The lack of customizability for the google formatter concerns me,
especially once we start thinking about GeoServer (and I am also not a fan
of enforced two-space indentation). I'll also echo Ben's comment about
idempotency, that is a significant concern.

In particular, the Spring MVC Controllers in GeoServer have some
nonstandard indentation that is included primarily for the sake of code
clarity, e.g:

I believe there are other similar structures elsewhere that skirt the
boundaries of our current rules for sake of readability (such as large
boolean logic expressions, inline comments indented to be in line with
applicable code, large concatenated string blocks indented to be more
readable, and others), although I don't have any specific examples at the
A formatter which allows for customizability should be able to preserve
this sort of stuff, but one that isn't

I tried out the Intellij formatter on GeoServer on OS X, and a couple notes
(branch <>):

   - It took 4 minutes to format all of GeoServer
   - Running the formatter a second time took 2.5 minutes, and altered 5
   so not quite idempotent. A third time showed no changes, so it is likely
   that the initial formatting changes caused changes that required further
   formatting. Overall, not likely to be a serious issue.
   - I had to use slightly different command syntax - notably I needed the
   full path to the source directory, at the end of the command:

<idea>/bin/ -r -m "*.java,pom.xml" -s
<gs_source>/workspace/formatter.xml <gs_source>/geoserver/src

   - The Intellij formatter preserved the argline example in
   LayerController linked above as-is.

I also tried the fmt-maven-plugin on GeoServer (branch

   - Since its part of the build, not quite sure how fast it was, but
   seemed pretty fast; full GeoServer build with reformatting (skipping tests)
   took 3 minutes (And I think maven downloaded a few jars .
   - Second pass of formatting changed 6 files
   Third pass changed none, so the current version seems to be adequate with
   respect to idempotency.
   - Looking at some of the changes made, we get stuff like this:

    String groupSearchFilter; //more appropriate name would be
groupMembershipFilter - XStream backwards compatibility


         groupSearchFilter; // more appropriate name would be
   groupMembershipFilter - XStream backwards
     // compatibility

   Which seems to be pretty bad formatting. So that is a mark against the
   google formatter.

   - Formatting retained adequate legibility with respect to the argline
   example, by automatically moving the first argument to a newline, so that
   is promising:

@PutMapping(value = "/{layerName}")
public void layerPut(
    @RequestBody LayerInfo layer,
    @PathVariable String layerName,
    @PathVariable(required = false) String workspaceName) {

Overall, I think I prefer the Intellij formatter, due to customizability
and four-space indentation.


On Sun, Mar 11, 2018 at 1:45 PM, Ben Caradoc-Davies <>

> Andrea,
> the Google formatter looks like the strongest candidate, despite my
> sharing your lack of fondness for two-space indentation.
> (1) Is it idempotent? That is, if you run the formatter a second time,
> does it change anything? There are some outstanding issues:
> (2) Do we have a plan for Eclipse formatter:off and formatter:on tags?
> This is also discussed:
> Thanks for the interesting review of these tools. You had a fun weekend!
> Kind regards,
> Ben.
> On 11/03/18 22:54, Andrea Aime wrote:
>> Hi,
>> I've been experimenting a bit with mass code base reformats approaches on
>> GeoTools (used as a guinea
>> pig and hoping to transfer the same approach on GeoWebCache and Geoserver
>> too, hence the
>> cross post).
>> I wrote a document to share my findings here (read only, but can be
>> commented on), along with links
>> to branches where the reformatting happened:
>> F5j9Zho-Jo5O_dXvI-Y/edit#
>> Originally I was thinking of approaching mass reformat in a code sprint,
>> but since we have none planned,
>> a "lightweight" approach doing the smallest amount of work for the
>> greatest
>> benefit seems also
>> feasible.
>> Of the reformat approaches above, I cannot argue with the tooling and
>> effectiveness of the Google style one,
>> but indenting only 2 spaces leaves me a bit "cold", the code is flatter
>> and
>> structures seem harder to
>> locate... it may well be just a matter of habit.
>> The intellij command line one + checkstyle changes our approach to
>> formatting less, but will
>> require more manual work on setting up checkstyle the way we want it, and
>> seems to have more
>> overhead
>> So... would you like to see one of these actually committed and enforced?
>> Expressions of interest to help in this endeavor?
>> Cheers
>> Andrea
>> ==
>> GeoServer Professional Services from the experts! Visit
>> for more information.
>> ==
>> Ing. Andrea Aime
>> @geowolf
>> Technical Lead
>> GeoSolutions S.A.S.
>> Via di Montramito 3/A
>> 55054  Massarosa (LU)
>> phone: +39 0584 962313
>> fax: +39 0584 1660272
>> mob: +39 339 8844549
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> Ben Caradoc-Davies <>
> Director
> Transient Software Limited <>
> New Zealand
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