diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/BaseServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/BaseServlet.java
index c92579d..a2bc65c 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/BaseServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/BaseServlet.java
@@ -14,18 +14,30 @@
 
 package com.google.gitiles;
 
+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 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 com.google.common.base.Charsets;
 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 org.joda.time.Instant;
 
 import java.io.IOException;
+import java.io.PrintWriter;
+import java.lang.reflect.Type;
 import java.util.Map;
 
+import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -60,6 +72,77 @@
     }
   }
 
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse res)
+      throws IOException, ServletException {
+    FormatType format;
+    try {
+      format = FormatType.getFormatType(req);
+    } catch (IllegalArgumentException err) {
+      res.sendError(SC_BAD_REQUEST);
+      return;
+    }
+    if (format == DEFAULT) {
+      format = getDefaultFormat(req);
+    }
+    switch (format) {
+      case HTML:
+        doGetHtml(req, res);
+        break;
+      case TEXT:
+        doGetText(req, res);
+        break;
+      case JSON:
+        doGetJson(req, res);
+        break;
+      default:
+        res.sendError(SC_BAD_REQUEST);
+        break;
+    }
+  }
+
+  /**
+   * @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, ServletException {
+    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, ServletException {
+    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, ServletException {
+    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);
@@ -91,7 +174,16 @@
     getData(req).put(key, value);
   }
 
-  protected void render(HttpServletRequest req, HttpServletResponse res, String templateName,
+  /**
+   * Render data to HTML using Soy.
+   *
+   * @param req in-progress request.
+   * @param res in-progress response.
+   * @param key key.
+   * @param templateName Soy template name; must be in one of the template files
+   *     defined in {@link Renderer#SOY_FILENAMES}.
+   */
+  protected void renderHtml(HttpServletRequest req, HttpServletResponse res, String templateName,
       Map<String, ?> soyData) throws IOException {
     try {
       res.setContentType(FormatType.HTML.getMimeType());
@@ -115,6 +207,57 @@
     }
   }
 
+  /**
+   * Render data to JSON using GSON.
+   *
+   * @param req in-progress request.
+   * @param res in-progress response.
+   * @param src @see Gson#toJson(Object, Type, Appendable)
+   * @param typeOfSrc @see Gson#toJson(Object, Type, Appendable)
+   */
+  protected void renderJson(HttpServletRequest req, HttpServletResponse res, Object src,
+      Type typeOfSrc) throws IOException {
+    res.setContentType(JSON.getMimeType());
+    res.setCharacterEncoding("UTF-8");
+    res.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment");
+    setCacheHeaders(req, res);
+    res.setStatus(SC_OK);
+
+    PrintWriter writer = res.getWriter();
+    new GsonBuilder()
+      .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
+      .setPrettyPrinting()
+      .generateNonExecutableJson()
+      .create()
+      .toJson(src, typeOfSrc, writer);
+    writer.print('\n');
+    writer.close();
+  }
+
+  /**
+   * 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 PrintWriter startRenderText(HttpServletRequest req, HttpServletResponse res)
+      throws IOException {
+    res.setContentType(TEXT.getMimeType());
+    res.setCharacterEncoding("UTF-8");
+    res.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment");
+    setCacheHeaders(req, res);
+    return res.getWriter();
+  }
+
   protected void setCacheHeaders(HttpServletRequest req, HttpServletResponse res) {
     setNotCacheable(res);
   }
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/HostIndexServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/HostIndexServlet.java
index 598527c..a046ff1 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/HostIndexServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/HostIndexServlet.java
@@ -15,9 +15,7 @@
 package com.google.gitiles;
 
 import static com.google.common.base.Preconditions.checkNotNull;
-import static com.google.gitiles.FormatType.JSON;
-import static com.google.gitiles.FormatType.TEXT;
-import static javax.servlet.http.HttpServletResponse.SC_BAD_REQUEST;
+
 import static javax.servlet.http.HttpServletResponse.SC_FORBIDDEN;
 import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
 import static javax.servlet.http.HttpServletResponse.SC_SERVICE_UNAVAILABLE;
@@ -26,9 +24,6 @@
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Sets;
-import com.google.common.net.HttpHeaders;
-import com.google.gson.FieldNamingPolicy;
-import com.google.gson.GsonBuilder;
 import com.google.gson.reflect.TypeToken;
 import com.google.template.soy.data.SoyListData;
 import com.google.template.soy.data.SoyMapData;
@@ -64,55 +59,36 @@
     this.accessFactory = checkNotNull(accessFactory, "accessFactory");
   }
 
-  @Override
-  protected void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException {
-    FormatType format;
-    try {
-      format = FormatType.getFormatType(req);
-    } catch (IllegalArgumentException err) {
-      res.sendError(SC_BAD_REQUEST);
-      return;
-    }
+  private Map<String, RepositoryDescription> getDescriptions(HttpServletRequest req,
+      HttpServletResponse res) throws IOException {
+    return getDescriptions(req, res, parseShowBranch(req));
+  }
 
-    Set<String> branches = parseShowBranch(req);
+  private Map<String, RepositoryDescription> getDescriptions(HttpServletRequest req,
+      HttpServletResponse res, Set<String> branches) throws IOException {
     Map<String, RepositoryDescription> descs;
     try {
       descs = accessFactory.forRequest(req).listRepositories(branches);
     } catch (RepositoryNotFoundException e) {
       res.sendError(SC_NOT_FOUND);
-      return;
+      return null;
     } catch (ServiceNotEnabledException e) {
       res.sendError(SC_FORBIDDEN);
-      return;
+      return null;
     } catch (ServiceNotAuthorizedException e) {
       res.sendError(SC_UNAUTHORIZED);
-      return;
+      return null;
     } catch (ServiceMayNotContinueException e) {
       // TODO(dborowitz): Show the error message to the user.
       res.sendError(SC_FORBIDDEN);
-      return;
+      return null;
     } catch (IOException err) {
       String name = urls.getHostName(req);
       log.warn("Cannot scan repositories" + (name != null ? "for " + name : ""), err);
       res.sendError(SC_SERVICE_UNAVAILABLE);
-      return;
+      return null;
     }
-
-    switch (format) {
-      case HTML:
-      case DEFAULT:
-      default:
-        displayHtml(req, res, descs);
-        break;
-
-      case TEXT:
-        displayText(req, res, branches, descs);
-        break;
-
-      case JSON:
-        displayJson(req, res, descs);
-        break;
-    }
+    return descs;
   }
 
   private SoyMapData toSoyMapData(RepositoryDescription desc, GitilesView view) {
@@ -125,27 +101,32 @@
             .toUrl());
   }
 
-  private void displayHtml(HttpServletRequest req, HttpServletResponse res,
-      Map<String, RepositoryDescription> descs) throws IOException {
+  @Override
+  protected void doGetHtml(HttpServletRequest req, HttpServletResponse res) throws IOException {
+    Map<String, RepositoryDescription> descs = getDescriptions(req, res);
+    if (descs == null) {
+      return;
+    }
     SoyListData repos = new SoyListData();
     for (RepositoryDescription desc : descs.values()) {
       repos.add(toSoyMapData(desc, ViewFilter.getView(req)));
     }
 
-    render(req, res, "gitiles.hostIndex", ImmutableMap.of(
+    renderHtml(req, res, "gitiles.hostIndex", ImmutableMap.of(
         "hostName", urls.getHostName(req),
         "baseUrl", urls.getBaseGitUrl(req),
         "repositories", repos));
   }
 
-  private void displayText(HttpServletRequest req, HttpServletResponse res,
-      Set<String> branches, Map<String, RepositoryDescription> descs) throws IOException {
-    res.setContentType(TEXT.getMimeType());
-    res.setCharacterEncoding("UTF-8");
-    res.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment");
-    setNotCacheable(res);
+  @Override
+  protected void doGetText(HttpServletRequest req, HttpServletResponse res) throws IOException {
+    Set<String> branches = parseShowBranch(req);
+    Map<String, RepositoryDescription> descs = getDescriptions(req, res, branches);
+    if (descs == null) {
+      return;
+    }
 
-    PrintWriter writer = res.getWriter();
+    PrintWriter writer = startRenderText(req, res);
     for (RepositoryDescription repo : descs.values()) {
       for (String name : branches) {
         String ref = repo.branches.get(name);
@@ -163,24 +144,13 @@
     writer.close();
   }
 
-  private void displayJson(HttpServletRequest req, HttpServletResponse res,
-      Map<String, RepositoryDescription> descs) throws IOException {
-    res.setContentType(JSON.getMimeType());
-    res.setCharacterEncoding("UTF-8");
-    res.setHeader(HttpHeaders.CONTENT_DISPOSITION, "attachment");
-    setNotCacheable(res);
-
-    PrintWriter writer = res.getWriter();
-    new GsonBuilder()
-        .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
-        .setPrettyPrinting()
-        .generateNonExecutableJson()
-        .create()
-        .toJson(descs,
-          new TypeToken<Map<String, RepositoryDescription>>() {}.getType(),
-          writer);
-    writer.print('\n');
-    writer.close();
+  @Override
+  protected void doGetJson(HttpServletRequest req, HttpServletResponse res) throws IOException {
+    Map<String, RepositoryDescription> descs = getDescriptions(req, res);
+    if (descs == null) {
+      return;
+    }
+    renderJson(req, res, descs, new TypeToken<Map<String, RepositoryDescription>>() {}.getType());
   }
 
   private static Set<String> parseShowBranch(HttpServletRequest req) {
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/LogServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/LogServlet.java
index 748c5c9..46b6c44 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/LogServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/LogServlet.java
@@ -119,7 +119,7 @@
 
       data.put("title", title);
 
-      render(req, res, "gitiles.logDetail", data);
+      renderHtml(req, res, "gitiles.logDetail", data);
     } catch (RevWalkException e) {
       log.warn("Error in rev walk", e);
       res.setStatus(SC_INTERNAL_SERVER_ERROR);
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/PathServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/PathServlet.java
index 387e342..fff423a 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/PathServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/PathServlet.java
@@ -284,7 +284,7 @@
       }
     }
     // TODO(sop): Allow caching trees by SHA-1 when no S cookie is sent.
-    render(req, res, "gitiles.pathDetail", ImmutableMap.of(
+    renderHtml(req, res, "gitiles.pathDetail", ImmutableMap.of(
         "title", !view.getTreePath().isEmpty() ? view.getTreePath() : "/",
         "breadcrumbs", view.getBreadcrumbs(hasSingleTree),
         "type", FileType.TREE.toString(),
@@ -305,7 +305,7 @@
       List<Boolean> hasSingleTree) throws IOException {
     GitilesView view = ViewFilter.getView(req);
     // TODO(sop): Allow caching files by SHA-1 when no S cookie is sent.
-    render(req, res, "gitiles.pathDetail", ImmutableMap.of(
+    renderHtml(req, res, "gitiles.pathDetail", ImmutableMap.of(
         "title", ViewFilter.getView(req).getTreePath(),
         "breadcrumbs", view.getBreadcrumbs(hasSingleTree),
         "type", FileType.forEntry(tw).toString(),
@@ -328,7 +328,7 @@
       data.put("sha", ObjectId.toString(id));
       data.put("data", null);
       data.put("size", Long.toString(loader.getSize()));
-      render(req, res, "gitiles.pathDetail", ImmutableMap.of(
+      renderHtml(req, res, "gitiles.pathDetail", ImmutableMap.of(
           "title", ViewFilter.getView(req).getTreePath(),
           "breadcrumbs", view.getBreadcrumbs(hasSingleTree),
           "type", FileType.REGULAR_FILE.toString(),
@@ -349,7 +349,7 @@
     }
 
     // TODO(sop): Allow caching files by SHA-1 when no S cookie is sent.
-    render(req, res, "gitiles.pathDetail", ImmutableMap.of(
+    renderHtml(req, res, "gitiles.pathDetail", ImmutableMap.of(
         "title", ViewFilter.getView(req).getTreePath(),
         "breadcrumbs", view.getBreadcrumbs(hasSingleTree),
         "type", FileType.SYMLINK.toString(),
@@ -396,7 +396,7 @@
       }
 
       // TODO(sop): Allow caching links by SHA-1 when no S cookie is sent.
-      render(req, res, "gitiles.pathDetail", ImmutableMap.of(
+      renderHtml(req, res, "gitiles.pathDetail", ImmutableMap.of(
           "title", view.getTreePath(),
           "type", FileType.GITLINK.toString(),
           "data", data));
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/RefServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/RefServlet.java
index 959a449..bb51f04 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/RefServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/RefServlet.java
@@ -60,7 +60,7 @@
     } finally {
       walk.release();
     }
-    render(req, res, "gitiles.refsDetail",
+    renderHtml(req, res, "gitiles.refsDetail",
         ImmutableMap.of("branches", getBranches(req, 0), "tags", tags));
   }
 
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/RepositoryIndexServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/RepositoryIndexServlet.java
index eb61a25..9672815 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/RepositoryIndexServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/RepositoryIndexServlet.java
@@ -55,7 +55,7 @@
 
   @Override
   protected void doGet(HttpServletRequest req, HttpServletResponse res) throws IOException {
-    render(req, res, "gitiles.repositoryIndex", buildData(req));
+    renderHtml(req, res, "gitiles.repositoryIndex", buildData(req));
   }
 
   @VisibleForTesting
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/RevisionServlet.java b/gitiles-servlet/src/main/java/com/google/gitiles/RevisionServlet.java
index c2eacdf..e4258c0 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/RevisionServlet.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/RevisionServlet.java
@@ -110,7 +110,7 @@
         }
       }
 
-      render(req, res, "gitiles.revisionDetail", ImmutableMap.of(
+      renderHtml(req, res, "gitiles.revisionDetail", ImmutableMap.of(
           "title", view.getRevision().getName(),
           "objects", soyObjects,
           "hasBlob", hasBlob));