Simplify RestModifyView interface

The inputType can be determined by looking at the declaration
of the interface. We don't need to implement a method in each
view implementation to supply the correct data for reflection
in RestApiServlet.

Change-Id: I1afae6ddef661722efe39ccc917c028e7e993595

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/RestModifyView.java

@@ -25,13 +25,6 @@ package com.google.gerrit.extensions.restapi;
  * @param <I> type of input the JSON parser will parse the input into.
  */
 public interface RestModifyView<R extends RestResource, I> extends RestView<R> {
-  /**
-   * @return Java class object defining the input type. The JSON parser will
-   *         parse the supplied request body into a new instance of this class
-   *         before passing it to apply.
-   */
-  Class<I> inputType();
-
   /**
    * Process the view operation by altering the resource.
    *

gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java

@@ -93,6 +93,8 @@ import java.io.Writer;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
@@ -264,7 +266,7 @@ public class RestApiServlet extends HttpServlet {
         RestModifyView<RestResource, Object> m =
             (RestModifyView<RestResource, Object>) view;
 
-        result = m.apply(rsrc, parseRequest(req, m.inputType()));
+        result = m.apply(rsrc, parseRequest(req, inputType(m)));
       } else if (view instanceof RestReadView<?>) {
         result = ((RestReadView<RestResource>) view).apply(rsrc);
       } else {
@@ -308,7 +310,43 @@ public class RestApiServlet extends HttpServlet {
     }
   }
 
-  private Object parseRequest(HttpServletRequest req, Class<Object> type)
+  private static Type inputType(RestModifyView<RestResource, Object> m) {
+    Type inputType = extractInputType(m.getClass());
+    if (inputType == null) {
+      throw new IllegalStateException(String.format(
+          "View %s does not correctly implement %s",
+          m.getClass(), RestModifyView.class.getSimpleName()));
+    }
+    return inputType;
+  }
+
+  @SuppressWarnings("rawtypes")
+  private static Type extractInputType(Class clazz) {
+    for (Type t : clazz.getGenericInterfaces()) {
+      if (t instanceof ParameterizedType
+          && ((ParameterizedType) t).getRawType() == RestModifyView.class) {
+        return ((ParameterizedType) t).getActualTypeArguments()[1];
+      }
+    }
+
+    if (clazz.getSuperclass() != null) {
+      Type i = extractInputType(clazz.getSuperclass());
+      if (i != null) {
+        return i;
+      }
+    }
+
+    for (Class t : clazz.getInterfaces()) {
+      Type i = extractInputType(t);
+      if (i != null) {
+        return i;
+      }
+    }
+
+    return null;
+  }
+
+  private Object parseRequest(HttpServletRequest req, Type type)
       throws IOException, BadRequestException, SecurityException,
       IllegalArgumentException, NoSuchMethodException, IllegalAccessException,
       InstantiationException, InvocationTargetException, MethodNotAllowedException {
@@ -333,7 +371,7 @@ public class RestApiServlet extends HttpServlet {
       return parsePutInput(req, type);
     } else if ("DELETE".equals(req.getMethod()) && hasNoBody(req)) {
       return null;
-    } else if (type.getDeclaredFields().length == 0 && hasNoBody(req)) {
+    } else if (isEmptyType(type) && hasNoBody(req)) {
       return createInstance(type);
     } else if (isType("text/plain", req.getContentType())) {
       BufferedReader br = req.getReader();
@@ -358,6 +396,19 @@ public class RestApiServlet extends HttpServlet {
     }
   }
 
+  @SuppressWarnings("rawtypes")
+  private static boolean isEmptyType(Type type) {
+    if (type == String.class) {
+      return false;
+    } else if (type instanceof Class) {
+      Class clazz = (Class) type;
+      Class base = clazz.getSuperclass();
+      return clazz.getDeclaredFields().length == 0
+          && (base == null || isEmptyType(base));
+    }
+    return false;
+  }
+
   private static boolean hasNoBody(HttpServletRequest req) {
     int len = req.getContentLength();
     String type = req.getContentType();
@@ -365,21 +416,24 @@ public class RestApiServlet extends HttpServlet {
         || (len == 0 && isType(FORM_TYPE, type));
   }
 
-  private static boolean acceptsPutInput(Class<Object> type) {
+  @SuppressWarnings("rawtypes")
-    for (Field f : type.getDeclaredFields()) {
+  private static boolean acceptsPutInput(Type type) {
-      if (f.getType() == PutInput.class) {
+    if (type instanceof Class) {
-        return true;
+      for (Field f : ((Class) type).getDeclaredFields()) {
+        if (f.getType() == PutInput.class) {
+          return true;
+        }
       }
     }
     return false;
   }
 
-  private Object parsePutInput(final HttpServletRequest req, Class<Object> type)
+  private Object parsePutInput(final HttpServletRequest req, Type type)
       throws SecurityException, NoSuchMethodException,
       IllegalArgumentException, InstantiationException, IllegalAccessException,
       InvocationTargetException, MethodNotAllowedException {
     Object obj = createInstance(type);
-    for (Field f : type.getDeclaredFields()) {
+    for (Field f : obj.getClass().getDeclaredFields()) {
       if (f.getType() == PutInput.class) {
         f.setAccessible(true);
         f.set(obj, new PutInput() {
@@ -404,12 +458,16 @@ public class RestApiServlet extends HttpServlet {
     throw new MethodNotAllowedException();
   }
 
-  private Object parseString(String value, Class<Object> type)
+  private Object parseString(String value, Type type)
       throws BadRequestException, SecurityException, NoSuchMethodException,
       IllegalArgumentException, IllegalAccessException, InstantiationException,
       InvocationTargetException {
+    if (type == String.class) {
+      return value;
+    }
+
     Object obj = createInstance(type);
-    Field[] fields = type.getDeclaredFields();
+    Field[] fields = obj.getClass().getDeclaredFields();
     if (fields.length == 0 && Strings.isNullOrEmpty(value)) {
       return obj;
     }
@@ -424,12 +482,17 @@ public class RestApiServlet extends HttpServlet {
     throw new BadRequestException("Expected JSON object");
   }
 
-  private static Object createInstance(Class<Object> type)
+  private static Object createInstance(Type type)
       throws NoSuchMethodException, InstantiationException,
       IllegalAccessException, InvocationTargetException {
-    Constructor<Object> c = type.getDeclaredConstructor();
+    if (type instanceof Class) {
-    c.setAccessible(true);
+      @SuppressWarnings("unchecked")
-    return c.newInstance();
+      Class<Object> clazz = (Class<Object>) type;
+      Constructor<Object> c = clazz.getDeclaredConstructor();
+      c.setAccessible(true);
+      return c.newInstance();
+    }
+    throw new InstantiationException("Cannot make " + type);
   }
 
   private static void replyJson(@Nullable HttpServletRequest req,

gerrit-server/src/main/java/com/google/gerrit/server/change/Abandon.java

@@ -65,11 +65,6 @@ public class Abandon implements RestModifyView<ChangeResource, Input> {
     this.json = json;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(ChangeResource req, Input input)
       throws BadRequestException, AuthException,

gerrit-server/src/main/java/com/google/gerrit/server/change/CreateDraft.java

@@ -41,11 +41,6 @@ class CreateDraft implements RestModifyView<RevisionResource, Input> {
     this.db = db;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Response<GetDraft.Comment> apply(RevisionResource rsrc, Input in)
       throws AuthException, BadRequestException, ResourceConflictException, OrmException {

gerrit-server/src/main/java/com/google/gerrit/server/change/DeleteDraft.java

@@ -35,11 +35,6 @@ class DeleteDraft implements RestModifyView<DraftResource, Input> {
     this.db = db;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(DraftResource rsrc, Input input) throws OrmException {
     db.get().patchComments().delete(Collections.singleton(rsrc.getComment()));

gerrit-server/src/main/java/com/google/gerrit/server/change/DeleteReviewer.java

@@ -43,11 +43,6 @@ class DeleteReviewer implements RestModifyView<ReviewerResource, Input> {
     this.dbProvider = dbProvider;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(ReviewerResource rsrc, Input input)
       throws AuthException, ResourceNotFoundException, OrmException {

gerrit-server/src/main/java/com/google/gerrit/server/change/PostReview.java

@@ -125,11 +125,6 @@ public class PostReview implements RestModifyView<RevisionResource, Input> {
     this.hooks = hooks;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(RevisionResource revision, Input input)
       throws AuthException, BadRequestException, OrmException {

gerrit-server/src/main/java/com/google/gerrit/server/change/PutDraft.java

@@ -55,11 +55,6 @@ class PutDraft implements RestModifyView<DraftResource, Input> {
     this.delete = delete;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(DraftResource rsrc, Input in) throws AuthException,
       BadRequestException, ResourceConflictException, OrmException {

gerrit-server/src/main/java/com/google/gerrit/server/change/PutTopic.java

@@ -48,11 +48,6 @@ class PutTopic implements RestModifyView<ChangeResource, Input> {
     this.dbProvider = dbProvider;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(ChangeResource req, Input input)
       throws BadRequestException, AuthException,

gerrit-server/src/main/java/com/google/gerrit/server/change/Restore.java

@@ -65,11 +65,6 @@ public class Restore implements RestModifyView<ChangeResource, Input> {
     this.json = json;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(ChangeResource req, Input input)
       throws Exception {

gerrit-server/src/main/java/com/google/gerrit/server/change/Revert.java

@@ -83,11 +83,6 @@ public class Revert implements RestModifyView<ChangeResource, Input> {
     this.canonicalWebUrl = canonicalWebUrl;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(ChangeResource req, Input input) throws Exception {
     ChangeControl control = req.getControl();

gerrit-server/src/main/java/com/google/gerrit/server/change/Submit.java

@@ -82,11 +82,6 @@ public class Submit implements RestModifyView<RevisionResource, Input> {
     this.mergeQueue = mergeQueue;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Output apply(RevisionResource rsrc, Input input) throws AuthException,
       ResourceConflictException, RepositoryNotFoundException, IOException,
@@ -305,11 +300,6 @@ public class Submit implements RestModifyView<RevisionResource, Input> {
       this.json = json;
     }
 
-    @Override
-    public Class<Input> inputType() {
-      return Input.class;
-    }
-
     @Override
     public Object apply(ChangeResource rsrc, Input input) throws AuthException,
         ResourceConflictException, RepositoryNotFoundException, IOException,

gerrit-server/src/main/java/com/google/gerrit/server/group/AddMembers.java

@@ -95,11 +95,6 @@ class AddMembers implements RestModifyView<GroupResource, Input> {
     this.self = self;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public List<MemberInfo> apply(GroupResource resource, Input input)
       throws AuthException, MethodNotAllowedException, BadRequestException,
@@ -201,11 +196,6 @@ class AddMembers implements RestModifyView<GroupResource, Input> {
       this.id = id;
     }
 
-    @Override
-    public Class<PutMember.Input> inputType() {
-      return PutMember.Input.class;
-    }
-
     @Override
     public Object apply(GroupResource resource, PutMember.Input input)
         throws AuthException, MethodNotAllowedException, BadRequestException,
@@ -232,11 +222,6 @@ class AddMembers implements RestModifyView<GroupResource, Input> {
       this.get = get;
     }
 
-    @Override
-    public Class<PutMember.Input> inputType() {
-      return PutMember.Input.class;
-    }
-
     @Override
     public Object apply(MemberResource resource, PutMember.Input input) {
       // Do nothing, the user is already a member.

gerrit-server/src/main/java/com/google/gerrit/server/group/CreateGroup.java

@@ -56,11 +56,6 @@ public class CreateGroup implements RestModifyView<TopLevelResource, Input> {
     this.visibleToAll = cfg.getBoolean("groups", "newGroupsVisibleToAll", false);
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public GroupInfo apply(TopLevelResource resource, Input input)
       throws AuthException, BadRequestException, OrmException,

gerrit-server/src/main/java/com/google/gerrit/server/group/DeleteMembers.java

@@ -61,11 +61,6 @@ public class DeleteMembers implements RestModifyView<GroupResource, Input> {
     this.self = self;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(GroupResource resource, Input input)
       throws AuthException, MethodNotAllowedException, BadRequestException,
@@ -159,11 +154,6 @@ public class DeleteMembers implements RestModifyView<GroupResource, Input> {
       this.delete = delete;
     }
 
-    @Override
-    public Class<Input> inputType() {
-      return DeleteMember.Input.class;
-    }
-
     @Override
     public Object apply(MemberResource resource, Input input)
         throws AuthException, MethodNotAllowedException, BadRequestException,

gerrit-server/src/main/java/com/google/gerrit/server/plugins/DisablePlugin.java

@@ -33,11 +33,6 @@ class DisablePlugin implements RestModifyView<PluginResource, Input> {
     this.loader = loader;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(PluginResource resource, Input input) {
     String name = resource.getName();

gerrit-server/src/main/java/com/google/gerrit/server/plugins/EnablePlugin.java

@@ -37,11 +37,6 @@ class EnablePlugin implements RestModifyView<PluginResource, Input> {
     this.loader = loader;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(PluginResource resource, Input input)
       throws ResourceConflictException {

gerrit-server/src/main/java/com/google/gerrit/server/plugins/InstallPlugin.java

@@ -51,11 +51,6 @@ class InstallPlugin implements RestModifyView<TopLevelResource, Input> {
     this.created = created;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Response<ListPlugins.PluginInfo> apply(TopLevelResource resource,
       Input input) throws BadRequestException, IOException {
@@ -105,11 +100,6 @@ class InstallPlugin implements RestModifyView<TopLevelResource, Input> {
       this.loader = loader;
     }
 
-    @Override
-    public Class<Input> inputType() {
-      return Input.class;
-    }
-
     @Override
     public Response<ListPlugins.PluginInfo> apply(PluginResource resource,
         Input input) throws BadRequestException, IOException {

gerrit-server/src/main/java/com/google/gerrit/server/plugins/ReloadPlugin.java

@@ -37,11 +37,6 @@ class ReloadPlugin implements RestModifyView<PluginResource, Input> {
     this.loader = loader;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(PluginResource resource, Input input) throws ResourceConflictException {
     String name = resource.getName();

gerrit-server/src/main/java/com/google/gerrit/server/project/DeleteDashboard.java

@@ -35,11 +35,6 @@ class DeleteDashboard implements RestModifyView<DashboardResource, Input> {
     this.defaultSetter = defaultSetter;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(DashboardResource resource, Input input)
       throws AuthException, BadRequestException, ResourceConflictException,

gerrit-server/src/main/java/com/google/gerrit/server/project/SetDashboard.java

@@ -38,11 +38,6 @@ class SetDashboard implements RestModifyView<DashboardResource, Input> {
     this.defaultSetter = defaultSetter;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(DashboardResource resource, Input input)
       throws AuthException, BadRequestException, ResourceConflictException,

gerrit-server/src/main/java/com/google/gerrit/server/project/SetDefaultDashboard.java

@@ -55,11 +55,6 @@ class SetDefaultDashboard implements RestModifyView<DashboardResource, Input> {
     this.get = get;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(DashboardResource resource, Input input)
       throws AuthException, BadRequestException, ResourceConflictException,
@@ -137,11 +132,6 @@ class SetDefaultDashboard implements RestModifyView<DashboardResource, Input> {
       this.setDefault = setDefault;
     }
 
-    @Override
-    public Class<Input> inputType() {
-      return SetDashboard.Input.class;
-    }
-
     @Override
     public Object apply(ProjectResource resource, Input input)
         throws AuthException, BadRequestException, ResourceConflictException,

gerrit-server/src/main/java/com/google/gerrit/server/project/SetDescription.java

@@ -53,11 +53,6 @@ class SetDescription implements RestModifyView<ProjectResource, Input> {
     this.gitMgr = gitMgr;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(ProjectResource resource, Input input)
       throws AuthException, BadRequestException, ResourceConflictException,

gerrit-server/src/main/java/com/google/gerrit/server/project/SetParent.java

@@ -53,11 +53,6 @@ class SetParent implements RestModifyView<ProjectResource, Input> {
     this.allProjects = allProjects;
   }
 
-  @Override
-  public Class<Input> inputType() {
-    return Input.class;
-  }
-
   @Override
   public Object apply(ProjectResource resource, Input input)
       throws AuthException, BadRequestException, ResourceConflictException,