1 .. -*- coding: utf-8 -*- |
|
2 |
|
3 Concepts |
|
4 -------- |
|
5 |
|
6 This section aims to provide you the keys of success with `CubicWeb` |
|
7 by clarifying the terms specific to our framework. |
|
8 |
|
9 Global architecture |
|
10 ~~~~~~~~~~~~~~~~~~~ |
|
11 .. image:: images/archi_globale.en.png |
|
12 |
|
13 |
|
14 `CubicWeb` framework is a server/client application framework. Those two |
|
15 parts communicate through RQL (`CubicWeb` query language implementation) |
|
16 and ResultSet (which will be explained in :ref:`TermsVocabulary`). |
|
17 |
|
18 The server manages all interactions with sources. |
|
19 |
|
20 |
|
21 .. note:: |
|
22 Usually, the client and server sides are integrated in the same |
|
23 process and interact directly, without the need for distant |
|
24 calls using Pyro. But, it is important to note that those two |
|
25 sides, client/server, are disjointed and it is possible to execute |
|
26 a couple of calls in distinct processes to balance the load of |
|
27 your web site on one or more machines. |
|
28 |
|
29 .. _TermsVocabulary: |
|
30 |
|
31 Terms and vocabulary |
|
32 ~~~~~~~~~~~~~~~~~~~~~ |
|
33 |
|
34 `CubicWeb` defines its own terminology. To make sure there is no confusion |
|
35 while reading this book, we strongly recommand you take time to go through |
|
36 the following definitions that are the basics to understand while |
|
37 developing with `CubicWeb`. |
|
38 |
|
39 *schema* |
|
40 The schema defines the data model of an application based on entities |
|
41 and relations, modeled with a comprehensive language made of Python |
|
42 classes based on `yams`_ library. This is the core piece |
|
43 of an application. It is initially defined in the file system and is |
|
44 stored in the database at the time an instance is created. `CubicWeb` |
|
45 provides a certain number of system entities included automatically |
|
46 (necessary for the core of `CubicWeb`) and a library of |
|
47 cubes (which defined application entities) that can be explicitely |
|
48 included if necessary. |
|
49 |
|
50 *entity type* |
|
51 An entity type is a set of attributes; the essential attribute of |
|
52 an entity is its key, named eid. |
|
53 |
|
54 *relation type* |
|
55 Entities are linked to each others by relations. In `CubicWeb` |
|
56 relations are binary: by convention we name the first item of |
|
57 a relation the `subject` and the second the `object`. |
|
58 |
|
59 *final entity type* |
|
60 Final types correspond to the basic types such as string of characters, |
|
61 integers... Those types have a main property which is that they can |
|
62 only be used as `object` of a relation. The attributes of an entity |
|
63 (non final) are entities (finals). |
|
64 |
|
65 *final relation type* |
|
66 A relation is said final if its `object` is a final type. This is equivalent |
|
67 to an entity attribute. |
|
68 |
|
69 *relation definition* |
|
70 A relation definition is a 3-uple (subject entity type, relation type, object |
|
71 entity type), with an associated set of property such as cardinality, constraints... |
|
72 |
|
73 *repository* |
|
74 This is the RQL server side of `CubicWeb`. Be carefull not to get |
|
75 confused with a Mercurial repository or a debian repository. |
|
76 |
|
77 *source* |
|
78 A data source is a container of data (SGBD, LDAP directory, `Google |
|
79 App Engine`'s datastore ...) integrated in the |
|
80 `CubicWeb` repository. This repository has at least one source, `system` which |
|
81 contains the schema of the application, plain-text index and other |
|
82 vital informations for the system. |
|
83 |
|
84 *configuration* |
|
85 It is possible to create different configurations for an instance: |
|
86 |
|
87 - ``repository`` : repository only, accessible for clients using Pyro |
|
88 - ``twisted`` : web interface only, access the repository using Pyro |
|
89 - ``all-in-one`` : web interface and repository in a single process. |
|
90 The repository could be or not accessible using Pyro. |
|
91 |
|
92 *cube* |
|
93 A cube is a model grouping one or multiple data types and/or views |
|
94 to provide a specific functionality or a complete `CubicWeb` application |
|
95 potentially using other cubes. The available cubes are located in the file |
|
96 system at `/path/to/forest/cubicweb/cubes` for a Mercurial forest installation. |
|
97 For a debian packages installation they will be located in |
|
98 `/usr/share/cubicweb/cubes`. |
|
99 Larger applications can be built quite fast by importing cubes, |
|
100 adding entities and relationships, overriding the |
|
101 *views* that display the cubes or by editing informations not provided by |
|
102 the cubes. |
|
103 |
|
104 *instance* |
|
105 An instance is a specific installation of one or multiple cubes. All the required |
|
106 configuration files necessary for the well being of your web application |
|
107 are grouped in an instance. This will refer to the cube(s) your application |
|
108 is based on. |
|
109 For example logilab.org and our intranet are two instances of a single |
|
110 cube "jpl", developped internally. |
|
111 The instances are defined in the directory `/etc/cubicweb.d`. |
|
112 |
|
113 *application* |
|
114 The term application is sometimes used to talk about an instance |
|
115 and sometimes to talk of a cube depending on the context. |
|
116 So we would like to avoid using this term and try to use *cube* and |
|
117 *instance* instead. |
|
118 |
|
119 *result set* |
|
120 This object contains the results of an RQL query sent to the source |
|
121 and informations on the query. |
|
122 |
|
123 *Pyro* |
|
124 `Python Remote Object`_, distributed objects system similar to Java's RMI |
|
125 (Remote Method Invocation), which can be used for the dialog between the web |
|
126 side of the framework and the RQL repository. |
|
127 |
|
128 *query language* |
|
129 A full-blown query language named RQL is used to formulate requests |
|
130 to the database or any sources such as LDAP or `Google App Engine`'s |
|
131 datastore. |
|
132 |
|
133 *views* |
|
134 A view is applied to a `result set` to present it as HTML, XML, |
|
135 JSON, CSV, etc. Views are implemented as Python classes. There is no |
|
136 templating language. |
|
137 |
|
138 *generated user interface* |
|
139 A user interface is generated on-the-fly from the schema definition: |
|
140 entities can be created, displayed, updated and deleted. As display |
|
141 views are not very fancy, it is usually necessary to develop your |
|
142 own. Any generated view can be overridden by defining a new one with |
|
143 the same identifier. |
|
144 |
|
145 *rql* |
|
146 Relation Query Language in order to emphasize the way of browsing relations. |
|
147 This query language is inspired by SQL but is on a higher level; |
|
148 its implementation generates SQL. |
|
149 |
|
150 |
|
151 .. _`Python Remote Object`: http://pyro.sourceforge.net/ |
|
152 .. _`yams`: http://www.logilab.org/project/yams/ |
|
153 |
|
154 |
|
155 `CubicWeb` engine |
|
156 ~~~~~~~~~~~~~~~~~ |
|
157 |
|
158 The engine in `CubicWeb` is a set of classes managing a set of objects loaded |
|
159 dynamically at the startup of `CubicWeb` (*appobjects*). Those dynamic objects, |
|
160 based on the schema or the library, are building the final application. |
|
161 The different dynamic components are for example: |
|
162 |
|
163 * client and server side |
|
164 |
|
165 - entities definition, containing the logic which enables application data manipulation |
|
166 |
|
167 * client side |
|
168 |
|
169 - *views*, or more specifically |
|
170 |
|
171 - boxes |
|
172 - header and footer |
|
173 - forms |
|
174 - page templates |
|
175 |
|
176 - *actions* |
|
177 - *controllers* |
|
178 |
|
179 * server side |
|
180 |
|
181 - notification hooks |
|
182 - notification views |
|
183 |
|
184 The components of the engine are: |
|
185 |
|
186 * a frontal web (only twisted is available so far), transparent for dynamic objects |
|
187 * an object that encapsulates the configuration |
|
188 * a `registry` (`cubicweb.cwvreg`) containing the dynamic objects loaded automatically |
|
189 |
|
190 Every *appobject* may access to the instance configuration using its *config* attribute |
|
191 and to the registry using its *vreg* attribute. |
|
192 |
|
193 API Python/RQL |
|
194 ~~~~~~~~~~~~~~ |
|
195 |
|
196 The Python API developped to interface with RQL is inspired from the standard db-api, |
|
197 with a Connection object having the methods cursor, rollback and commit essentially. |
|
198 The most important method is the `execute` method of a cursor : |
|
199 |
|
200 `execute(rqlstring, args=None, eid_key=None, build_descr=True)` |
|
201 |
|
202 :rqlstring: the RQL query to execute (unicode) |
|
203 :args: if the query contains substitutions, a dictionary containing the values to use |
|
204 :eid_key: |
|
205 an implementation detail of the RQL cache implies that if a substitution |
|
206 is used to introduce an eid *susceptible to raise the ambiguities in the query |
|
207 type resolution*, then we have to specify the corresponding key in the dictionary |
|
208 through this argument |
|
209 |
|
210 |
|
211 The `Connection` object owns the methods `commit` and `rollback`. You *should |
|
212 never need to use them* during the development of the web interface based on |
|
213 the `CubicWeb` framework as it determines the end of the transaction depending |
|
214 on the query execution success. |
|
215 |
|
216 .. note:: |
|
217 While executing update queries (SET, INSERT, DELETE), if a query generates |
|
218 an error related to security, a rollback is automatically done on the current |
|
219 transaction. |
|
220 |
|
221 |
|
222 The `Request` class (`cubicweb.web`) |
|
223 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
|
224 |
|
225 A request instance is created when an HTTP request is sent to the web server. |
|
226 It contains informations such as form parameters, user authenticated, etc. |
|
227 |
|
228 **Globally, a request represents a user query, either through HTTP or not |
|
229 (we also talk about RQL queries on the server side for example).** |
|
230 |
|
231 An instance of `Request` has the following attributes: |
|
232 |
|
233 * `user`, instance of `cubicweb.common.utils.User` corresponding to the authenticated |
|
234 user |
|
235 * `form`, dictionary containing the values of a web form |
|
236 * `encoding`, character encoding to use in the response |
|
237 |
|
238 But also: |
|
239 |
|
240 :Session data handling: |
|
241 * `session_data()`, returns a dictionary containing all the session data |
|
242 * `get_session_data(key, default=None)`, returns a value associated to the given |
|
243 key or the value `default` if the key is not defined |
|
244 * `set_session_data(key, value)`, assign a value to a key |
|
245 * `del_session_data(key)`, suppress the value associated to a key |
|
246 |
|
247 |
|
248 :Cookies handling: |
|
249 * `get_cookie()`, returns a dictionary containing the value of the header |
|
250 HTTP 'Cookie' |
|
251 * `set_cookie(cookie, key, maxage=300)`, adds a header HTTP `Set-Cookie`, |
|
252 with a minimal 5 minutes length of duration by default (`maxage` = None |
|
253 returns a *session* cookie which will expire when the user closes the browser |
|
254 window) |
|
255 * `remove_cookie(cookie, key)`, forces a value to expire |
|
256 |
|
257 :URL handling: |
|
258 * `url()`, returns the full URL of the HTTP request |
|
259 * `base_url()`, returns the root URL of the web application |
|
260 * `relative_path()`, returns the relative path of the request |
|
261 |
|
262 :And more...: |
|
263 * `set_content_type(content_type, filename=None)`, adds the header HTTP |
|
264 'Content-Type' |
|
265 * `get_header(header)`, returns the value associated to an arbitrary header |
|
266 of the HTTP request |
|
267 * `set_header(header, value)`, adds an arbitrary header in the response |
|
268 * `cursor()` returns a RQL cursor on the session |
|
269 * `execute(*args, **kwargs)`, shortcut to ``.cursor().execute()`` |
|
270 * `property_value(key)`, properties management (`CWProperty`) |
|
271 * dictionary `data` to store data to share informations between components |
|
272 *while a request is executed* |
|
273 |
|
274 Please note that this class is abstract and that a concrete implementation |
|
275 will be provided by the *frontend* web used (in particular *twisted* as of |
|
276 today). For the views or others that are executed on the server side, |
|
277 most of the interface of `Request` is defined in the session associated |
|
278 to the client. |
|
279 |
|
280 The `AppObject` class |
|
281 ~~~~~~~~~~~~~~~~~~~~~ |
|
282 |
|
283 In general: |
|
284 |
|
285 * we do not inherit directly from this class but from a more specific |
|
286 class such as `AnyEntity`, `EntityView`, `AnyRsetView`, |
|
287 `Action`... |
|
288 |
|
289 * to be recordable, a subclass has to define its own register (attribute |
|
290 `__registry__`) and its identifier (attribute `id`). Usually we do not have |
|
291 to take care of the register, only the identifier `id`. |
|
292 |
|
293 We can find a certain number of attributes and methods defined in this class |
|
294 and common to all the application objects. |
|
295 |
|
296 At the recording, the following attributes are dynamically added to |
|
297 the *subclasses*: |
|
298 |
|
299 * `vreg`, the `vregistry` of the application |
|
300 * `schema`, the application schema |
|
301 * `config`, the application configuration |
|
302 |
|
303 We also find on instances, the following attributes: |
|
304 |
|
305 * `req`, `Request` instance |
|
306 * `rset`, the *result set* associated to the object if necessary |
|
307 * `cursor`, rql cursor on the session |
|
308 |
|
309 |
|
310 :URL handling: |
|
311 * `build_url(method=None, **kwargs)`, returns an absolute URL based on |
|
312 the given arguments. The *controller* supposed to handle the response, |
|
313 can be specified through the special parameter `method` (the connection |
|
314 is theoretically done automatically :). |
|
315 |
|
316 * `datadir_url()`, returns the directory of the application data |
|
317 (contains static files such as images, css, js...) |
|
318 |
|
319 * `base_url()`, shortcut to `req.base_url()` |
|
320 |
|
321 * `url_quote(value)`, version *unicode safe* of the function `urllib.quote` |
|
322 |
|
323 :Data manipulation: |
|
324 |
|
325 * `etype_rset(etype, size=1)`, shortcut to `vreg.etype_rset()` |
|
326 |
|
327 * `eid_rset(eid, rql=None, descr=True)`, returns a *result set* object for |
|
328 the given eid |
|
329 * `entity(row, col=0)`, returns the entity corresponding to the data position |
|
330 in the *result set* associated to the object |
|
331 |
|
332 * `complete_entity(row, col=0, skip_bytes=True)`, is equivalent to `entity` but |
|
333 also call the method `complete()` on the entity before returning it |
|
334 |
|
335 :Data formatting: |
|
336 * `format_date(date, date_format=None, time=False)` returns a string for a |
|
337 mx date time according to application's configuration |
|
338 * `format_time(time)` returns a string for a mx date time according to |
|
339 application's configuration |
|
340 |
|
341 :And more...: |
|
342 |
|
343 * `external_resource(rid, default=_MARKER)`, access to a value defined in the |
|
344 configuration file `external_resource` |
|
345 |
|
346 * `tal_render(template, variables)`, renders a precompiled page template with |
|
347 variables in the given dictionary as context |
|
348 |
|
349 .. note:: |
|
350 When we inherit from `AppObject` (even not directly), you *always* have to use |
|
351 **super()** to get the methods and attributes of the superclasses, and not |
|
352 use the class identifier. |
|
353 For example, instead of writting: :: |
|
354 |
|
355 class Truc(PrimaryView): |
|
356 def f(self, arg1): |
|
357 PrimaryView.f(self, arg1) |
|
358 |
|
359 You'd better write: :: |
|
360 |
|
361 class Truc(PrimaryView): |
|
362 def f(self, arg1): |
|
363 super(Truc, self).f(arg1) |
|
364 |
|
365 .. _cubesConcepts: |
|
366 |
|
367 Cubes |
|
368 ~~~~~ |
|
369 |
|
370 What is a cube ? |
|
371 ```````````````` |
|
372 |
|
373 A cube is a model grouping one or more entity types and/or views associated |
|
374 in order to provide a specific feature or even a complete application using |
|
375 other cubes. |
|
376 |
|
377 You can decide to write your own set of cubes if you wish to re-use the |
|
378 entity types you develop. Lots of cubes are available from the `CubicWeb |
|
379 Forge`_ under a free software license. |
|
380 |
|
381 .. _`CubicWeb Forge`: http://www.cubicweb.org/project/ |
|
382 |
|
383 .. _foundationsCube: |
|
384 |
|
385 Standard structure for a cube |
|
386 ````````````````````````````` |
|
387 |
|
388 A cube is structured as follows: |
|
389 |
|
390 :: |
|
391 |
|
392 mycube/ |
|
393 | |
|
394 |-- data/ |
|
395 | |-- cubes.mycube.css |
|
396 | |-- cubes.mycube.js |
|
397 | `-- external_resources |
|
398 | |
|
399 |-- debian/ |
|
400 | |-- changelog |
|
401 | |-- compat |
|
402 | |-- control |
|
403 | |-- copyright |
|
404 | |-- cubicweb-mycube.prerm |
|
405 | `-- rules |
|
406 | |
|
407 |-- entities.py |
|
408 | |
|
409 |-- i18n/ |
|
410 | |-- en.po |
|
411 | `-- fr.po |
|
412 | |
|
413 |-- __init__.py |
|
414 | |
|
415 |-- MANIFEST.in |
|
416 | |
|
417 |-- migration/ |
|
418 | |-- postcreate.py |
|
419 | `-- precreate.py |
|
420 | |
|
421 |-- __pkginfo__.py |
|
422 | |
|
423 |-- schema.py |
|
424 | |
|
425 |-- setup.py |
|
426 | |
|
427 |-- site_cubicweb.py |
|
428 | |
|
429 |-- hooks.py |
|
430 | |
|
431 |-- test/ |
|
432 | |-- data/ |
|
433 | | `-- bootstrap_cubes |
|
434 | |-- pytestconf.py |
|
435 | |-- realdb_test_mycube.py |
|
436 | `-- test_mycube.py |
|
437 | |
|
438 `-- views.py |
|
439 |
|
440 |
|
441 We can use subpackages instead of python modules for ``views.py``, ``entities.py``, |
|
442 ``schema.py`` or ``hooks.py``. For example, we could have: |
|
443 |
|
444 :: |
|
445 |
|
446 mycube/ |
|
447 | |
|
448 |-- entities.py |
|
449 |-- hooks.py |
|
450 `-- views/ |
|
451 |-- forms.py |
|
452 |-- primary.py |
|
453 `-- widgets.py |
|
454 |
|
455 |
|
456 where : |
|
457 |
|
458 * ``schema`` contains the schema definition (server side only) |
|
459 * ``entities`` contains the entities definition (server side and web interface) |
|
460 * ``sobjects`` contains hooks and/or views notifications (server side only) |
|
461 * ``views`` contains the web interface components (web interface only) |
|
462 * ``test`` contains tests related to the application (not installed) |
|
463 * ``i18n`` contains message catalogs for supported languages (server side and |
|
464 web interface) |
|
465 * ``data`` contains data files for static content (images, css, javascripts) |
|
466 ...(web interface only) |
|
467 * ``migration`` contains initialization file for new instances (``postcreate.py``) |
|
468 and a file containing dependencies of the component depending on the version |
|
469 (``depends.map``) |
|
470 * ``debian`` contains all the files managing debian packaging (you will find |
|
471 the usual files ``control``, ``rules``, ``changelog``... not installed) |
|
472 * file ``__pkginfo__.py`` provides component meta-data, especially the distribution |
|
473 and the current version (server side and web interface) or sub-cubes used by |
|
474 the cube. |
|
475 |
|
476 |
|
477 At least you should have: |
|
478 |
|
479 * the file ``__pkginfo__.py`` |
|
480 * the schema definition |
|
481 XXX false, we may want to have cubes which are only adding a service, |
|
482 no persistent data (eg embedding for instance) |
|
483 |
|
484 |
|
485 Standard library |
|
486 ```````````````` |
|
487 |
|
488 A library of standard cubes are available from `CubicWeb Forge`_ |
|
489 Cubes provide entities and views. |
|
490 |
|
491 The available application entities are: |
|
492 |
|
493 * addressbook_: PhoneNumber and PostalAddress |
|
494 |
|
495 * basket_: Basket (like a shopping cart) |
|
496 |
|
497 * blog_: Blog (a *very* basic blog) |
|
498 |
|
499 * comment_: Comment (to attach comment threads to entities) |
|
500 |
|
501 * event_: Event (define events, display them in calendars) |
|
502 |
|
503 * file_: File (to allow users to upload and store binary or text files) |
|
504 |
|
505 * folder_: Folder (to organize things but grouping them in folders) |
|
506 |
|
507 * keyword_: Keyword (to define classification schemes) |
|
508 |
|
509 * link_: Link (to collect links to web resources) |
|
510 |
|
511 * mailinglist_: MailingList (to reference a mailing-list and the URLs |
|
512 for its archives and its admin interface) |
|
513 |
|
514 * person_: Person (easily mixed with addressbook) |
|
515 |
|
516 * tag_: Tag (to tag anything) |
|
517 |
|
518 * task_: Task (something to be done between start and stop date) |
|
519 |
|
520 * zone_: Zone (to define places within larger places, for example a |
|
521 city in a state in a country) |
|
522 |
|
523 .. _addressbook: http://www.cubicweb.org/project/cubicweb-addressbook |
|
524 .. _basket: http://www.cubicweb.org/project/cubicweb-basket |
|
525 .. _blog: http://www.cubicweb.org/project/cubicweb-blog |
|
526 .. _comment: http://www.cubicweb.org/project/cubicweb-comment |
|
527 .. _event: http://www.cubicweb.org/project/cubicweb-event |
|
528 .. _file: http://www.cubicweb.org/project/cubicweb-file |
|
529 .. _folder: http://www.cubicweb.org/project/cubicweb-folder |
|
530 .. _keyword: http://www.cubicweb.org/project/cubicweb-keyword |
|
531 .. _link: http://www.cubicweb.org/project/cubicweb-link |
|
532 .. _mailinglist: http://www.cubicweb.org/project/cubicweb-mailinglist |
|
533 .. _person: http://www.cubicweb.org/project/cubicweb-person |
|
534 .. _tag: http://www.cubicweb.org/project/cubicweb-tag |
|
535 .. _task: http://www.cubicweb.org/project/cubicweb-task |
|
536 .. _zone: http://www.cubicweb.org/project/cubicweb-zone |
|