Cleanup implementation of REST views

- specify return type if possible
- remove unnecessary throw declarations
- convert some of the thrown exceptions to RestExceptions
- do not throw Exception but specific exceptions
- sort throw declarations (first RestExceptions, then other
  exceptions)

Having explicit return types and exceptions makes it easier to
programatically invoke the REST views, e.g. if a plugin wants to add a
REST view that wraps a Gerrit core REST view.

Change-Id: I5c59553b6cfad457f7ec037cceb08936247bf8e8
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

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

@@ -15,6 +15,7 @@
 package com.google.gerrit.server.change;
 
 import com.google.gerrit.extensions.restapi.CacheControl;
+import com.google.gerrit.extensions.restapi.ResourceNotFoundException;
 import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.server.change.ChangeJson.CommitInfo;
@@ -34,11 +35,16 @@ public class GetCommit implements RestReadView<RevisionResource> {
 
   @Override
   public Response<CommitInfo> apply(RevisionResource resource)
-      throws OrmException, PatchSetInfoNotAvailableException {
-    Response<CommitInfo> r = Response.ok(json.toCommit(resource.getPatchSet()));
-    if (resource.isCacheable()) {
-      r.caching(CacheControl.PRIVATE(7, TimeUnit.DAYS));
+      throws ResourceNotFoundException, OrmException {
+    try {
+      Response<CommitInfo> r =
+          Response.ok(json.toCommit(resource.getPatchSet()));
+      if (resource.isCacheable()) {
+        r.caching(CacheControl.PRIVATE(7, TimeUnit.DAYS));
+      }
+      return r;
+    } catch (PatchSetInfoNotAvailableException e) {
+      throw new ResourceNotFoundException(e.getMessage());
     }
-    return r;
   }
 }