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Wiki source code of Your First Rest Project

Version 21.1 by Filippo Laurìa on 2013/07/22 12:25
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1
2
3 {{toc/}}
4
5 = Introduction =
6
7 In the first part of the Blog tutorial, you will learn:
8
9 * How to create a EOModel for the database (we will use H2)
10 * How to use migrations to create the database tables
11 * How to use ERRest to create blog posts with JSON format and how to display the blog posts in HTML for readers
12
13 = Create a new project =
14
15 You will need to create a new project for this tutorial. In Eclipse, open the **File** menu, select **New** and select **Wonder REST Application**. Name your project as //BlogRest//.
16
17 = Create the database model =
18
19 == Database structure ==
20
21 We will build a small database model for the blog. The database will have two tables: BlogEntry and Author.
22
23 BlogEntry will have the following columns:
24
25 |=(((
26 Column name
27 )))|=(((
28 Type
29 )))|=(((
30 Constraints
31 )))
32 |(((
33 id
34 )))|(((
35 integer
36 )))|(((
37 primary key
38 )))
39 |(((
40 title
41 )))|(((
42 string(255)
43 )))|(((
44
45 )))
46 |(((
47 content
48 )))|(((
49 string(4000)
50 )))|(((
51
52 )))
53 |(((
54 creationDate
55 )))|(((
56 timestamp
57 )))|(((
58
59 )))
60 |(((
61 lastModified
62 )))|(((
63 timestamp
64 )))|(((
65
66 )))
67 |(((
68 author
69 )))|(((
70 integer
71 )))|(((
72 relation with Author
73 )))
74
75 Author will have the following columns:
76
77 |=(((
78 Column name
79 )))|=(((
80 Type
81 )))|=(((
82 Constraints
83 )))
84 |(((
85 id
86 )))|(((
87 integer
88 )))|(((
89 primary key
90 )))
91 |(((
92 firstName
93 )))|(((
94 string(50)
95 )))|(((
96
97 )))
98 |(((
99 lastName
100 )))|(((
101 string(50)
102 )))|(((
103
104 )))
105 |(((
106 email
107 )))|(((
108 string(100)
109 )))|(((
110 unique
111 )))
112
113 == Creating the EOModel ==
114
115 To create the database, we will first create a EOModel and use migrations to build the database on the file system (H2 will take care of creating the database file).
116
117 An EOModel consists of entities, attributes and relationships. When using it in a RDBMS context, an entity is a table (or a view), an attribute is a table column and a relationship is a join between two tables.
118
119 To create the EOModel, in the project right-click on the project name and select **New** -> **EOModel**.
120
121 Name it **BlogModel** and in the plugin list, select **H2**. Click **Finish**.
122
123 The model should show up in a window that looks like this:
124
125 [[image:attach:EOModeler.png]]
126
127 If it didn't show up, the window might have opened behind the main Eclipse window. If that's the case, open the **Window** menu and select the windows that have //Entity Modeler// in its name.
128
129 In the Entity Modeler window, click on **Default**, and for the **URL** field, type
130
131 {{code}}
132 jdbc:h2:~/BlogTutorial
133 {{/code}}
134
135 . When the database will be created, it will be stored in your home directory (/Users/youruser/ on OS X).
136
137 Now, right-click on **BlogModel** and select **New Entity**.
138
139 Type the following details in the **Basic** tab:
140
141 * **Name**: BlogEntry
142 * **Table Name**: BlogEntry
143 * **Class Name**: your.app.model.BlogEntry
144
145 Now, it's time to add the entity's attributes (aka, the table's columns). You will see that the entity already have an attributed named "id". That attribute is a integer for the primary key. Leave it there.
146
147 Let's create the first attribute: the title of the blog entry. Right-click on the entity and select **New Attribute**. Type the following values:
148
149 * **Name**: title
150 * **Column**: title
151 * **Prototype**: varchar255
152
153 When you use prototypes, you don't need to define the type (varchar, int, etc.) for the database, so by using prototypes, if you switch from a RDBMS system to another one, say from H2 to MySQL, you only need to change the JDBC connection string and bundle the EOF plugin for the RDBMS, no need to switch data types in the model.
154
155 Now, repeat the last two steps to create the other attributes for the **BlogEntry** entity, with the following values:
156
157 |=(((
158 Attribute name
159 )))|=(((
160 Column
161 )))|=(((
162 Prototype
163 )))
164 |(((
165 content
166 )))|(((
167 content
168 )))|(((
169 longtext
170 )))
171 |(((
172 creationDate
173 )))|(((
174 creationDate
175 )))|(((
176 dateTime
177 )))
178 |(((
179 lastModified
180 )))|(((
181 lastModified
182 )))|(((
183 dateTime
184 )))
185
186 If you did everything well, the list of attributes should look like this:
187
188 You will notice that the attributes have a column with a lock in it. When a lock is present, it will use the value of that attribute for //UPDATE ... WHERE attribute = ''// statement. This is to do optimistic locking, aka to prevent data conflict when the data object was modified by two different users. Using timestamps for optimistic locking is not a good idea because for certain RDBMS, the value can be different because of milliseconds, so remove the locks on the **creationDate** attribute. The final list should look like this:
189
190 Next step is to create the **Author** entity. Create a new entity with **Author** at its name (and also as the table name), and for the class name, use **your.app.model.Author**. The attributes for this entity are:
191
192 |=(((
193 Attribute name
194 )))|=(((
195 Column
196 )))|=(((
197 Prototype
198 )))
199 |(((
200 firstName
201 )))|(((
202 firstName
203 )))|(((
204 varchar50
205 )))
206 |(((
207 lastName
208 )))|(((
209 lastName
210 )))|(((
211 varchar50
212 )))
213 |(((
214 email
215 )))|(((
216 email
217 )))|(((
218 varchar100
219 )))
220
221 Final list of attributes should look like this:
222
223 Now, it's time to link the two entities together. An Author can have multiple blog entries, and a BlogEntry can only have one author. To create the relationship (the join), right-click on **Author** and select **New Relationship**. On your right, select **BlogEntry** in the list. On your left, select **to many BlogEntries**, and on your right, select **to one Author**. Now, in BlogEntry, we need to store the primary key of the author so that we can make the join. The relationship builder allow us to add that attribute, so make sure **and a new foreign key named** is checked (it is checked by default). The **Create Relationship** pane should look like this:
224
225 If you check in the **Outline** tab, you should see that **Author** now have a **blogEntries** relationship, and **BlogEntry** have a **author** relationship.
226
227 You are now ready to save the model. Save it (File -> Save) and close the **Entity Modeler** window. If you open the **Sources** in the main Eclipse window, you will notice that the **Sources** folder contains a package named **your.app.model**. (If this folder doesn't appear, you may need to set your preferences to automatically generate these source files; see the second suggestion on [[http:~~/~~/wiki.wocommunity.org/display/documentation/Useful+Eclipse+or+WOLips+Preferences>>url:http://wiki.wocommunity.org/display/documentation/Useful+Eclipse+or+WOLips+Preferences||rel="nofollow" shape="rect" class="external-link"]].)
228
229 That package have four Java classes: **_Author**, **Author**, **_BlogEntry** and **BlogEntry**. Those classes were generated by Veogen, a templating engine build on Velocity. The two classes that starts with a underscore are recreated every time you change the EOModel, so if you want to change something in those classes, you need to change the template (no need for that right now). But you can change freely the two classes that don't have the underscore, and this is what we will be doing.
230
231 What we are going to do is to write a simple method that returns the full name of an author, e.g. a method that simply concatenate the first name, a space and the last name of the author. To do so, double-click on **Author.java** and add the following methods:
232
233 {{code}}
234 public String fullName() {
235 return this.firstName() + " " + this.lastName();
236 }
237
238 {{/code}}
239
240 Nothing fancy here. Now open **BlogEntry.java** and add the following method:
241
242 {{code}}
243 @Override
244 public void awakeFromInsertion(EOEditingContext editingContext) {
245 super.awakeFromInsertion(editingContext);
246 NSTimestamp now = new NSTimestamp();
247 setCreationDate(now);
248 setLastModified(now);
249 }
250
251 {{/code}}
252
253 Why are we adding this? **awakeFromInsertion** is a very good way of setting default values when creating a new instance of a Enterprise Object (EO). In this case, we want to set automatically the creation and last modification dates without having the user to add those values.
254
255 Now, let's use migrations to actually create the database.
256
257 == Using migrations ==
258
259 Migrations allow you to create the tables and columns (and some types of constraint). **Entity Modeler** has support to generate the code for the first migration, which is called "migration 0". To do that, open the EOModel (**BlogModel EOModel** in the **Resources** folder), right-click on the model name and select **Generate Migration**.
260
261 Copy the generated code in the clipboard. Close **Entity Modeler** and in the main Eclipse window, right-click on **Sources**, select **New** and select **Class**.
262
263 Type **your.app.model.migrations** as the package and **BlogModel0** as the name of the class. Click **Finish**.
264
265 In the **Sources** folder, open the **your.app.model.migrations** package, a class named **BlogModel0** should be there. Delete everything in that file **EXCEPT** the first line (which should be //package your.app.model.migrations//) and paste the code that was generated by **Entity Modeler**. Save the file.
266
267 One last step: migrations are disabled by default. To enable them, you need to uncomment two properties in the **Properties** file that is located in the **Resources** folder. Open that file (double-click on it).
268
269 Remove the pound char in front of those two properties:
270
271 {{code}}
272 #er.migration.migrateAtStartup=true
273 #er.migration.createTablesIfNecessary=true
274
275 {{/code}}
276
277 After removing the pound char, the two properties should look like this:
278
279 {{code}}
280 er.migration.migrateAtStartup=true
281 er.migration.createTablesIfNecessary=true
282
283 {{/code}}
284
285 You are now ready to start the application so that it creates the database! To do so, right-click on **Application.java** (in the **your.app** folder) and select **Run As** -> **WOApplication**. In Eclipse's Console tab, you should see some output, including something similar to:
286
287 {{code}}
288 BlogRest[62990] INFO er.extensions.migration.ERXMigrator - Upgrading BlogModel to version 0 with migration 'your.app.model.migrations.BlogModel0@4743bf3d'
289 BlogRest[62990] INFO er.extensions.jdbc.ERXJDBCUtilities - Executing CREATE TABLE Author(email VARCHAR(100) NOT NULL, firstName VARCHAR(50) NOT NULL, id INTEGER NOT NULL, lastName VARCHAR(50) NOT NULL)
290 BlogRest[62990] INFO er.extensions.jdbc.ERXJDBCUtilities - Executing ALTER TABLE Author ADD PRIMARY KEY (id)
291 BlogRest[62990] INFO er.extensions.jdbc.ERXJDBCUtilities - Executing CREATE TABLE BlogEntry(authorID INTEGER NOT NULL, content TIMESTAMP NOT NULL, creationDate TIMESTAMP NOT NULL, id INTEGER NOT NULL, title VARCHAR(255) NOT NULL)
292 BlogRest[62990] INFO er.extensions.jdbc.ERXJDBCUtilities - Executing ALTER TABLE BlogEntry ADD PRIMARY KEY (id)
293 BlogRest[62990] INFO er.extensions.jdbc.ERXJDBCUtilities - Executing ALTER TABLE BlogEntry ADD CONSTRAINT "FOREIGN_KEY_BLOGENTRY_AUTHORID_AUTHOR_ID" FOREIGN KEY (authorID) REFERENCES Author (id)
294 BlogRest[62990] DEBUG NSLog - evaluateExpression: <er.h2.jdbcadaptor.ERH2PlugIn$H2Expression: "UPDATE _dbupdater SET version = ? WHERE modelname = ?" withBindings: 1:0(version), 2:"BlogModel"(modelName)>
295
296 {{/code}}
297
298 If you see this and that the application is running (it should open a window in your favorite browser), migration worked and your database have been created, congratulations! You can now stop the application (click the square red button in Eclipse's Console tab) and continue to the next step.
299
300 = Creating REST controllers and routes =
301
302 Project Wonder contains a framework called ERRest, which follow the same patterns as Ruby on Rails REST concepts. Using REST-style URLs is perfect for building a public blog and to create REST services to manage posting over HTTP with JSON, XML or other formats.
303
304 By default, a REST route in ERRest will generate a link like this:
305
306 {{code}}
307 /cgi-bin/WebObjects/AppName.woa/ra/EntityName/id
308 {{/code}}
309
310 So for our case, to get the first blog posting from BlogRest, the URL will look like this:
311
312 {{code}}
313 /cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries/1.html
314 {{/code}}
315
316 {{info}}
317 You can shorten the URL by using mod_rewrite in Apache httpd
318 {{/info}}
319
320 == Creating controllers ==
321
322 ERRest needs controllers to act as a broker between working with the objects and the routes. So let's create a controller for BlogEntry.
323
324 Create a Java class named **BlogEntryController**, in the **your.app.rest.controllers** package, that will extend from **er.rest.routes.ERXDefaultRouteController**. Click **Finish**.
325
326 When you extend from **ERXDefaultRouteController**, a bunch of methods are added to the subclass. Let's see what they are for.
327
328 * **updateAction**: to update a specific instance of BlogEntry
329 * **destroyAction**: to delete a specific instance of BlogEntry
330 * **showAction**: to get one specific instance of BlogEntry
331 * **createAction**: to create a new object (a new instance of BlogEntry)
332 * **indexAction**: to list all (or a sublist) of the objects.
333
334 {{info}}
335 In Project Wonder, **Action** at the end of a method is a convention for REST and Direct Actions, when you call those methods from certain components, you don't need to add the **Action** part.
336 {{/info}}
337
338 For this tutorial, we will implement the **createAction** and **indexAction** methods. But first, we need to create a key filter. A key filter will... filter the input and the output of REST request so that you don't have to send all attributes for a blog entry. For example, we want to show the details for an author, but we don't want to show the password for the author (in real-life, the password would be encrypted)!
339
340 Add this method in **BlogEntryController**:
341
342 {{code}}
343 protected ERXKeyFilter filter() {
344 ERXKeyFilter personFilter = ERXKeyFilter.filterWithAttributes();
345 personFilter.setAnonymousUpdateEnabled(true);
346
347 ERXKeyFilter filter = ERXKeyFilter.filterWithAttributes();
348 filter.include(BlogEntry.AUTHOR, personFilter);
349 filter.setUnknownKeyIgnored(true);
350
351 return filter;
352 }
353
354 {{/code}}
355
356 Now, let's implement the **createAction** method:
357
358 {{code}}
359 public WOActionResults createAction() throws Throwable {
360 BlogEntry entry = create(filter());
361 editingContext().saveChanges();
362 return response(entry, filter());
363 }
364
365 {{/code}}
366
367 In 3 lines of code, you can create an object based on the request, save the new object to the database and return the new object in the response. Not bad, eh?
368
369 Last step in the controller: implementing the **indexAction** method. Again, the code is simple:
370
371 {{code}}
372 public WOActionResults indexAction() throws Throwable {
373 NSArray<BlogEntry> entries = BlogEntry.fetchAllBlogEntries(editingContext());
374 return response(entries, filter());
375 }
376
377 {{/code}}
378
379 That code simply fetch all blog entries and return them in the response.
380
381 We can now go to the next step: adding the routes.
382
383 == Adding the routes ==
384
385 A route in ERRest is simply a way to define the URL for the entities and to specify which controller the route should use. When your controller extends from **ERXDefaultRouteController**, it's easy to register a controller and a route. In **Application.java**, in the **Application** constructor, add the following code:
386
387 {{code}}
388 ERXRouteRequestHandler restRequestHandler = new ERXRouteRequestHandler();
389 restRequestHandler.addDefaultRoutes(BlogEntry.ENTITY_NAME);
390 ERXRouteRequestHandler.register(restRequestHandler);
391 setDefaultRequestHandler(restRequestHandler);
392
393 {{/code}}
394
395 The **addDefaultRoutes** method do all of the required magic, and use convention. That's why we had to name the controller **BlogEntryController**, because the convention is <EntityName>Controller.
396
397 We are now reading to add and list blog postings! Start the application and take notice of the URL. It should be something like _[[http:~~/~~/yourip:someport/cgi-bin/WebObjects/BlogRest.woa_>>url:http://youripsomeport||shape="rect"]]
398
399 == Adding posts and authors with curl ==
400
401 Since we didn't implement any HTML for our REST routes, we will create blog entries with //curl//, an open source HTTP client that is bundled with Mac OS X (you can use another client, like wget, if you like too). So let's create a blog entry.
402
403 To create a blog entry, you need to use the POST HTTP method. We will use JSON as the format since it's a bit less chatty than XML. So if the URL to the application is //[[http:~~/~~/192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa_>>url:http://192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa_||shape="rect"]], the full _curl// command will be:
404
405 {{code}}
406 curl -X POST -v -d '{ "title": "First post", "content": "Some text", "author": { "firstName": "Pascal", "lastName": "Robert", "email": "probert@macti.ca" } }' http://192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries.json
407 {{/code}}
408
409 The response should look this:
410
411 {{code}}
412 HTTP/1.0 201 Apple WebObjects
413 Content-Length: 249
414 x-webobjects-loadaverage: 0
415 Content-Type: application/json
416
417 {"id":1,"type":"BlogEntry","content":"Some text","creationDate":"2011-12-27T21:59:08Z","title":"First post","author":{"id":1,"type":"Author","email":"probert@macti.ca","firstName":"Pascal","lastName":"Robert"}}
418
419 {{/code}}
420
421 To get a list of blog entries:
422
423 {{code}}
424 curl -X GET http://192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries.json
425
426 {{/code}}
427
428 You can stop the application and proceed to the next step.
429
430 == Adding HTML views for blog posts ==
431
432 Now, let's build a HTML view for blog posts (you don't want your readers to get your posts by JSON, right?). Again, we will use convention to make it work easily. Open up **BlogEntryController** and add the following method:
433
434 {{code}}
435 @Override
436 protected boolean isAutomaticHtmlRoutingEnabled() {
437 return true;
438 }
439
440 {{/code}}
441
442 Switching the return value of this method says that we will follow a certain convention for HTML components. The convention for automatic HTML routing is that the component should be named <EntityName><Action>Page.wo. So in our case, the component will be **BlogEntryIndexPage**. Right-click on the project name in Eclipse and select **New** -> **WOComponent**. Change the name to **BlogEntryIndexPage** and check the **Create HTML contents** button. Click **Finish**.
443
444 The next step to get it to work is to make **BlogEntryIndexPage** to implement the **er.rest.routes.IERXRouteComponent** interface.
445
446 {{code}}
447 import er.rest.routes.IERXRouteComponent;
448
449 public class BlogEntryIndexPage extends WOComponent implements IERXRouteComponent {
450
451 {{/code}}
452
453 So now, the automatic HTML routing will send the request for **ra/blogEntries.html** to the **BlogEntryIndexPage** component. But we don't have any content in this component, so let's make a method to fetch all blog entries per creation date in descending order. So in **BlogEntryIndexPage.java**, add the following method:
454
455 {{code}}
456 public NSArray<BlogEntry> entries() {
457 EOEditingContext ec = ERXEC.newEditingContext();
458 return BlogEntry.fetchAllBlogEntries(ec, BlogEntry.CREATION_DATE.descs());
459 }
460
461 {{/code}}
462
463 We need to use that method in a WORepetition, and for that loop, we need a BlogEntry variable to iterate in the list, so add the following code to **BlogEntryIndexPage.java**:
464
465 {{code}}
466 private BlogEntry entryItem;
467
468 public BlogEntry entryItem() {
469 return entryItem;
470 }
471
472 public void setEntryItem(BlogEntry entryItem) {
473 this.entryItem = entryItem;
474 }
475
476 {{/code}}
477
478 The Java part is done, so let's add the loop inside the component. Open **BlogEntryIndexPage.wo** (it's located in the **Component** folder) and right after the <body> tag, add:
479
480 {{code}}
481 <wo:loop list="$entries" item="$entryItem">
482 <p><wo:str value="$entryItem.title" /></p>
483 <p><wo:str value="$entryItem.author.fullName" /></p>
484 </wo:loop>
485
486 {{/code}}
487
488 That component code will loop over the blog entries and display the title of the entry + the name of the author. Save everything and run the application.
489
490 If you go to [[http:~~/~~/192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries.html>>url:http://192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries.html||shape="rect"]], you will see the list of blog entries!
491
492 Now that we have a list of blog entries, let's make a page to show the content of a blog entry. Create a new component named **BlogEntryShowPage**.
493
494 Open **BlogEntryShowPage.java** and make sure the class implements **er.rest.routes.IERXRouteComponent**.
495
496 {{code}}
497 import er.rest.routes.IERXRouteComponent;
498
499 public class BlogEntryShowPage extends WOComponent implements IERXRouteComponent {
500
501 {{/code}}
502
503 We need to add other methods to receive the BlogEntry object from the controller. In **BlogEntryShowPage.java**, add:
504
505 {{code}}
506 private BlogEntry blogEntry;
507
508 @ERXRouteParameter
509 public void setBlogEntry(BlogEntry blogEntryFromController) {
510 this.blogEntry = blogEntryFromController;
511 }
512
513 public BlogEntry blogEntry() {
514 return this.blogEntry;
515 }
516
517 {{/code}}
518
519 The **@ERXRouteParameter** annotation tells the REST framework that it can automatically receive an object from the controller. And again, it's convention at work. You have to use the annotation and the setter name should be //set<EntityName>//, so for a BlogEntry, it's //setBlogEntry//, for a Author, it will be //setAuthor//.
520
521 The Java part of the work is done, so save the Java class. It's time to work on the component part. Open **BlogEntryShowPage.wo** and between the <body></body> part, add:
522
523 {{code}}
524 <h1><wo:str value="$blogEntry.title" /></h1>
525 <p><wo:str value="$blogEntry.content" /></p>
526 <p>Created on: <wo:str value="$blogEntry.creationDate" dateformat="%Y/%m/%d" /></p>
527 <p>Added by: <wo:str value="$blogEntry.author.fullName" /></p>
528
529 {{/code}}
530
531 Our view component is done, the only thing remaining is a link for the blog entry list (BlogEntryIndexPage) to the view page (BlogEntryShowPage). Save **BlogEntryShowPage.wo** and open **BlogEntryIndexPage.wo**. We are going to add a link on the title, you will replace to replace this:
532
533 {{code}}
534 <p><wo:str value="$entryItem.title" /></p>
535
536 {{/code}}
537
538 with:
539
540 {{code}}
541 <p><wo:ERXRouteLink entityName="BlogEntry" record="$entryItem" action="show"><wo:str value="$entryItem.title" /></wo:ERXRouteLink></p>
542
543 {{/code}}
544
545 Save the component and run the app. Go to [[http:~~/~~/192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries.html>>url:http://192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries.html||shape="rect"]] to get the list of posts, and you should see a link on the title. Click on it, and now you get the full details of the blog entry!
546
547 The REST part of this tutorial is now complete, [[you can now move to the next part of the tutorial>>doc:Your First Framework]].