5 Catalyst::UTF8 - All About UTF8 and Catalyst Encoding
9 Starting in 5.90080 L<Catalyst> will enable UTF8 encoding by default for
10 text like body responses. In addition we've made a ton of fixes around encoding
11 and utf8 scattered throughout the codebase. This document attempts to give
12 an overview of the assumptions and practices that L<Catalyst> uses when
13 dealing with UTF8 and encoding issues. You should also review the
14 Changes file, L<Catalyst::Delta> and L<Catalyst::Upgrading> for more.
16 We attempt to describe all relevant processes, try to give some advice
17 and explain where we may have been exceptional to respect our commitment
18 to backwards compatibility.
20 =head1 UTF8 in Controller Actions
22 Using UTF8 characters in your Controller classes and actions.
26 In this section we will review changes to how UTF8 characters can be used in
27 controller actions, how it looks in the debugging screens (and your logs)
28 as well as how you construct L<URL> objects to actions with UTF8 paths
29 (or using UTF8 args or captures).
31 =head2 Unicode in Controllers and URLs
33 package MyApp::Controller::Root;
36 use base 'Catalyst::Controller';
38 sub heart_with_arg :Path('♥') Args(1) {
39 my ($self, $c, $arg) = @_;
42 sub base :Chained('/') CaptureArgs(0) {
46 sub capture :Chained('base') PathPart('♥') CaptureArgs(1) {
47 my ($self, $c, $capture) = @_;
50 sub arg :Chained('capture') PathPart('♥') Args(1) {
51 my ($self, $c, $arg) = @_;
56 In the example controller above we have constructed two matchable URL routes:
58 http://localhost/root/♥/{arg}
59 http://localhost/base/♥/{capture}/♥/{arg}
61 The first one is a classic Path type action and the second uses Chaining, and
62 spans three actions in total. As you can see, you can use unicode characters
63 in your Path and PathPart attributes (remember to use the C<utf8> pragma to allow
64 these multibyte characters in your source). The two constructed matchable routes
65 would match the following incoming URLs:
67 (heart_with_arg) -> http://localhost/root/%E2%99%A5/{arg}
68 (base/capture/arg) -> http://localhost/base/%E2%99%A5/{capture}/%E2%99%A5/{arg}
70 That path path C<%E2%99%A5> is url encoded unicode (assuming you are hitting this with
71 a reasonably modern browser). Its basically what goes over HTTP when your type a
72 browser location that has the unicode 'heart' in it. However we will use the unicode
73 symbol in your debugging messages:
75 [debug] Loaded Path actions:
76 .-------------------------------------+--------------------------------------.
78 +-------------------------------------+--------------------------------------+
79 | /root/♥/* | /root/heart_with_arg |
80 '-------------------------------------+--------------------------------------'
82 [debug] Loaded Chained actions:
83 .-------------------------------------+--------------------------------------.
84 | Path Spec | Private |
85 +-------------------------------------+--------------------------------------+
86 | /base/♥/*/♥/* | /root/base (0) |
87 | | -> /root/capture (1) |
89 '-------------------------------------+--------------------------------------'
91 And if the requested URL uses unicode characters in your captures or args (such as
92 C<http://localhost:/base/♥/♥/♥/♥>) you should see the arguments and captures as their
93 unicode characters as well:
95 [debug] Arguments are "♥"
96 [debug] "GET" request for "base/♥/♥/♥/♥" from "127.0.0.1"
97 .------------------------------------------------------------+-----------.
99 +------------------------------------------------------------+-----------+
100 | /root/base | 0.000080s |
101 | /root/capture | 0.000075s |
102 | /root/arg | 0.000755s |
103 '------------------------------------------------------------+-----------'
105 Again, remember that we are display the unicode character and using it to match actions
106 containing such multibyte characters BUT over HTTP you are getting these as URL encoded
107 bytes. For example if you looked at the L<PSGI> C<$env> value for C<REQUEST_URI> you
108 would see (for the above request)
110 REQUEST_URI => "/base/%E2%99%A5/%E2%99%A5/%E2%99%A5/%E2%99%A5"
112 So on the incoming request we decode so that we can match and display unicode characters
113 (after decoding the URL encoding). This makes it straightforward to use these types of
114 multibyte characters in your actions and see them incoming in captures and arguments. Please
115 keep this in might if you are doing for example regular expression matching, length determination
116 or other string comparisons, you will need to try these incoming variables as though UTF8
117 strings. For example in the following action:
119 sub arg :Chained('capture') PathPart('♥') Args(1) {
120 my ($self, $c, $arg) = @_;
123 when $arg is "♥" you should expect C<length($arg)> to be C<1> since it is indeed one character
124 although it will take more than one byte to store.
126 =head2 UTF8 in constructing URLs via $c->uri_for
128 For the reverse (constructing meaningful URLs to actions that contain multibyte characters
129 in their paths or path parts, or when you want to include such characters in your captures
130 or arguments) L<Catalyst> will do the right thing (again just remember to use the C<utf8>
134 my $url = $c->uri_for( $c->controller('Root')->action_for('arg'), ['♥','♥']);
136 When you stringify this object (for use in a template, for example) it will automatically
137 do the right thing regarding utf8 encoding and url encoding.
139 http://localhost/base/%E2%99%A5/%E2%99%A5/%E2%99%A5/%E2%99%A5
141 Since again what you want is a properly url encoded version of this. In this case your string
142 length will reflect URL encoded bytes, not the character length. Ultimately what you want
143 to send over the wire via HTTP needs to be bytes.
145 =head1 UTF8 in GET Query and Form POST
147 What Catalyst does with UTF8 in your GET and classic HTML Form POST
149 =head2 UTF8 in URL query and keywords
151 The same rules that we find in URL paths also cover URL query parts. That is
152 if one types a URL like this into the browser
154 http://localhost/example?♥=♥♥
156 When this goes 'over the wire' to your application server its going to be as
157 percent encoded bytes:
160 http://localhost/example?%E2%99%A5=%E2%99%A5%E2%99%A5
162 When L<Catalyst> encounters this we decode the percent encoding and the utf8
163 so that we can properly display this information (such as in the debugging
164 logs or in a response.)
166 [debug] Query Parameters are:
167 .-------------------------------------+--------------------------------------.
168 | Parameter | Value |
169 +-------------------------------------+--------------------------------------+
171 '-------------------------------------+--------------------------------------'
173 All the values and keys that are part of $c->req->query_parameters will be
174 utf8 decoded. So you should not need to do anything special to take those
175 values/keys and send them to the body response (since as we will see later
176 L<Catalyst> will do all the necessary encoding for you).
178 Again, remember that values of your parameters are now decode into Unicode strings. so
179 for example you'd expect the result of length to reflect the character length not
182 Just like with arguments and captures, you can use utf8 literals (or utf8
183 strings) in $c->uri_for:
186 my $url = $c->uri_for( $c->controller('Root')->action_for('example'), {'♥' => '♥♥'});
188 When you stringify this object (for use in a template, for example) it will automatically
189 do the right thing regarding utf8 encoding and url encoding.
191 http://localhost/example?%E2%99%A5=%E2%99%A5%E2%99%A5
193 Since again what you want is a properly url encoded version of this. Ultimately what you want
194 to send over the wire via HTTP needs to be bytes (not unicode characters).
196 Remember if you use any utf8 literals in your source code, you should use the
199 =head2 UTF8 in Form POST
201 In general most modern browsers will follow the specification, which says that POSTed
202 form fields should be encoded in the same way that the document was served with. That means
203 that if you are using modern Catalyst and serving UTF8 encoded responses, a browser is
204 supposed to notice that and encode the form POSTs accordingly.
206 As a result since L<Catalyst> now serves UTF8 encoded responses by default, this means that
207 you can mostly rely on incoming form POSTs to be so encoded. L<Catalyst> will make this
208 assumption and decode accordingly (unless you explicitly turn off encoding...) If you are
209 running Catalyst in developer debug, then you will see the correct unicode characters in
210 the debug output. For example if you generate a POST request:
212 use Catalyst::Test 'MyApp';
215 my $res = request POST "/example/posted", ['♥'=>'♥', '♥♥'=>'♥'];
217 Running in CATALYST_DEBUG=1 mode you should see output like this:
219 [debug] Body Parameters are:
220 .-------------------------------------+--------------------------------------.
221 | Parameter | Value |
222 +-------------------------------------+--------------------------------------+
225 '-------------------------------------+--------------------------------------'
227 And if you had a controller like this:
229 package MyApp::Controller::Example;
231 use base 'Catalyst::Controller';
233 sub posted :POST Local {
235 $c->res->content_type('text/plain');
236 $c->res->body("hearts => ${\$c->req->post_parameters->{♥}}");
239 The following test case would be true:
241 use Encode 2.21 'decode_utf8';
242 is decode_utf8($req->content), 'hearts => ♥';
244 In this case we decode so that we can print and compare strings with multibyte characters.
246 B<NOTE> In some cases some browsers may not follow the specification and set the form POST
247 encoding based on the server response. Catalyst itself doesn't attempt any workarounds, but one
248 common approach is to use a hidden form field with a UTF8 value (You might be familiar with
249 this from how Ruby on Rails has HTML form helpers that do that automatically). In that case
250 some browsers will send UTF8 encoded if it notices the hidden input field contains such a
251 character. Also, you can add an HTML attribute to your form tag which many modern browsers
252 will respect to set the encoding (accept-charset="utf-8"). And lastly there are some javascript
253 based tricks and workarounds for even more odd cases (just search the web for this will return
254 a number of approaches. Hopefully as more compliant browsers become popular these edge cases
257 B<NOTE> It is possible for a form POST multipart response (normally a file upload) to contain
258 inline content with mixed content character sets and encoding. For example one might create
262 use HTTP::Request::Common;
265 my $shiftjs = 'test テスト';
266 my $req = POST '/root/echo_arg',
267 Content_Type => 'form-data',
269 arg0 => 'helloworld',
270 Encode::encode('UTF-8','♥') => Encode::encode('UTF-8','♥♥'),
273 'Content-Type' =>'text/plain; charset=UTF-8',
274 'Content' => Encode::encode('UTF-8', $utf8)],
277 'Content-Type' =>'text/plain; charset=SHIFT_JIS',
278 'Content' => Encode::encode('SHIFT_JIS', $shiftjs)],
281 'Content-Type' =>'text/plain; charset=SHIFT_JIS',
282 'Content' => Encode::encode('SHIFT_JIS', $shiftjs)],
285 In this case we've created a POST request but each part specifies its own content
286 character set (and setting a content encoding would also be possible). Generally one
287 would not run into this situation in a web browser context but for completeness sake
288 Catalyst will notice if a multipart POST contains parts with complex or extended
289 header information and in those cases it will not attempt to apply decoding to the
290 form values. Instead the part will be represented as an instance of an object
291 L<Catalyst::Request::PartData> which will contain all the header information needed
292 for you to perform custom parser of the data.
294 =head1 UTF8 Encoding in Body Response
296 When does L<Catalyst> encode your response body and what rules does it use to
297 determine when that is needed.
305 package MyApp::Controller::Root;
307 use base 'Catalyst::Controller';
310 sub scalar_body :Local {
312 $c->response->content_type('text/html');
313 $c->response->body("<p>This is scalar_body action ♥</p>");
316 sub stream_write :Local {
318 $c->response->content_type('text/html');
319 $c->response->write("<p>This is stream_write action ♥</p>");
322 sub stream_write_fh :Local {
324 $c->response->content_type('text/html');
326 my $writer = $c->res->write_fh;
327 $writer->write_encoded('<p>This is stream_write_fh action ♥</p>');
331 sub stream_body_fh :Local {
333 my $path = File::Spec->catfile('t', 'utf8.txt');
334 open(my $fh, '<', $path) || die "trouble: $!";
335 $c->response->content_type('text/html');
336 $c->response->body($fh);
341 Beginning with L<Catalyst> version 5.90080 You no longer need to set the encoding
342 configuration (although doing so won't hurt anything).
344 Currently we only encode if the content type is one of the types which generally expects a
345 UTF8 encoding. This is determined by the following regular expression:
347 our $DEFAULT_ENCODE_CONTENT_TYPE_MATCH = qr{text|xml$|javascript$};
348 $c->response->content_type =~ /$DEFAULT_ENCODE_CONTENT_TYPE_MATCH/
350 This is a global variable in L<Catalyst::Response> which is stored in the C<encodable_content_type>
351 attribute of $c->response. You may currently alter this directly on the response or globally. In
352 the future we may offer a configuration setting for this.
354 This would match content-types like the following (examples)
359 application/javascript
361 application/vnd.user+xml
363 You should set your content type prior to header finalization if you want L<Catalyst> to
366 B<NOTE> We do not attempt to encode C<application/json> since the two most commonly used
367 approaches (L<Catalyst::View::JSON> and L<Catalyst::Action::REST>) have already configured
368 their JSON encoders to produce properly encoding UTF8 responses. If you are rolling your
369 own JSON encoding, you may need to set the encoder to do the right thing (or override
370 the global regular expression to include the JSON media type).
372 =head2 Encoding with Scalar Body
374 L<Catalyst> supports several methods of supplying your response with body content. The first
375 and currently most common is to set the L<Catalyst::Response> ->body with a scalar string (
380 sub scalar_body :Local {
382 $c->response->content_type('text/html');
383 $c->response->body("<p>This is scalar_body action ♥</p>");
386 In general you should need to do nothing else since L<Catalyst> will automatically encode
387 this string during body finalization. The only matter to watch out for is to make sure
388 the string has not already been encoded, as this will result in double encoding errors.
390 B<NOTE> pay attention to the content-type setting in the example. L<Catalyst> inspects that
391 content type carefully to determine if the body needs encoding).
393 B<NOTE> If you set the character set of the response L<Catalyst> will skip encoding IF the
394 character set is set to something that doesn't match $c->encoding->mime_name. We will assume
395 if you are setting an alternative character set, that means you want to handle the encoding
396 yourself. However it might be easier to set $c->encoding for a given response cycle since
397 you can override this for a given response. For example here's how to override the default
398 encoding and set the correct character set in the response:
400 sub override_encoding :Local {
402 $c->res->content_type('text/plain');
403 $c->encoding(Encode::find_encoding('Shift_JIS'));
404 $c->response->body("テスト");
407 This will use the alternative encoding for a single response.
409 B<NOTE> If you manually set the content-type character set to whatever $c->encoding->mime_name
410 is set to, we STILL encode, rather than assume your manual setting is a flag to override. This
411 is done to support backward compatible assumptions (in particular L<Catalyst::View::TT> has set
412 a utf-8 character set in its default content-type for ages, even though it does not itself do any
413 encoding on the body response). If you are going to handle encoding manually you may set
414 $c->clear_encoding for a single request response cycle, or as in the above example set an alternative
417 =head2 Encoding with streaming type responses
419 L<Catalyst> offers two approaches to streaming your body response. Again, you must remember
420 to set your content type prior to streaming, since invoking a streaming response will automatically
421 finalize and send your HTTP headers (and your content type MUST be one that matches the regular
422 expression given above.)
424 Also, if you are going to override $c->encoding (or invoke $c->clear_encoding), you should do
425 that before anything else!
427 The first streaming method is to use the C<write> method on the response object. This method
428 allows 'inlined' streaming and is generally used with blocking style servers.
430 sub stream_write :Local {
432 $c->response->content_type('text/html');
433 $c->response->write("<p>This is stream_write action ♥</p>");
436 You may call the C<write> method as often as you need to finish streaming all your content.
437 L<Catalyst> will encode each line in turn as long as the content-type meets the 'encodable types'
438 requirement and $c->encoding is set (which it is, as long as you did not change it).
440 B<NOTE> If you try to change the encoding after you start the stream, this will invoke an error
441 response. However since you've already started streaming this will not show up as an HTTP error
442 status code, but rather error information in your body response and an error in your logs.
444 The second way to stream a response is to get the response writer object and invoke methods
447 sub stream_write_fh :Local {
449 $c->response->content_type('text/html');
451 my $writer = $c->res->write_fh;
452 $writer->write_encoded('<p>This is stream_write_fh action ♥</p>');
456 This can be used just like the C<write> method, but typically you request this object when
457 you want to do a nonblocking style response since the writer object can be closed over or
458 sent to a model that will invoke it in a non blocking manner. For more on using the writer
459 object for non blocking responses you should review the C<Catalyst> documentation and also
460 you can look at several articles from last years advent, in particular:
462 L<http://www.catalystframework.org/calendar/2013/10>, L<http://www.catalystframework.org/calendar/2013/11>,
463 L<http://www.catalystframework.org/calendar/2013/12>, L<http://www.catalystframework.org/calendar/2013/13>,
464 L<http://www.catalystframework.org/calendar/2013/14>.
466 The main difference this year is that previously calling ->write_fh would return the actual
467 L<Plack> writer object that was supplied by your plack application handler, whereas now we wrap
468 that object in a lightweight decorator object that proxies the C<write> and C<close> methods
469 and supplies an additional C<write_encoded> method. C<write_encoded> does the exact same thing
470 as C<write> except that it will first encode the string when necessary. In general if you are
471 streaming encodable content such as HTML this is the method to use. If you are streaming
472 binary content, you should just use the C<write> method (although if the content type is set
473 correctly we would skip encoding anyway, but you may as well avoid the extra noop overhead).
475 The last style of content response that L<Catalyst> supports is setting the body to a filehandle
476 like object. In this case the object is passed down to the Plack application handler directly
477 and currently we do nothing to set encoding.
479 sub stream_body_fh :Local {
481 my $path = File::Spec->catfile('t', 'utf8.txt');
482 open(my $fh, '<', $path) || die "trouble: $!";
483 $c->response->content_type('text/html');
484 $c->response->body($fh);
487 In this example we create a filehandle to a text file that contains UTF8 encoded characters. We
488 pass this down without modification, which I think is correct since we don't want to double
489 encode. However this may change in a future development release so please be sure to double
490 check the current docs and changelog. Its possible a future release will require you to to set
491 a encoding on the IO layer level so that we can be sure to properly encode at body finalization.
492 So this is still an edge case we are writing test examples for. But for now if you are returning
493 a filehandle like response, you are expected to make sure you are following the L<PSGI> specification
494 and return raw bytes.
496 =head2 Override the Encoding on Context
498 As already noted you may change the current encoding (or remove it) by setting an alternative
499 encoding on the context;
501 $c->encoding(Encode::find_encoding('Shift_JIS'));
503 Please note that you can continue to change encoding UNTIL the headers have been finalized. The
504 last setting always wins. Trying to change encoding after header finalization is an error.
506 =head2 Setting the Content Encoding HTTP Header
508 In some cases you may set a content encoding on your response. For example if you are encoding
509 your response with gzip. In this case you are again on your own. If we notice that the
510 content encoding header is set when we hit finalization, we skip automatic encoding:
519 $c->res->content_type('text/plain');
520 $c->res->content_type_charset('UTF-8');
521 $c->res->content_encoding('gzip');
524 Compress::Zlib::memGzip(
525 Encode::encode_utf8("manual_1 ♥")));
529 If you are using L<Catalyst::Plugin::Compress> you need to upgrade to the most recent version
530 in order to be compatible with changes introduced in L<Catalyst> 5.90080. Other plugins may
531 require updates (please open bugs if you find them).
533 B<NOTE> Content encoding may be set to 'identify' and we will still perform automatic encoding
534 if the content type is encodable and an encoding is present for the context.
536 =head2 Using Common Views
538 The following common views have been updated so that their tests pass with default UTF8
539 encoding for L<Catalyst>:
541 L<Catalyst::View::TT>, L<Catalyst::View::Mason>, L<Catalyst::View::HTML::Mason>,
542 L<Catalyst::View::Xslate>
544 See L<Catalyst::Upgrading> for additional information on L<Catalyst> extensions that require
547 In generally for the common views you should not need to do anything special. If your actual
548 template files contain UTF8 literals you should set configuration on your View to enable that.
549 For example in TT, if your template has actual UTF8 character in it you should do the following:
551 MyApp::View::TT->config(ENCODING => 'utf-8');
553 However L<Catalyst::View::Xslate> wants to do the UTF8 encoding for you (We assume that the
554 authors of that view did this as a workaround to the fact that until now encoding was not core
555 to L<Catalyst>. So if you use that view, you either need to tell it to not encode, or you need
556 to turn off encoding for Catalyst.
558 MyApp::View::Xslate->config(encode_body => 0);
562 MyApp->config(encoding=>undef);
564 Preference is to disable it in the View.
566 Other views may be similar. You should review View documentation and test during upgrading.
567 We tried to make sure most common views worked properly and noted all workaround but if we
568 missed something please alert the development team (instead of introducing a local hack into
569 your application that will mean nobody will ever upgrade it...).
571 =head2 Setting the response from an external PSGI application.
573 L<Catalyst::Response> allows one to set the response from an external L<PSGI> application.
574 If you do this, and that external application sets a character set on the content-type, we
575 C<clear_encoding> for the rest of the response. This is done to prevent double encoding.
577 B<NOTE> Even if the character set of the content type is the same as the encoding set in
578 $c->encoding, we still skip encoding. This is a regrettable difference from the general rule
579 outlined above, where if the current character set is the same as the current encoding, we
580 encode anyway. Nevertheless I think this is the correct behavior since the earlier rule exists
581 only to support backward compatibility with L<Catalyst::View::TT>.
583 In general if you want L<Catalyst> to handle encoding, you should avoid setting the content
584 type character set since Catalyst will do so automatically based on the requested response
585 encoding. Its best to request alternative encodings by setting $c->encoding and if you really
586 want manual control of encoding you should always $c->clear_encoding so that programmers that
587 come after you are very clear as to your intentions.
589 =head2 Disabling default UTF8 encoding
591 You may encounter issues with your legacy code running under default UTF8 body encoding. If
592 so you can disable this with the following configurations setting:
594 MyApp->config(encoding=>undef);
596 Where C<MyApp> is your L<Catalyst> subclass.
598 If you do not wish to disable all the Catalyst encoding features, you may disable specific
599 features via two additional configuration options: 'skip_body_param_unicode_decoding'
600 and 'skip_complex_post_part_handling'. The first will skip any attempt to decode POST
601 parameters in the creating of body parameters and the second will skip creation of instances
602 of L<Catalyst::Request::PartData> in the case that the multipart form upload contains parts
603 with a mix of content character sets.
605 If you believe you have discovered a bug in UTF8 body encoding, I strongly encourage you to
606 report it (and not try to hack a workaround in your local code). We also recommend that you
607 regard such a workaround as a temporary solution. It is ideal if L<Catalyst> extension
608 authors can start to count on L<Catalyst> doing the write thing for encoding.
612 This document has attempted to be a complete review of how UTF8 and encoding works in the
613 current version of L<Catalyst> and also to document known issues, gotchas and backward
614 compatible hacks. Please report issues to the development team.
618 John Napiorkowski L<jjnapiork@cpan.org|email:jjnapiork@cpan.org>