servlet.http.HttpServletResponse.SC_BAD_REQUEST;
	import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
	import static javax.servlet.http.HttpServletResponse.SC_OK;
	import static org.eclipse.jgit.util.HttpSupport.ENCODING_GZIP;

	import com.google.common.base.Joiner;
	import com.google.common.base.Optional;
	import com.google.common.base.Strings;
	import com.google.common.collect.ImmutableMap;
	import com.google.common.collect.Maps;
	import com.google.common.net.HttpHeaders;
	import com.google.gson.FieldNamingPolicy;
	import com.google.gson.GsonBuilder;
	import java.io.ByteArrayOutputStream;
	import java.io.IOException;
	import java.io.OutputStream;
	import java.io.OutputStreamWriter;
	import java.io.Writer;
	import java.lang.reflect.Type;
	import java.util.Map;
	import java.util.List;
	import java.util.regex.Pattern;
	import java.util.zip.GZIPOutputStream;
	import javax.servlet.ServletException;
	import javax.servlet.http.HttpServlet;
	import javax.servlet.http.HttpServletRequest;
	import javax.servlet.http.HttpServletResponse;
	import org.joda.time.Instant;

	/** Base servlet class for Gitiles servlets that serve Soy templates. */
	public abstract class BaseServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private static final String ACCESS_ATTRIBUTE = BaseServlet.class.getName() + "/GitilesAccess";
	private static final String DATA_ATTRIBUTE = BaseServlet.class.getName() + "/Data";
	private static final String STREAMING_ATTRIBUTE = BaseServlet.class.getName() + "/Streaming";

	static void setNotCacheable(HttpServletResponse res) {
	res.setHeader(HttpHeaders.CACHE_CONTROL, "no-cache, no-store, max-age=0, must-revalidate");
	res.setHeader(HttpHeaders.PRAGMA, "no-cache");
	res.setHeader(HttpHeaders.EXPIRES, "Mon, 01 Jan 1990 00:00:00 GMT");
	res.setDateHeader(HttpHeaders.DATE, new Instant().getMillis());
	}

	public static BaseServlet notFoundServlet() {
	return new BaseServlet(null, null) {
	private static final long serialVersionUID = 1L;

	@Override
	public void service(HttpServletRequest req, HttpServletResponse res) {
	res.setStatus(SC_NOT_FOUND);
	}
	};
	}

	public static Map<String, String> menuEntry(String text, String url) {
	if (url != null) {
	return ImmutableMap.of("text", text, "url", url);
	}
	return ImmutableMap.of("text", text);
	}

	public static boolean isStreamingResponse(HttpServletRequest req) {
	return firstNonNull((Boolean) req.getAttribute(STREAMING_ATTRIBUTE), false);
	}

	protected static ArchiveFormat getArchiveFormat(GitilesAccess access) throws IOException {
	return ArchiveFormat.getDefault(access.getConfig());
	}

	/**
	* Put a value into a request's Soy data map.
	*
	* @param req in-progress request.
	* @param key key.
	* @param value Soy data value.
	*/
	public static void putSoyData(HttpServletRequest req, String key, Object value) {
	getData(req).put(key, value);
	}

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse res)
	throws IOException, ServletException {
	Optional<FormatType> format = getFormat(req);
	if (!format.isPresent()) {
	res.sendError(SC_BAD_REQUEST);
	return;
	}
	switch (format.get()) {
	case HTML:
	doGetHtml(req, res);
	break;
	case TEXT:
	doGetText(req, res);
	break;
	case JSON:
	doGetJson(req, res);
	break;
	case DEFAULT:
	default:
	res.sendError(SC_BAD_REQUEST);
	break;
	}
	}

	protected Optional<FormatType> getFormat(HttpServletRequest req) {
	Optional<FormatType> format = FormatType.getFormatType(req);
	if (format.isPresent() && format.get() == DEFAULT) {
	return Optional.of(getDefaultFormat(req));
	}
	return format;
	}

	/**
	* @param req in-progress request.
	* @return the default {@link FormatType} used when {@code ?format=} is not specified.
	*/
	protected FormatType getDefaultFormat(HttpServletRequest req) {
	return HTML;
	}

	/**
	* Handle a GET request when the requested format type was HTML.
	*
	* @param req in-progress request.
	* @param res in-progress response.
	*/
	protected void doGetHtml(HttpServletRequest req, HttpServletResponse res) throws IOException {
	res.sendError(SC_BAD_REQUEST);
	}

	/**
	* Handle a GET request when the requested format type was plain text.
	*
	* @param req in-progress request.
	* @param res in-progress response.
	*/
	protected void doGetText(HttpServletRequest req, HttpServletResponse res) throws IOException {
	res.sendError(SC_BAD_REQUEST);
	}

	/**
	* Handle a GET request when the requested format type was JSON.
	*
	* @param req in-progress request.
	* @param res in-progress response.
	*/
	protected void doGetJson(HttpServletRequest req, HttpServletResponse res) throws IOException {
	res.sendError(SC_BAD_REQUEST);
	}

	protected static Map<String, Object> getData(HttpServletRequest req) {
	@SuppressWarnings("unchecked")
	Map<String, Object> data = (Map<String, Object>) req.getAttribute(DATA_ATTRIBUTE);
	if (data == null) {
	data = Maps.newHashMap();
	req.setAttribute(DATA_ATTRIBUTE, data);
	}
	return data;
	}

	protected final Renderer renderer;
	private final GitilesAccess.Factory accessFactory;

	protected BaseServlet(Renderer renderer, GitilesAccess.Factory accessFactory) {
	this.renderer = renderer;
	this.accessFactory = accessFactory;
	}

	/**
	* Render data to HTML using Soy.
	*
	* @param req in-progress request.
	* @param res in-progress response.
	* @param templateName Soy template name; must be in one of the template files defined in {@link
	* Renderer}.
	* @param soyData data for Soy.
	* @throws IOException an error occurred during rendering.
	*/
	protected void renderHtml(
	HttpServletRequest req, HttpServletResponse res, String templateName, Map<String, ?> soyData)
	throws IOException {
	renderer.render(req, res, templateName, startHtmlResponse(req, res, soyData));
	}

	/**
	* Start a streaming HTML response with header and footer rendered by Soy.
	*
	* <p>A streaming template includes the special template {@code gitiles.streamingPlaceholder} at
	* the point where data is to be streamed. The template before and after this placeholder is
	* rendered using the provided data map.
	*
	* @param req in-progress request.
	* @param res in-progress response.
	* @param templateName Soy template name; must be in one of the template files defined in {@link
	* Renderer}.
	* @param soyData data for Soy.
	* @return output stream to render to. The portion of the template before the placeholder is
	* already written and flushed; the portion after is written only on calling {@code close()}.
	* @throws IOException an error occurred during rendering the header.
	*/
	protected OutputStream startRenderStreamingHtml(
	HttpServletRequest req, HttpServletResponse res, String templateName, Map<String, ?> soyData)
	throws IOException {
	req.setAttribute(STREAMING_ATTRIBUTE, true);
	return renderer.renderStreaming(res, templateName, startHtmlResponse(req, res, soyData));
	}

	private Map<String, ?> startHtmlResponse(
	HttpServletRequest req, HttpServletResponse res, Map<String, ?> soyData) throws IOException {
	res.setContentType(FormatType.HTML.getMimeType());
	res.setCharacterEncoding(UTF_8.name());
	setCacheHeaders(res);

	Map<String, Object> allData = getData(req);

	// for backwards compatibility, first try to access the old customHeader config var,
	// then read the new customVariant variable.
	GitilesConfig.putVariant(getAccess(req).getConfig(), "customHeader", "customVariant", allData);
	GitilesConfig.putVariant(getAccess(req).getConfig(), "customVariant", "customVariant", allData);
	allData.putAll(soyData);
	GitilesView view = ViewFilter.getView(req);
	if (!allData.containsKey("repositoryName") && view.getRepositoryName() != null) {
	allData.put("repositoryName", view.getRepositoryName());
	}
	if (!allData.containsKey("breadcrumbs")) {
	allData.put("breadcrumbs", view.getBreadcrumbs());
	}

	res.setStatus(HttpServletResponse.SC_OK);
	return allData;
	}

	/**
	* Render data to JSON using GSON.
	*
	* @param req in-progress request.
	* @param res in-progress response.
	* @param src @see com.google.gson.Gson#toJson(Object, Type, Appendable)
	* @param typeOfSrc @see com.google.gson.Gson#toJson(Object, Type, Appendable)
	*/
	protected void renderJson(
	HttpServletRequest req, HttpServletResponse res, Object src, Type typeOfSrc)
	throws IOException {
	setApiHeaders(req, res, JSON);
	res.setStatus(SC_OK);
	try (Writer writer = newWriter(req, res)) {
	newGsonBuilder(req).create().toJson(src, typeOfSrc, writer);
	writer.write('\n');
	}
	}

	@SuppressWarnings("unused") // Used in subclasses.
	protected GsonBuilder newGsonBuilder(HttpServletRequest req) throws IOException {
	return new GsonBuilder()
	.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
	.setPrettyPrinting()
	.generateNonExecutableJson();
	}

	/**
	* @see #startRenderText(HttpServletRequest, HttpServletResponse)
	* @param req in-progress request.
	* @param res in-progress response.
	* @param contentType contentType to set.
	* @return the response's writer.
	*/
	protected Writer startRenderText(
	HttpServletRequest req, HttpServletResponse res, String contentType) throws IOException {
	setApiHeaders(req, res, contentType);
	return newWriter(req, res);
	}

	/**
	* Prepare the response to render plain text.
	*
	* <p>Unlike {@link #renderHtml(HttpServletRequest, HttpServletResponse, String, Map)} and {@link
	* #renderJson(HttpServletRequest, HttpServletResponse, Object, Type)}, which assume the data to
	* render is already completely prepared, this method does not write any data, only headers, and
	* returns the response's ready-to-use writer.
	*
	* @param req in-progress request.
	* @param res in-progress response.
	* @return the response's writer.
	*/
	protected Writer startRenderText(HttpServletRequest req, HttpServletResponse res)
	throws IOException {
	return startRenderText(req, res, TEXT.getMimeType());
	}

	/**
	* Render an error as plain text.
	*
	* @param req in-progress request.
	* @param res in-progress response.
	* @param statusCode HTTP status code.
	* @param message full message text.
	* @throws IOException
	*/
	protected void renderTextError(
	HttpServletRequest req, HttpServletResponse res, int statusCode, String message)
	throws IOException {
	res.setStatus(statusCode);
	setApiHeaders(req, res, TEXT);
	setCacheHeaders(res);
	try (Writer out = newWriter(req, res)) {
	out.write(message);
	}
	}

	protected GitilesAccess getAccess(HttpServletRequest req) {
	GitilesAccess access = (GitilesAccess) req.getAttribute(ACCESS_ATTRIBUTE);
	if (access == null) {
	access = accessFactory.forRequest(req);
	req.setAttribute(ACCESS_ATTRIBUTE, access);
	}
	return access;
	}

	protected void setCacheHeaders(HttpServletResponse res) {
	setNotCacheable(res);
	}

	protected void setApiHeaders(
	HttpServletRequest req, HttpServletResponse res, String contentType) throws IOException {
	if (!Strings.isNullOrEmpty(contentType)) {
	res.setContentType(contentType);
	}
	res.setCharacterEncoding(UTF_8.name());
	res.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment");

	GitilesAccess access = getAccess(req);
	String[] allowOrigin = access.getConfig().getStringList("gitiles", null, "allowOriginRegex");

	if (allowOrigin.length > 0) {
	String origin = req.getHeader(HttpHeaders.ORIGIN);
	Pattern allowOriginPattern = Pattern.compile(Joiner.on("\|").join(allowOrigin));

	if (!Strings.isNullOrEmpty(origin) && allowOriginPattern.matcher(origin).matches()) {
	res.setHeader(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN, origin);
	}
	} else {
	res.setHeader(HttpHeaders.ACCESS_CONTROL_ALLOW_ORIGIN, "*");
	}
	setCacheHeaders(res);
	}

	protected void setApiHeaders(HttpServletRequest req, HttpServletResponse res, FormatType type)
	throws IOException {
	setApiHeaders(req, res, type.getMimeType());
	}

	protected void setDownloadHeaders(HttpServletResponse res, String filename, String contentType) {
	res.setContentType(contentType);
	res.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + filename);
	setCacheHeaders(res);
	}

	protected static Writer newWriter(OutputStream os, HttpServletResponse res) throws IOException {
	return new OutputStreamWriter(os, res.getCharacterEncoding());
	}

	private Writer newWriter(HttpServletRequest req, HttpServletResponse res) throws IOException {
	OutputStream out;
	if (acceptsGzipEncoding(req)) {
	res.addHeader(HttpHeaders.VARY, HttpHeaders.ACCEPT_ENCODING);
	res.setHeader(HttpHeaders.CONTENT_ENCODING, "gzip");
	out = new GZIPOutputStream(res.getOutputStream());
	} else {
	out = res.getOutputStream();
	}
	return newWriter(out, res);
	}

	protected static boolean acceptsGzipEncoding(HttpServletRequest req) {
	String accepts = req.getHeader(HttpHeaders.ACCEPT_ENCODING);
	if (accepts == null) {
	return false;
	}
	for (int b = 0; b < accepts.length(); ) {
	int comma = accepts.indexOf(',', b);
	int e = 0 <= comma ? comma : accepts.length();
	String term = accepts.substring(b, e).trim();
	if (term.equals(ENCODING_GZIP)) {
	return true;
	}
	b = e + 1;
	}
	return false;
	}

	protected static byte[] gzip(byte[] raw) throws IOException {
	ByteArrayOutputStream out = new ByteArrayOutputStream();
	try (GZIPOutputStream gz = new GZIPOutputStream(out)) {
	gz.write(raw);
	}
	return out.toByteArray();
	}
	}