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Wiki source code of Your First Rest Project

Version 31.1 by Pascal Robert on 2011/12/27 23:07
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1 {{toc}}{{/toc}}
2
3 = Introduction =
4
5 In the first part of the Blog tutorial, you will learn:
6
7 * How to create a EOModel for the database (we will use H2)
8 * How to use migrations to create the database tables
9 * How to use ERRest to create blog posts with JSON format and how to display the blog posts in HTML for readers
10
11 = Create a new project =
12
13 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//.
14
15 = Create the database model =
16
17 == Database structure ==
18
19 We will build a small database model for the blog. The database will have two tables: BlogEntry and Author.
20
21 BlogEntry will have the following columns:
22
23 |= Column name |= Type |= Constraints
24 | id | integer | primary key
25 | title | string(255) |
26 | content | string(4000) |
27 | creationDate | timestamp |
28 | author | integer | relation with Author
29
30 Author will have the following columns:
31
32 |= Column name |= Type |= Constraints
33 | id | integer | primary key
34 | firstName | string(50) |
35 | lastName | string(50) |
36 | email | string(100) | unique
37
38 == Creating the EOModel ==
39
40 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).
41
42 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.
43
44 To create the EOModel, in the project right-click on the project name and select **New** > **EOModel**.
45
46 Name it **BlogModel** and in the plugin list, select **H2**. Click **Finish**.
47
48 The model should show up in a window that looks like this:
49
50 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.
51
52 In the Entity Modeler window, click on **Default**, and for the **URL** field, type {{code}}jdbc:h2:~/BlogTutorial{{/code}}. When the database will be created, it will be stored in your home directory (/Users/youruser/ on OS X).
53
54 Now, right-click on **BlogModel** and select **New Entity**.
55
56 Type the following details in the **Basic** tab:
57
58 * **Name**: BlogEntry
59 * **Table Name**: BlogEntry
60 * **Class Name**: your.app.model.BlogEntry
61
62 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.
63
64 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:
65
66 * **Name**: title
67 * **Column**: title
68 * **Prototype**: varchar255
69
70 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.
71
72 Now, repeat the last two steps to create the other attributes for the **BlogEntry** entity, with the following values:
73
74 |= Attribute name |= Column |= Prototype
75 | content | content | longtext
76 | creationDate | creationDate | dateTime
77
78 If you did everything well, the list of attributes should look like this:
79
80 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 **lastModified** and **creationDate** attributes. The final list should look like this:
81
82 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:
83
84 |= Attribute name |= Column |= Prototype
85 | firstName | firstName | varchar50
86 | lastName | lastName | varchar50
87 | email | email | varchar100
88
89 Final list of attributes should look like this:
90
91 Now, it's time to link the two entities together. A 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 left, 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:
92
93 If you check in the **Outline** tab, you should see that **Author** now have a **blogEntries** relationship, and **BlogEntry** have a **author** relationship.
94
95 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**.
96
97 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.
98
99 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:
100
101 {{code}}
102
103 public String fullName() {
104 return this.firstName() + " " + this.lastName();
105 }
106
107 {{/code}}
108
109 Nothing fancy here. Now open **BlogEntry.java** and add the following method:
110
111 {{code}}
112
113 @Override
114 public void awakeFromInsertion(EOEditingContext editingContext) {
115 super.awakeFromInsertion(editingContext);
116 this.setCreationDate(new NSTimestamp());
117 }
118
119 {{/code}}
120
121 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 date without having the user to add that value.
122
123 Now, let's use migrations to actually create the database.
124
125 == Using migrations ==
126
127 Migrations allow you to create the tables and columns (and some types of constraint). **Entity Modeler** have 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**.
128
129 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**.
130
131 Type **your.app.model.migrations** as the package and **BlogModel0** as the name of the class. Click **Finish**.
132
133 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.
134
135 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).
136
137 Remove the pound char in front of those two properties:
138
139 {{code}}
140
141 #er.migration.migrateAtStartup=true
142 #er.migration.createTablesIfNecessary=true
143
144 {{/code}}
145
146 After removing the pound char, the two properties should look like this:
147
148 {{code}}
149
150 er.migration.migrateAtStartup=true
151 er.migration.createTablesIfNecessary=true
152
153 {{/code}}
154
155 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:
156
157 {{code}}
158
159 BlogRest[62990] INFO er.extensions.migration.ERXMigrator - Upgrading BlogModel to version 0 with migration 'your.app.model.migrations.BlogModel0@4743bf3d'
160 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)
161 BlogRest[62990] INFO er.extensions.jdbc.ERXJDBCUtilities - Executing ALTER TABLE Author ADD PRIMARY KEY (id)
162 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)
163 BlogRest[62990] INFO er.extensions.jdbc.ERXJDBCUtilities - Executing ALTER TABLE BlogEntry ADD PRIMARY KEY (id)
164 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)
165 BlogRest[62990] DEBUG NSLog - evaluateExpression: <er.h2.jdbcadaptor.ERH2PlugIn$H2Expression: "UPDATE _dbupdater SET version = ? WHERE modelname = ?" withBindings: 1:0(version), 2:"BlogModel"(modelName)>
166
167 {{/code}}
168
169 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.
170
171 = Creating REST controllers and routes =
172
173 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.
174
175 By default, a REST route in ERRest will generate a link like this:
176
177 {{code}}
178 /cgi-bin/WebObjects/AppName.woa/ra/EntityName/id
179 {{/code}}
180
181 So for our case, to get the first blog posting from BlogRest, the URL will look like this:
182
183 {{code}}
184 /cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries/1.html
185 {{/code}}
186
187 {{info}}
188 You can shorten the URL by using mod_rewrite in Apache httpd
189 {{/info}}
190
191 == Creating controllers ==
192
193 ERRest needs controllers to act as a broker between working with the objects and the routes. So let's create a controller for BlogEntry.
194
195 Create a Java class named **BlogEntryController**, in the **your.app.rest.controllers** package, that will extend from **er.rest.routes.ERXDefaultRouteController**. Click **Finish**.
196
197 When you extend from **ERXDefaultRouteController**, a bunch of methods are added to the subclass. Let's see what they are for.
198
199 * **updateAction**: to update a specific instance of BlogEntry
200 * **destroyAction**: to delete a specific instance of BlogEntry
201 * **showAction**: to get one specific instance of BlogEntry
202 * **createAction**: to create a new object (a new instance of BlogEntry)
203 * **indexAction**: to list all (or a sublist) of the objects.
204
205 {{info}}
206 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.
207 {{/info}}
208
209 For this tutorial, we will implement the **createAction** and **showAction** 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)
210
211 Add this method in **BlogEntryController**:
212
213 {{code}}
214
215 protected ERXKeyFilter filter() {
216 ERXKeyFilter personFilter = ERXKeyFilter.filterWithAttributes();
217 personFilter.setAnonymousUpdateEnabled(true);
218
219 ERXKeyFilter filter = ERXKeyFilter.filterWithAttributes();
220 filter.include(BlogEntry.AUTHOR, personFilter);
221 filter.setUnknownKeyIgnored(true);
222
223 return filter;
224 }
225
226 {{/code}}
227
228 Now, let's implement the **creationAction** method:
229
230 {{code}}
231
232 public WOActionResults createAction() throws Throwable {
233 BlogEntry entry = create(filter());
234 editingContext().saveChanges();
235 return response(entry, filter());
236 }
237
238 {{/code}}
239
240 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?
241
242 Last step in the controller: implementing the **showAction** method. Again, the code is simple:
243
244 {{code}}
245
246 public WOActionResults indexAction() throws Throwable {
247 NSArray<BlogEntry> entries = BlogEntry.fetchAllBlogEntries(editingContext());
248 return response(entries, filter());
249 }
250
251 {{/code}}
252
253 That code simply fetch all blog entries and return them in the response.
254
255 We can now go to the next step: adding the routes.
256
257 == Adding the routes ==
258
259 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:
260
261 {{code}}
262
263 ERXRouteRequestHandler restRequestHandler = new ERXRouteRequestHandler();
264 restRequestHandler.addDefaultRoutes(BlogEntry.ENTITY_NAME);
265 ERXRouteRequestHandler.register(restRequestHandler);
266 setDefaultRequestHandler(restRequestHandler);
267
268 {{/code}}
269
270 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.
271
272 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>>http://yourip:someport/cgi-bin/WebObjects/BlogRest.woa_]]//
273
274 == Adding posts and authors with curl ==
275
276 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.
277
278 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>>http://192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa_]], the full curl// command will be:
279
280 {{code}}
281 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
282 {{/code}}
283
284 The response should look this:
285
286 {{code}}
287
288 HTTP/1.0 201 Apple WebObjects
289 Content-Length: 249
290 x-webobjects-loadaverage: 0
291 Content-Type: application/json
292
293 {"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"}}
294
295 {{/code}}
296
297 To get a list of blog entries:
298
299 {{code}}
300
301 curl -X GET http://192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries.json
302
303 {{/code}}
304
305 You can stop the application and proceed to the next step.
306
307 == Adding HTML views for blog posts ==
308
309 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:
310
311 {{code}}
312
313 @Override
314 protected boolean isAutomaticHtmlRoutingEnabled() {
315 return true;
316 }
317
318 {{/code}}
319
320 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**.
321
322 The next step to get it to work is to make **BlogEntryIndexPage** to implements the **er.rest.routes.IERXRouteComponent** interface.
323
324 {{code}}
325
326 import er.rest.routes.IERXRouteComponent;
327
328 public class BlogEntryIndexPage extends WOComponent implements IERXRouteComponent {
329
330 {{/code}}
331
332 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:
333
334 {{code}}
335
336 public NSArray<BlogEntry> entries() {
337 EOEditingContext ec = ERXEC.newEditingContext();
338 return BlogEntry.fetchAllBlogEntries(ec, BlogEntry.CREATION_DATE.descs());
339 }
340
341 {{/code}}
342
343 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**:
344
345 {{code}}
346
347 private BlogEntry entryItem;
348
349 public BlogEntry entryItem() {
350 return entryItem;
351 }
352
353 public void setEntryItem(BlogEntry entryItem) {
354 this.entryItem = entryItem;
355 }
356
357 {{/code}}
358
359 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:
360
361 {{code}}
362
363 <wo:loop list="$entries" item="$entryItem">
364 <p><wo:str value="$entryItem.title" /></p>
365 <p><wo:str value="$entryItem.author.fullName" /></p>
366 </wo:loop>
367
368 {{/code}}
369
370 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.
371
372 If you go to //http:~/~/192.168.0.102:52406/cgi-bin/WebObjects/BlogRest.woa/ra/blogEntries.html_, you will see the list of blog entries!//