REpresentational State Transfer (REST) is an architectural style for
distributed hypermedia systems, such as the World Wide Web. Central to the RESTful
architecture is the concept of resources identified by universal resource identifiers (URIs).
These resources can be manipulated using a standard interface, such as HTTP,
and information is exchanged using representations of these resources. In this tutorial,
you first learn a bit about REST and then you are shown how NetBeans IDE supports
this architectural style.
Tomcat web server 6.0 and/or
GlassFish application server v2 Important: If you use Tomcat with this Tutorial, see the NetBeans Wiki on Tomcat with REST
RESTful web services are services built using the RESTful architectural style.
Building web services using the RESTful approach is emerging as a popular
alternative to using SOAP-based technologies for deploying services on the
internet, due to its lightweight nature and the ability to transmit data
directly over HTTP.
The IDE supports rapid development of RESTful web services using
JSR 311 - Java API for RESTful Web Services (JAX-RS) and Jersey,
the reference implementation for JAX-RS.
In addition to building RESTful web services, the IDE also supports testing,
building client applications that access RESTful web services, and generating code
for invoking web services (both RESTful and SOAP-based.)
Here is the list of RESTful features provided by the IDE:
Rapid creation of RESTful web services from JPA entity
classes and patterns.
Rapid code generation for invoking web services such as
Google Map, Yahoo News Search, and StrikeIron web services by
drag-and-dropping components from the RESTful component palette.
Generation of JavaScript client stubs from RESTful web
services for building RESTful client applications.
Test client generation for testing RESTful web services.
Logical view for easy navigation of RESTful web service implementation
classes in your project.
(NetBeans IDE 6.5) Fully integrated Spring framework, providing Spring transaction handling.
In
this
tutorial, you will be shown how the IDE supports you in generating,
implementing, and testing
RESTful web services.
Generating Entity Classes from a Database
The goal of this exercise is to create a project and generate entity classes from a database.
Choose File > New Project. Under Categories, select Java Web.
Under Projects, select Web Application and click Next.
Under Project Name, enter CustomerDB. Click Next.
Under Server, select GlassFish. Click through the remaining options and click Finish.
Open the Services tab. Under Databases, right-click the Java DB and start it.
Right-click the CustomerDB node and
choose New > Entity Classes from Database. Alternatively, you can select it from the Persistence category in the New File wizard (Ctrl-N).
Note: In NetBeans IDE 6.5, you can generate entity classes and RESTful web services in a single wizard. Instead of choosing New > Entity Classes from Database, choose New > Web Services > RESTful Web Services from Database. Follow the same steps described in the rest of this procedure and in Generating RESTful Web Services from Entity Classes. The Generated Classes step of the New Entity Classes from Database wizard corresponds to Step 3 of Generating RESTful Web Services from Entity Classes. However, if you generate entity classes and RESTful web services separately, as described in this tutorial, you can see in greater detail how the process works.
In the Database Tables panel, select the jdbc/sample data source from the Data Source drop-down field.
Note: On Tomcat, this data source may not exist. In this case, choose New Data Source from the Data Source drop-down field. The Create Data Source dialog opens. Type jdbc/sample in the JNDI Name field. From the Database Connection drop-down field, select jdbc:derby://hostname:1527/sample [app on APP]. Click OK. The dialog closes and you return to the Database Tables panel. See also the RESTful Service on Tomcat tutorial for NetBeans IDE 6.0.
Under Available Tables, select CUSTOMER and then click Add. The DISCOUNT_CODE
table, which has a relationship with the CUSTOMER table, is automatically
added to the Selected Tables list too. You now
see the following:
Click Next.
Under Package, type customerdb. You now see the following.
Click Create Persistence Unit. The following dialog appears.
Click Create. You return to the Entity Classes pane. Click Finish, and the IDE creates the entity classes.
Note: In this tutorial, you skip the optional Mapping Options pane, which lets you change the default annotations used for mapping collections.
Look in the Projects window. You now see
the following.
Generating RESTful Web Services from Entity Classes
The goal of this exercise is to generate
RESTful web services from the entity classes that
you generated in the previous section.
Right-click the package that contains the entity classes
and choose New > RESTful Web Services from Entity Classes.
In the New RESTful Web Services from Entity Classes wizard, click
Add All. After the entity classes appear in the Selected Entity Classes field, click Next. The Generated Classes panel opens.
In the Resource Package field, type customerdb.service, and in the Converter Package field, type customerdb.converter. Accept all other default settings, as shown below:
Here you can see everything that the IDE
will generate for you.
The IDE uses the container-item pattern to
generate the resource classes. For example,
for the Customer entity class, the IDE generates
a container resource called CustomersResource
and an item resource called CustomerResource. Also,
for each resource class, the IDE generates a
converter class used for generating the resource
representation from the corresponding entity
instance, such as CustomersConverter and
CustomerConverter. Furthermore, there is an
additional converter class called reference
converter, such as CustomerRefConverter,
for representing relationships.
Click Finish.
Look in the Projects window. You now see the following:
The RESTful Web Services node in the Projects window
displays all the RESTful web services in your project.
The value between the square brackets, such as [/customers/],
is the value for the URI template. You can also navigate to the
source file by doubling clicking on this node. This view also displays
all the HTTP methods and Sub-resource locator methods. Again, you
can navigate to the methods by double clicking on the nodes.
Now test your application. The IDE provides a useful
utility for testing RESTful web services. You will make use of it
in the next section.
Testing the RESTful Web Services
The goal of this exercise is to try out your application.
Right-click the project node and choose Test RESTful Web Services.
The server starts and the application is deployed.
When deployment is complete, the browser displays your application, with a link for
each of the web services.
If the output window shows an error message that one or more classes fails to exist and the project does not build, add the Jersey libraries to the compile-time libraries. Right-click the project node and select Properties. In the Properties tree menu, select Libraries. Click Add Library and browse for the Jersey libraries.
On the left-hand side is the set of root resources. Here they
are named customers and discountCodes.
Click the customers node. The browser window shows you a list of parameters for testing the Customers service.
You can set the following parameters:
Choose method to test: Choose the GET or POST method and the MIME type from a drop-down list.
Start: First entity to display. Note that the numbering begins with 0, not 1.
Max: Maximum number of entities to fetch. If set to 0, all entities are fetched.
Expand level: An advanced feature. Some services return an infinitely repeating tree hierarchy. This parameter specifies what depth of such hierarchies to display in the Raw View.
Query: An advanced feature. Searches the XML or JSON document according to JPA syntax.
Click on the Methods drop-down list to select GET(application/xml).
Type "3" in the Max field. Leave default values in the other parameters and click Test. The result is displayed in the Test Output section.
There are 4 tabs in the Test Output section.
The Tabular View is a flattened view that displays all
the URIs in the resulting document, which you can navigate
to by clicking on the links.
The Raw View displays
the actual data returned. Depending on which mime type
you selected (application/xml or application/json),
the data displayed will be in either XML or JSON format, respectively.
The Headers Tab displays the HTTP header information.
The HTTP Monitor tab displays the actual HTTP requests
and responses sent and received.
Note that you have 6 results listed although you specified a maximum of 3 entities to display. Open the Raw View tab to see the reason why. Each entity corresponds to a <customer> element, and you have only 3 customers in the test results. However, the Tablular view lists URIs, not entities, and each entity has two URIs, one as an attribute of the parent <customer> element and one as an attribute of the child <discountCode> element. So although there are only 3 customer entities, there are 6 URIs in total.
Exit the browser and return to the IDE.
Adding a Google Map Feature
The goal of this exercise is to add Google map
functionality to our RESTful web services.
Open the CustomerResource class
in the editor.
Add the following method to CustomerResource:
@GET
@Produces("text/html")
public String getGoogleMap() {
// Drag and drop the getGoogleMap operation here
return "";
}
Sign up for a Google map key at http://www.google.com/apis/maps/signup.html. The Google map key request dialog has a field for your website's URL. Type http://localhost:8080 in that field.
In the IDE, open the Services tab and expand the Web Services node. Under Web Services, expand Google. Under Google, expand Map Service.
Drag the getGoogleMap item and drop it into the body of the getGoogleMap method you created in Step 2, just before the return = null; line. The Customize getGoogleMap SAAS dialog opens. Accept the defaults and click OK.
The IDE adds the following try block to the getGoogleMap method in the CustomerResource
class.
@GET
@Produces("text/html")
public String getGoogleMap() {
// Drag and drop the getGoogleMap operation here
try {
String address = "16 Network Circle, Menlo Park";
java.lang.Integer zoom = 15;
String iframe = "false";
RestResponse result = GoogleMapService.getGoogleMap(address, zoom, iframe);
//TODO - Uncomment the print Statement below to print result.
//System.out.println("The SaasService returned: "+result.getDataAsString());
} catch (Exception ex) {
ex.printStackTrace();
}
return "";
}
The IDE also creates the packages org.netbeans.saas and org.netbeans.saas.google, which contain the following classes and resources:
RestConnection – A wrapper around HttpUrlConnection
RestResponse – A wrapper for the HTTP response
googlemapservice.properties – A properties file that stores the API key
GoogleMapService – A service wrapper containing the wrapper methods that uses RestConnection to make calls to the Google Map service.
In the try block of getGoogleMap(), replace the commented-out print statement with the line return result.getDataAsString();. The method now looks like this:
@GET
@Produces("text/html")
public String getGoogleMap() {
// Drag and drop the getGoogleMap operation here
try {
String address = "16 Network Circle, Menlo Park";
java.lang.Integer zoom = 15;
String iframe = "false";
RestResponse result = GoogleMapService.getGoogleMap(address, zoom, iframe);
return result.getDataAsString();
} catch (Exception ex) {
ex.printStackTrace();
}
return "";
}
Open googlemapservice.properties. Paste in the API key you got from Google in Step 3.
Right-click the CustomerDB project node and select Test RESTful Web Services. The IDE undeploys and redeploys your project to the server and then opens a browser window with the test client.
Click customers in the left sidebar. Test criteria for customers open in the main pane. Leave the defaults and click Test. A table of customers opens.
From the table, click customer1. A test window for that customer opens in the main pane. From the drop-down menu, select the text/html MIME type. Click Test. The GoogleMap of 16 Network Circle, Menlo Park opens in the Raw View.
The Google map of the Menlo Park address appears for all customers in the database. To display the Google maps of the actual addresses of the customers, create an instance of Customer for each entity in the database and set the address equal to a concatenation of address variables for each Customer. If you are using an earlier version of the IDE than 6.5, also add a line at the end of the try block to close the instance of Customer. The method now looks like the following (changes in bold):
@GET
@Produces("text/html")
public String getGoogleMap() {
try {
Customer c = getEntity();
String address = c.getAddressline1() + " " + c.getAddressline2() + " " +
c.getCity() + " " + c.getState() + " " + c.getZip();
java.lang.Integer zoom = 15;
String iframe = "false";
RestResponse result = GoogleMapService.getGoogleMap(address, zoom, iframe);
return result.getDataAsString();
} catch (Exception ex) {
ex.printStackTrace();
}
//The close() method is only necessary with versions of NetBeans IDE earlier than 6.5
finally {
PersistenceService.getInstance().close();
}
return "";
}
Test the RESTful web services again. Again, select the text/html MIME type for one of the customers. A Google map of that customer's address in the database now displays in the Raw View. For customer1, the following map displays:
Note: If GoogleMaps cannot find an address, it shows a zoomed in view of the ocean.
RESTful Web Services in the Spring Framework
Starting in NetBeans IDE 6.5 and Jersey 0.8, Jersey is integrated into the Spring Framework. When you create a Java Web application with the Spring framework, a REST-aware servlet is automatically created. The user does not need to perform any additional steps.
To create RESTful Web Services with the Spring framework, repeat the procedures described in the tutorial, with one exception. When you create the Java Web application in the New Project wizard as described in Generating Entity Classes from a Database, after you select the server, click Next instead of Finish. This opens the Frameworks panel. Select Spring Web MVC, then click Finish.
After you create the RESTful services, note the following differences between the Spring project and the project you created without Spring:
The Spring project does not have a class called PersistenceService.java in the customerdb.service package.
CustomerResource.java imports org.springframework.transaction.annotation.Transactional and contains a number of @Transactional annotations.
Both of these differences are due to the Spring framework handling transactions and entity management, whereas in the other project the IDE had to create a class that used javax.transaction.UserTransaction and javax.persistence.EntityManager. The Spring framework results in cleaner code and more efficient transaction handling and entity management.
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