Wiki source code of Velocity Training

Version 37.7 by Vincent Massol on 2021/05/01

version	line-number	content
37.3	1	{{box cssClass="floatinginfobox" title="Contents"}}
37.6	2	{{toc depth="2" start="2"/}}
37.3	3	{{/box}}
	4
1.1	5	= How to use Velocity in XWiki pages =
36.1	6
1.1	7	== What is it? ==
	8
	9	=== ===
	10
	11	* Velocity is a template language.
	12	* It describes what your page should be.
	13	Which means it control what you display**.
	14
	15	Examples:
36.1	16
1.1	17	* display the name of the user
	18	* display an image under certain circonstances only
	19	* display a list of all the blog categories
	20
	21	=== Example ===
36.1	22
32.1	23	{{code language="velocity"}}
34.1	24	{{velocity}}
1.1	25	Welcome $xcontext.user !
	26	#if($hasAdmin)
	27	You will see the following picture because you are an administrator:
	28	image:picture.jpg
	29	#end
34.2	30	{{/velocity}}
32.1	31	{{/code}}
1.1	32
	33	Will output:
36.1	34	{{image reference="sample1.png"/}}
1.1	35
36.1	36	=== ===
	37
1.1	38	* With XWiki and Velocity, you can retrieve informations contained in other pages
	39
32.2	40	{{code language="velocity"}}
1.1	41	#set($docRef = $services.model.createDocumentReference('', 'OtherSpace', 'OtherPage'))
	42	#set($document = $xwiki.getDocument($docRef))
	43	The content of the other document is:
	44	$document.getContent()
32.2	45	{{/code}}
1.1	46
	47
33.1	48	{{image reference="serrure.jpg"/}}
1.1	49
36.1	50	=== ===
1.1	51
	52	* or do advanced searches throught the wiki (via the //Query Module//) :
	53	** //« give me all the blog entries posted during the month of july 2012 and that are not archived and that have at least 3 comments and... »//
	54
33.1	55	{{image reference="detective.jpg"/}}
1.1	56
	57	=== ===
36.1	58
1.1	59	* But XWiki also allows you to use Velocity to save things in the wiki.
	60
32.2	61	{{code language="velocity"}}
1.1	62	#set($object = $doc.getObject('XWiki.XWikiUsers'))
	63	$object.set('first_name', 'Nobody')
	64	$doc.save()
32.2	65	{{/code}}
1.1	66
	67
33.1	68	{{image reference="nobody.jpg"/}}
1.1	69
	70	== Principles ==
	71
	72	=== Lines ===
36.1	73
1.1	74	* A line begining by '#' is a Velocity instruction
	75	* All other lines are normal lines
	76
32.2	77	{{code language="velocity"}}
1.1	78	## This is a velocity comment - a comment is never displayed and is used to
	79	## add useful information inside a source code.
	80	#set($myVar = 42)
	81	## The line above was a velocity instruction
	82	This line is a normal line
32.2	83	{{/code}}
1.1	84
	85	=== Variables ===
36.1	86
1.1	87	* A //variable// is like a box that can contains data: text, numbers, objects, etc...
	88	* A variable is always prefixed by a dollar '$'.
	89	* To create a variable, just use the //#set()// Velocity instruction
	90
32.2	91	{{code language="velocity"}}
1.1	92	#set($myVar = 42)
32.2	93	{{/code}}
1.1	94
	95	* If a variable is inside a normal line, the content of the variable will be displayed:
	96
32.2	97	{{code language="velocity"}}
1.1	98	#set($myVar = 42)
	99	I am $myVar years old.
32.2	100	{{/code}}
1.1	101
	102	will display:
	103
33.1	104	{{image reference="variables.png"/}}
1.1	105
36.1	106	=== ===
	107
1.1	108	Some variables are already created by XWiki when you write a Velocity code, and you can use them.
	109
	110
	111	This is some of them:
36.1	112
1.1	113	* //$hasEdit// : this variable tells us if the current user has the edit rights on the current page
	114	* //$isGuest// : this variable tells us if the current user is a guest
	115	* //$doc// : this variable represents the current document.
	116	* //$xwiki// : this special variable is a tool to perform complicated stuffs
	117	* //$request// : gives a lot of informations about the current request (like the referer, the query string, etc...)
	118
	119	=== Methods ===
36.1	120
1.1	121	* Some variable are //objects//. An object can contains //variables// and //methods//.
	122	* A method is like an //action// that the object can perform.
	123	* Some actions give you an information, some just perform something.
	124	* To call them, you write //$someObject.someMethod()// - with the '()'.
	125
	126	Examples:
	127
32.2	128	{{code language="velocity"}}
1.1	129	## will save the current document:
	130	$doc.save()
	131	## will give you the content of the document:
	132	$doc.getContent()
	133	## this method takes a "parameter", a text, which will be the new title:
	134	$doc.setTitle("My new title")
	135	## will give you the current skin
	136	$xwiki.getSkin()
32.2	137	{{/code}}
1.1	138
	139	=== Class ===
	140
	141	* Every object is different, they don't have the same variables and methods.
	142	* But every object is an //instance// of a //class//.
	143	* A //class// is like a model that describes what the object will have.
	144	** For example, the //Document// class has a //save// method, so every objects that are //instances// of //Document// will have the //save// method.
	145	** The //String// class has a //length// variable, so every instances of //String// will have this variable too.
	146
36.1	147	=== ===
	148
1.1	149	* You can use the following code to know what is the class of an object:
	150
32.2	151	{{code language="velocity"}}
1.1	152	#set($myVar = 42)
	153	$myVar.class.name ## will display 'java.lang.Integer'
	154	#set($myVar2 = "This is a text")
	155	$myVar2.class.name ## will display 'java.lang.String'
	156	$doc.class.name ## will display 'com.xpn.xwiki.api.Document'
	157	$xwiki.class.name ## will display 'com.xpn.xwiki.api.XWiki'
32.2	158	{{/code}}
1.1	159
	160
33.1	161	{{image reference="class.jpg"/}}
1.1	162
36.1	163	=== ===
	164
1.1	165	* Now that you know the class of your object, you can google it to have its documentation!
	166	* With this documentation, you will be able to knows what method you can use.
	167	** Example with //java.lang.String//
	168
33.1	169	{{image reference="javadoc.png"/}}
1.1	170
36.1	171	=== ===
	172
1.1	173	* As you may have notice, the classes come from the //Java// world.
	174	* The documentation about the java classes is called //Javadoc//.
	175	* So you can use the the //Javadoc// for Velocity too!
	176
33.1	177	{{image reference="java.jpg"/}}
1.1	178
	179	== Basic instructions ==
36.1	180
1.1	181	=== Conditions ===
36.1	182
1.1	183	* When you want to display something only under certain circounstances, you can use the //#if// command.
	184
32.2	185	{{code language="velocity"}}
1.1	186	#if($isGuest)
	187	Welcome visitor! You should subscribe to the wiki !
	188	#end
32.2	189	{{/code}}
1.1	190
	191	* You can also use the //#else// command:
	192
32.2	193	{{code language="velocity"}}
1.1	194	#if($isGuest)
	195	Welcome visitor! You should subscribe to the wiki !
	196	#else
	197	Hello $xcontext.user! I'm happy to see a registred user, I hate visitors!
	198	#end
32.2	199	{{/code}}
1.1	200
	201
33.1	202	{{image reference="visitors.jpg"/}}
1.1	203
	204	=== Conditions (bis) ===
36.1	205
1.1	206	* You can compare variables, with the following operators:
	207	//==//** : compare if the variables are equals
	208	//!=//** : say if the variables are differents
	209	//>//** : say if the variable is superior to the other
	210	//<//** : do the oposite
	211	//>=//** : say if the variable is superior or equal to the other
	212	//<=//** : say if the variable is inferior or equal to the other
	213
	214	* You can create complicated conditions, with the logic operators:
	215	//&&// : which means "AND"**.
	216	//\|\|// : which means "OR"**.
	217	//!// : which means "NOT"**.
	218
	219	=== Examples ===
36.1	220
32.2	221	{{code language="velocity"}}
1.1	222	#set($a = 12)
	223	#set($b = 28)
	224
	225	#if($a < $b)
	226	A is inferior
	227	#else
	228	B is inferior
	229	#end
	230
	231	#if($a < 20 && $b > 17)
	232	A is inferior than 20 AND B is superior than 17
	233	#end
	234
	235	#if($a == 15 \|\| $b <= 2)
	236	A equals 15 OR B is inferior than 2 or equal
	237	#end
32.2	238	{{/code}}
1.1	239
	240	=== Examples (bis) ===
36.1	241
32.2	242	{{code language="velocity"}}
1.1	243	#set($c = true)
	244
	245	#if($c)
	246	C is true
	247	#end
	248
	249	#if($doc.isNew())
	250	The document is New
	251	#else
	252	The document is an old document
	253	#end
	254
	255	#if(!$doc.isHidden())
	256	The document is NOT hidden
	257	#end
32.2	258	{{/code}}
1.1	259
	260	=== Lists ===
36.1	261
1.1	262	* You can create a list of objects.
	263
32.2	264	{{code language="velocity"}}
1.1	265	#set($myList = ['My first Item', 'My Second Item', 'My third item'])
32.2	266	{{/code}}
1.1	267
	268	* You can add a new element in the list:
	269
32.2	270	{{code language="velocity"}}
1.1	271	$myList.add('My fourth item')
32.2	272	{{/code}}
1.1	273
	274	* You can know how many objects are inside the list:
	275
32.2	276	{{code language="velocity"}}
1.1	277	$myList.size()
32.2	278	{{/code}}
1.1	279
	280	* You can ask if an object is inside the list
	281
32.2	282	{{code language="velocity"}}
1.1	283	$myList.contains('My Second Item') ## which tells me 'true' or 'false'
32.2	284	{{/code}}
1.1	285
	286	=== Example of lists ===
36.1	287
32.2	288	{{code language="velocity"}}
1.1	289	$doc.getComments() ## will give all the comments of the current page !
	290	$doc.getAttachmentList() ## will give all the attachments of the current page
	291	$xwiki.getSpaces() ## will give the list of the different spaces of the wiki
32.2	292	{{/code}}
1.1	293
	294
	295	How could I know the number of spaces in the wiki?
	296
32.2	297	{{code language="velocity"}}
1.1	298	...
32.2	299	{{/code}}
1.1	300
	301
	302	How could I know if the space 'BlaBla' exists?
	303
32.2	304	{{code language="velocity"}}
1.1	305	...
32.2	306	{{/code}}
1.1	307
	308
33.1	309	{{image reference="teacher.jpg"/}}
1.1	310
	311	=== Example of lists ===
36.1	312
32.2	313	{{code language="velocity"}}
1.1	314	$doc.getComments() ## will give all the comments of the current page !
	315	$doc.getAttachmentList() ## will give all the attachments of the current page
	316	$xwiki.getSpaces() ## will give the list of the different spaces of the wiki
32.2	317	{{/code}}
1.1	318
	319
	320	How could I know the number of spaces in the wiki?
	321
32.2	322	{{code language="velocity"}}
1.1	323	$xwiki.getSpaces().size()
32.2	324	{{/code}}
1.1	325
	326
	327	How could I know if the space 'BlaBla' exists?
	328
32.2	329	{{code language="velocity"}}
1.1	330	$xwiki.getSpaces().contains('BlaBla')
32.2	331	{{/code}}
1.1	332
	333
33.1	334	{{image reference="goodmark.jpg"/}}
1.1	335
	336	=== Foreach ===
36.1	337
1.1	338	* How can I display all the elements of a list in a nice way?
	339	** Use the //#foreach// loop, son.
	340	* Example:
	341
32.2	342	{{code language="velocity"}}
1.1	343	This is the list of all the spaces of the wiki
	344	#set($spaceList = $xwiki.getSpaces())
	345	#foreach($space in $spaceList)
	346	* $space
	347	#end
32.2	348	{{/code}}
1.1	349
	350	* Results:
33.1	351	{{image reference="foreach1.png"/}}
1.1	352
	353	== The API ==
	354
36.1	355	=== ===
	356
1.1	357	* XWiki offers a lot of objects with a lot of methods, to perform a lot of things !
	358	** Delete a document, add a tag to an other document, display the list of all blog entries, handle complex formulars, etc...
	359	* This objets & methods are called the API (as //Application Programming Interface//).
	360	* But how can I know what are theses objects and how to use it?
	361
33.1	362	{{image reference="API.jpg"/}}
1.1	363
	364	=== By using the XWiki Script Reference Documentation (SRD) ===
	365
33.1	366	{{image reference="SRD.png"/}}
1.1	367
37.7	368	Go to the [[SRD>>xwiki:ScriptingDocumentation.WebHome]].
1.1	369
	370	=== SRD ===
36.1	371
1.1	372	* The left column lists all the XWiki special variables that make the API.
	373	* Select one of them, and you will have all the methods this special variable offers
	374	** Examples:
	375	*** //$xwiki// offers a method //getDocument()//
	376	*** //$doc// has a method //addAttachment()//
	377	*** etc...
	378
36.1	379	=== Is the API a mess? ===
	380
1.1	381	* While looking at the SRD, we can ask youself //"how many special variables is there?"//
	382	* When we create a variable for our own usage, we have to be sure first to not call it as an existing special variable.
	383	** It's a mess!!!
	384
33.1	385	{{image reference="mess.jpg"/}}
1.1	386
	387	=== Introducing Script Services ===
36.1	388
1.1	389	* In order to make the things cleaner, the plan is to remove a lot of this special variables and replace them by //script services//.
	390	* Script services will become the only API in future.
	391	* All script services are prefixed by //$services//.
	392
33.1	393	{{image reference="datacenter.jpg"/}}
1.1	394
36.1	395	=== ===
	396
1.1	397	* To use a script service, you do it this way:
	398
32.2	399	{{code language="velocity"}}
1.1	400	$services.query ## to perform complicated researchs
	401	$services.localization ## to take care of the languages
	402	$services.officeimporter ## to import office documents
	403	...
32.2	404	{{/code}}
1.1	405
	406	* Of course, it is documented on the SRD!
	407
33.1	408	{{image reference="wayne.jpg"/}}
1.1	409
36.1	410	=== ===
	411
1.1	412	* Sometime, you have different ways to do the same thing:
	413	** Using an old method (which may be declared as //deprecated//).
	414	** Using a script service instead
	415	* Always perfers to use Script Service instead of deprecated APIs!!!
	416
32.2	417	{{code language="velocity"}}
1.1	418	$xwiki.searchDocument() ## allow us to perfom a query with the HQL language
	419	## now please use:
	420	$services.query.hql() ## allow us to perfom a query with the HQL language
	421	## or even better:
	422	$services.query.xwql() ## XWQL language is easier to use
32.2	423	{{/code}}
1.1	424
	425	* Because it's the future!
	426
33.1	427	{{image reference="future.jpg"/}}
1.1	428
	429	== Manipulation of XObjects ==
36.1	430
1.1	431	=== What is an XObject ? ===
36.1	432
1.1	433	* An //XObject// is an object that you can save in the wiki.
	434	* An XObject is attached on a document, and you can see them with the "objects editor" on the wiki.
	435
33.1	436	{{image reference="edit_objects.png"/}}
1.1	437
36.1	438	=== ===
	439
33.1	440	{{image reference="objects.png"/}}
1.1	441
	442	=== XClass ===
36.1	443
1.1	444	* An //XClass// is a //class// (a //description//) for XObjects.
	445	** You can define them using the class editor.
	446	** Or by using //Application Within Minutes//!
	447
	448	=== Class Editor ===
36.1	449
33.1	450	{{image reference="class_editor.png"/}}
1.1	451
	452	=== Application Within Minutes ===
36.1	453
33.1	454	{{image reference="appwithinminutes.png"/}}
1.1	455
	456	=== Why using XClass and XObjects? ===
36.1	457
1.1	458	* It allows us to store structured informations.
	459	** A //Blog Post// (with a //title//, a //date//, a //content//, etc...)
	460	** An //Evaluation document// (with a //remark// for each //category//, a //mark//, etc...)
	461	** An //Holiday Request// (with //dates//, //status//, etc...)
	462
	463	* So the //information// is not lost in a giant document that holds only a big text...
	464	** And you can create //Applications//!
	465
	466	=== XClass is used //everywhere// ===
36.1	467
1.1	468	* Almost everything in XWiki is an XClass and stored as XObjects!
	469	** //Users//
	470	** //Groups//
	471	** //Comments//
	472	** //Tags//
	473	** //Access Rights//
	474	** ....
	475	* Learn to use //XClass// and you can control all your wiki.
	476
	477	=== A comment is an XObject ===
36.1	478
33.1	479	{{image reference="comments.png"/}}
1.1	480
	481	=== A user is an XObject ===
36.1	482
33.1	483	{{image reference="user.png"/}}
1.1	484
	485	=== How to get an XObject with Velocity? ===
	486
32.2	487	{{code language="velocity"}}
1.1	488	## First, get the object
	489	#set($object = $doc.getObject('XWiki.XWikiUsers'))
	490	## The parameter is the name of the class of the object you want to have
	491	## (a document can hold multiple objects of different classes)
	492	## The class name is the Document name where the class is defined
	493
	494	## Display a parameter:
	495	$object.display('first_name', 'view')
	496	## the parameter is the name of the field you want to display
	497	## if you are in "edit" mode, an HTML field will be displayed instead of the object value.
	498
	499	## Set values:
	500	$object.set('last_name', 'Bond')
	501	$object.set('first_name', 'James')
	502
	503	## Then save the document if you want your changes to be conserved
	504	## (you can add a comment when you save)
	505	$doc.save('I have changed the name of the user.')
32.2	506	{{/code}}
1.1	507
	508	=== You can rollback what your script have done ===
36.1	509
33.1	510	{{image reference="rollback.png"/}}
1.1	511
	512	== Tips ==
	513
	514	=== How to get an other document? ===
36.1	515
1.1	516	* In the past, we used to do:
	517
32.2	518	{{code language="velocity"}}
1.1	519	#set($document = $xwiki.getDocument('Space.Page'))
32.2	520	{{/code}}
1.1	521
	522	* But it's not good, because what if the page name has a dot?
	523
32.2	524	{{code language="velocity"}}
1.1	525	#set($document = $xwiki.getDocument('Space.Pa.ge'))
	526	## ??? What is the Space ? What is the Page ?
32.2	527	{{/code}}
1.1	528
	529	* And what will happen if the document name have accents or weird characters?
	530
36.1	531	=== Solution: use references ! ===
1.1	532
32.2	533	{{code language="velocity"}}
1.1	534	#set($reference = $services.model.createDocumentReference('Wiki', 'Space', 'Page'))
	535	#set($document = $xwiki.getDocument($reference))
32.2	536	{{/code}}
1.1	537
35.1	538	* It is better! The reference tool allow us to strictly separe what is the space and what is the page
1.1	539	* And the reference tool will take care of weird characters !
	540
32.2	541	{{code language="velocity"}}
1.1	542	#set($reference = $services.model.createDocumentReference('Wiki', 'Space', 'Pa.ge'))
	543	#set($document = $xwiki.getDocument($reference))
	544	## Not a problem!!!
32.2	545	{{/code}}
1.1	546
	547	=== References ===
36.1	548
1.1	549	* You can get create references for documents in other wikis :
	550
32.2	551	{{code language="velocity"}}
1.1	552	#set($reference = $services.model.createDocumentReference('Wiki', 'Space', 'Page'))
32.2	553	{{/code}}
1.1	554
	555	* If you want to get a document in the current wiki, you can set an empty parameter:
	556
32.2	557	{{code language="velocity"}}
1.1	558	#set($reference = $services.model.createDocumentReference('', 'Space', 'Page'))
	559	## the reference point a document in the current wiki
32.2	560	{{/code}}
1.1	561
27.2	562	=== Use case: changing the name of a user ===
1.1	563
32.2	564	{{code language="velocity"}}
1.1	565	## First, create a reference to his user page
	566	#set($reference = $services.model.createDocumentReference('', 'XWiki', 'ldubost'))
	567	## Then, get its document
	568	#set($document = $xwiki.getDocument($reference))
	569	## Then, get the 'User' object
	570	#set($object = $document.getObject('XWiki.XWikiUsers'))
	571	## Then change his name
	572	$object.set('first_name', 'Harry')
	573	$object.set('last_name', 'Potter')
	574	## And save the document
	575	$document.save()
32.2	576	{{/code}}
1.1	577
27.2	578	=== But remember we know who changes what! ===
36.1	579
33.1	580	{{image reference="history.png"/}}
1.1	581
	582	(% style="text-align: right; margin-top: 20px;" %)
	583	"//I have your name and I know where you live...//"
	584
	585	== Going further ==
36.1	586
	587	=== ===
	588
1.1	589	* See the [[Velocity documentation>>http://velocity.apache.org/]] to have more details about the language itself
37.1	590	* See the [[XWiki Script Guide>>doc:Documentation.DevGuide.Scripting.WebHome]] to have some informations about how to make scripts in XWiki
36.3	591	* See the [[XWiki Query Module>>doc:extensions:Extension.Query Module]] to learn how to do advanced queries
36.4	592	* See the [[XWiki Data Model>>doc:Documentation.DevGuide.DataModel]] to learn how to create your XWiki classes
1.1	593
	594	But in general:
36.1	595
1.1	596	* practice and ask for help!!!
	597
36.1	598	=== ===
	599
1.1	600	* I hope you now have a better idea of what Velocity is and how you can use it in XWiki.
	601
33.1	602	{{image reference="velocity.jpg"/}}

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