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.
Important: Java EE 6 and Java EE 7 projects require GlassFish Server or Oracle WebLogic Server 12c.
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 Web Services manager in the Services window.
Generation of RESTful Java Clients for services registered in the Web Services manager.
Test client generation for testing RESTful web services.
Logical view for easy navigation of RESTful web service implementation
classes in your project.
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.
RESTful Web Services, Persistence, and Entity Classes
RESTful web services in Java rely on the Java Persistence API
to communicate with a database. Specifically, RESTful web services rely on entity classes
and a persistence unit, as defined in the Persistence API. Entity classes are
Java classes that map to objects in a relational database. According
to The Java EE5 Tutorial,
"An entity is a lightweight persistence domain object. Typically
an entity represents a table in a relational database, and each entity
instance corresponds to a row in that table." A persistence unit
consists of the set of entity classes, the data source, the persistence
provider, and the persistence unit's own name, as defined in a persistence.xml file.
You can use NetBeans IDE either to create entity classes and RESTful web services in the same process,
or you can use the IDE to create RESTful web services from existing entity classes.
In this tutorial, you use the RESTful Services from Database wizard to generate entity classes and RESTful web
services in the same process. The wizard automatically generates the persistence unit.
Using a MySQL Database Server
If you use the MySQL database server instead of JavaDB (Derby), you need to register the database server with the IDE and add the sample database to the server.
To use a MySQL database server with this tutorial:
Register your MySQL server in the IDE, if the server is not registered. To register a MySQL server, go to the IDE's Services window, right-click the Databases node, and select Register MySQL server.
A dialog opens in which you type the configuration details of your MySQL server, including administrator user name and password. See "Configuring MySQL Server Properties" in Connecting to a MySQL Database.
Right-click the MySQL server node and select Create Database. The Create MySQL Database dialog opens.
Type sample as the new database name. Grant full access to your root user, or a user of your choice.
Click OK. A dialog opens informing you that sample is the name of a sample database, and asking you if you want to create the tables, objects, and data for this database.
Click Yes. The IDE creates and populates the database, and adds a connection to the database.
Creating RESTful Web Services from a Database
The goal of this exercise is to create a project and generate entity classes and RESTful web services from a database.
This section uses the JavaDB (Derby) database and the jdbc/sample data source. JavaDB is included with the SDK.
The jdbc/sample data source is generated by NetBeans IDE automatically when you install the IDE together with GlassFish.
Creating the Project
To create RESTful web services, you need a Java Web application project.
To create the project:
Choose File > New Project (Ctrl-Shift-N on Linux and Windows, ⌘-Shift-N on MacOS). Under Categories, select Java Web.
Under Projects, select Web Application. Click Next.
The New Web Application wizard opens.
Alternatively, you can create a Maven Web Application. Choose File > New Project (Ctrl-Shift-N on Linux and Windows, ⌘-Shift-N on MacOS). Under Categories, select Maven. Under Projects, select Maven Web Application and click Next.
Under Project Name, enter CustomerDB. Click Next.
Select either Java EE 6 Web or Java EE 7 Web. Under Server, select the server you want to use, but note that Java EE projects require GlassFish server 3.x or 4.x. Click through the remaining options and click Finish.
Important for Maven Projects: In NetBeans IDE 7.2 you cannot set the server when you create a Maven web application.
However, you need to set the server before you can create a persistence unit.
Therefore, after you create the Maven web application, open the project's Properties and set the server in the Run properties. To open the project's Properties, right-click on the Project node and select Properties from the context menu.
Generating Entity Classes and RESTful Services
When you have a Java web application, add entity classes and RESTful web services to the project.
To generate entity classes and RESTful web services:
Right-click the CustomerDB node and
choose New > Other > Web Services > RESTful Web Services from Database. The New RESTful Web Service wizard opens, on the Database Tables panel.
In the Database Tables panel, if you are using the GlassFish server, select the jdbc/sample data source from the Data Source drop-down field.
If you are using Tomcat, select jdbc:derby://localhost:1527/sample. If the Derby database server does not start automatically, you need to start it from the Databases tab in the Services window.
Note for MySQL users: You have to create a new data source. Select New Data Source, give it an arbitrary descriptive name, and select the jdbc:mysql://localhost:3306/sample database connection. You created this connection when you created the sample database on MySQL.
Under Available Tables, select CUSTOMER and then click Add. The DISCOUNT_CODE
table, which has a relationship with the CUSTOMER table, is also automatically
added to the Selected Tables list. If you are using a MySQL database or some versions of Derby, the MICRO_MARKET
table is also added. You now
see the following (Derby version):
Click Next. The Entity Classes page opens. Type entities for the Package name. You now see the following (Derby version).
Note: The RESTful Web Services from Database wizard automatically generates JAXB annotations.
If you generate entity classes for a Java EE application with the Entity Classes from Database wizard, and you might
later want to create RESTful web services from those entity classes, make sure the Generate JAXB Annotations box is checked.
You can also add JAXB annotations by hand to entity classes before running the RESTful Web Services from Entity Classes wizard.
For more information, see NetBeans to Generate Simpler RESTful Web Services.
Click Next. A panel opens in which you can set the name and location of
generated service classes and packages. For Java EE projects, you have the option of changing the name
and location of the REST application configuration class.
Spring framework applications: Register the RESTful resources in the web.xml deployment descriptor.
Do NOT use javax.ws.rs.core.Application.
For this tutorial, accept the defaults and click Finish.
When you click Finish the IDE generates entity and service classes.
In an Java EE project,
the IDE also generates an application configuration class, which is a subclass of Application.
The IDE now generates the RESTful web services.
When the IDE is finished, look in the Projects window.
The generated entity classes are in the entities package and
services are in the service package.
Java EE RESTful web services from a database instantiate EntityManager in each service class.
This removes the need for JPA controller classes and generates simpler code.
Testing the RESTful Web Services
The goal of this exercise is to try out your application.
You will create a new web application for the tests and then use a wizard in the IDE
to generate the tests in the new project.
Choose File > New Project from the main menu.
Select the Web Application project type in the Java Web category. Click Next.
Type WebServicesTest for the project name. Click Next.
Select GlassFish Server as the target server and Java EE 6 Web or Java EE 7 Web as the Java EE version. Click Finish.
Under the CustomerDB project node, right-click the RESTful Web Services node and choose Test RESTful Web Services. A dialog opens asking if you want to generate the test client inside the service project or in another Java web project.
This option lets you work around security restrictions in some browsers.
You can use any Web project, as long as it is configured to deploy in the same server domain as the CustomerDB project.
Select Web Test Client in Project and click Browse.
Select the WebServiceTest project in the Select Project dialog box. Click OK.
The IDE generates the file test-resbeans.html in the WebServiceTest project.
The IDE also automatically starts the server and deploys the CustomerDB application.
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 entities.customer, entities.discountCodes and entities.microMarket.
Click the entities.customer node. In the "Choose method to test" field, select either GET (application/json) or GET (application/xml). Click Test.
The test client sends a request and displays the result in the Test Output section. The test client dispays the Raw View by default. The following image shows the response to an application/xml request.
There are 5 tabs in the Test Output section.
The Tabular View is a flattened view that displays all
the URIs in the resulting document. Currently this view only displays a warning that Container-Containee relationships are not allowed.
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 Sub Resource tab shows the URLs of the root resource and sub resources. When the RESTful web service is based on database entity classes, the root resource represents the database table, and the sub resources represent the columns.
The Headers tab displays the HTTP header information.
The HTTP Monitor tab displays the actual HTTP requests
and responses sent and received.
Exit the browser and return to the IDE.
RESTful Web Services in the Spring Framework
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. However, Spring 3 doesn't contain aopalliance.jar, which the RESTful web service requires to inject an EntityManager object.
Creating a Java Web Application With the Spring Framework
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
to open the Frameworks panel of the wizard. Select Spring Web MVC, then click Finish.
Note. If you already created your project you can add support for the
Spring Web MVC framework by right-clicking the project node in the Projects
window and choosing Properties in the popup menu.
In the Project Properties window, select the Frameworks category and then click Add and select
Spring Web MVC.
Adding aopalliance.jar to the Project
Spring 3 does not contain aopalliance.jar. The application requires this library to inject EntityManager. To fix the problem you need to download this jar and add it to your classpath. See Issue 193626 and the Spring forums.
Right-click your Spring RESTful Web Service project node in the Projects window and
choose Properties in the popup men and then select the Libraries category in the Project Properties window.
Alternatively, you can right-click the Libraries node of the project in the
Projects window and choose Add JAR/Folder.
Click Add JAR/Folder and locate the aopalliance.jar in the file system browser. Click Open.
You will want to use the absolute path reference.
The aopalliance.jar file is now included in your libraries. Click OK.
Creating RESTful Services in the Spring-enabled Project
After you create a Java web application with the Spring framework and add aopalliance.jar
to the project's classpath, run the RESTful Web Service from Database wizard as described in Generating Entities and Services. However, do NOT register RESTful resources with a subclass of javax.ws.rs.core.Application. Instead use the web.xml deployment descriptor. The Spring framework generates a web.xml deployment descriptor in all cases.