Using RESTful Web Services to Implement CRUD Operations in NetBeans 7: Part 2

Purpose

This tutorial demonstrates using RESTful Web Services to implement CRUD database operations in NetBeans 7.

RESTful Web Services use HTTP protocol methods. The HTTP methods such as GET, POST and DELETE can be mapped to create, read, update and delete (CRUD) actions to be performed.Java specification, JAX-RS (JSR 311) provides an API for creating RESTful web services in Java. Jersey is its official reference implementation. It provides additional features through its own APIs such as the Jersey Client API.

This tutorial is the second part of the tutorial, Part-1 of the tutorial, Creating RESTful Web Services in NetBeans 7 : Part 1 covered the Creation and Testing of RESTful Web Services in NetBeans 7.

In this tutorial, you will

Create a Java client application to consume RESTful Web Services.
Implement CRUD operations on the Database using RESTful Web Services.

Prerequisites

Before starting this tutorial, you should have completed Part 1 of this tutorial and met all its prerequisites.

Building a Client Application to consume RESTful Web Services

The following section demonstrates how to create a Java client application PlayerClient, to consume the RESTful webservices created in PlayerServer application.

.	Verify PlayerServer application is running as it creates the RESTful Web Services. Otherwise to start the Server, perform the following steps : a. Open the Projects tab. b. Right-click PlayerServer project. c. Select Run. This action starts the GlassFish server and deploys the application. On successful deployment of the application - a default jsp page with url, http://localhost:8080/PlayerServer/ is opened in the browser displaying "Hello World".
.	To create new Java Project, select File > New Project.
.	Select Java from the Categories column and Java Application from the Projects column and click Next.
.	Perform the below steps: a. Name the project PlayerClient. b. Uncheck Create Main Class. c. Click Finish.

Generating Entity Classes from Database

Implementing CRUD operations on the database, requires creation of Entity Classes to communicate with the database. The following section demonstrates how to create Entity Classes from database.

.	Right-click PlayerClient Project and select New > Entity Classes From Database.
.	a. In the Database Tables window, Database Connection field select jdbc:derby://localhost:1527/playerDB[john on JOHN] from the drop-down list. You see PLAYER and TEAM tables in Available Tables category b. Click Add All You see both the tables PLAYER and TEAM in Selected Tables Category. c. Click Next
.	In the Entity classes Window, enter the Package Name as playerentities and click Next.
.	In the Mappings Options Window, click Finish with default selection.
.	Verify the creation of Entity Classes. a. Select the PlayerClient Project. b. Expand the Source package > playerentities, you see Team.java and Player.java created.

Create Operation Using RESTful Client

The following section demonstrates implemening Create operation using a RESTful Web Service. You will use RESTful Web Service to create a row in PLAYER table.

.	Complete the following steps to create RESTful client in PlayerClient project. a. Right-click the PlayerClient and choose New > Other > Web Services > RESTful Java Client. b. Click Next.
	a. Enter the following details for the fields in the New Restful Java Client window : Class Name: CreatePlayerJerseyClient Package: playerClient Select the REST resource: From Project and Click Browse. b. Select PlayerServer. c. Expand the PlayerServer application. d. Select PlayerFacadeREST[com.playerentity.player]. g. Click OK. h. Click Finish. CreatePlayerJerseyClient.java opens in the code editor.
.	Examine CreatePlayerJerseyClient.java. a. Identify the code snippet where the WebResource is initialized with the URI and path of the RESTful service. b. Observe all the methods of the web service are present which gets, puts, deletes or posts data. Each of the web methods has an application/XML and application/JSON format. create_XML (Object requestEntity)or create_JSON(Object requestEntity)for create operation are two examples.
.	To create a row in the PLAYER table using the RESTful Web Service, make following changes to CreatePlayerJerseyClient.java a. Import the following packages. import java.util.ArrayList; import java.util.List; import playerentities.Player; b. Add the main method. public static void main(String args[])throws UniformInterfaceException { CreatePlayerJerseyClient client1=new CreatePlayerJerseyClient(); ClientResponse response=client1.findAll_XML(ClientResponse.class); GenericType<List<Player>> genericType = new GenericType<List<Player>>() {}; // Returns an ArrayList of Players from the web service List<Player> data= new ArrayList<Player>(); data=(response.getEntity(genericType)); Player p=new Player(); p.setFirstname("Michael"); p.setId(30); p.setJerseynumber(60); p.setLastname("Phelps"); p.setLastspokenwords("Thanks to my fans"); client1.create_XML(p); }
.	In the Projects window, right-click CreatePlayerJerseyClient.java and select Run File.
.	Verify the output. It can be done in two ways: examine the contents of the PLAYER table or Generate Web Services test client. a. To examine the contents of the PLAYER table, complete the below steps: 1. In the Services window, expand the jdbc:derby://localhost:1527/playerDB connection under the Databases node. 2. Right-click the connection and select Refresh. 3. Expand the JOHN schema > Expand Tables Node >PLAYER Table. 4. Right-click PLAYER table node and select View Data. 5. Examine the PLAYER table data, a new row would be created with the details specified for Player object p. b. Generate Web Services test client as explained in Part-1. After the test client is deployed to test the Web Services Client, complete the following steps. 1. Select one resource node, com.playerentity.player. 2. In the "Choose method to test" field, select GET (application/xml). 3. Click Test. 4. Examine the output, response to an application/xml request.You will see the newly created Player object in the XML file.

Retrieve Operation Using RESTful Client

The following section demonstrates how to implement a Retrieve operation on the database using RESTful Web Service. You will use RESTful Web Service to retrieve all the rows in the PLAYER table and display in the console.

.	Complete the following steps to create RESTful client in PlayerClient project. a. Right-click the PlayerClient and choose New > Other > Web Services > RESTful Java Client . b. Click Next.
.	Enter the following details for the fields in the New Restful Java Client window : a. Class Name: GetPlayerJerseyClient b. Package: playerClient c. Select the REST resource: From Project and Click Browse. d. Select PlayerServer e. Expand the PlayerServer application. f. Select PlayerFacadeREST[com.playerentity.player] g. Click OK. h. Click Finish. GetPlayerJerseyClient.java opens in the code editor.
.	To retrieve the contents of the Player table using the RESTful Web Service, make following changes to GetPlayerJerseyClient.java a. Import the following packages. import java.util.ArrayList; import java.util.List; import playerentities.Player; b. Add the main method. public static void main(String args[])throws UniformInterfaceException { GetPlayerJerseyClient client1=new GetPlayerJerseyClient(); ClientResponse response=client1.findAll_XML(ClientResponse.class); GenericType<List<Player>> genericType = new GenericType<List<Player>>() {}; // Returns an ArrayList of Players from the web service List<Player> data= new ArrayList<Player>(); data=(response.getEntity(genericType)); System.out.println("Retreiving and Displaying Players Details"); for( Player players:data ){ System.out.println("FirstName: "+players.getFirstname()); System.out.println("PlayerID: "+players.getId()); System.out.println(" Jerseyno: "+players.getJerseynumber()); System.out.println("LastName: "+players.getLastname()); System.out.println("Last Spoken Words:"+players.getLastspokenwords()); } } Examine findAll_XML() method that is used to retrieve the records from the PLAYER table.
.	In the Projects window, right-click GetPlayerJerseyClient.java and select Run File.
.	Examine the output, PLAYER table content is displayed in the console.

Update Operation Using RESTful Client

The following section demonstrates how to implement Update operation on the database using RESTful Web Service. You will use RESTful Web Service to update a specified row in the PLAYER table.

.	To update a particular row in the PLAYER table using the RESTful Web Service, complete the following step: Make the following changes to main method in CreatePlayerJerseyClient.java. a. Delete the contents of the main method. b. Add the below lines of code to the main method : CreatePlayerJerseyClient client1=new CreatePlayerJerseyClient(); ClientResponse response1= client1.find_XML(ClientResponse.class,"3"); GenericType<Player> genericType = new GenericType<Player>() {}; Player player=response1.getEntity(genericType); System.out.println("FirstName: "+player.getFirstname()); System.out.println("PlayerID: "+player.getId()); System.out.println(" Jerseyno: "+player.getJerseynumber()); System.out.println("LastName: "+player.getLastname()); System.out.println("Last Spoken Words: "+player.getLastspokenwords()); The above code retrieves Player with id equals 3 from the Player Table. The find_XML() method is used to retrieve the Player object with the specified Player id .
.	In the Projects window, right-click CreatePlayerJerseyClient.java and select Run File from the right-click menu.
.	Verify the output, the details Player with id 3 is displayed on the console.
.	Add the below code to the main method to update the retrieved Player object. player.setJerseynumber(100); player.setLastspokenwords(" I will be retiring soon"); client1.edit_XML(player); The above code updates the following fields of the row with player id equals 3 in the PLAYER table : JerseyNumber to 100 and LastSpokenWords to "I will be retiring soon". The edit_XML() method is used to update the record in the PLAYER table.
.	In the Projects window, right-click CreatePlayerJerseyClient.java and select Run File from the right-click menu.
.	Verify the output. It can be done in two ways: examine the contents of the PLAYER table or Generate Web Services test client . a. To examine the contents of the PLAYER table, complete the following steps: 1. In the Services window, expand the jdbc:derby://localhost:1527/playerDB connection under the Databases node. 2. Right-click the connection and select Refresh. 3. Expand the JOHN schema > Expand Tables Node >PLAYER Table. 4. Right-click PLAYER table node and select View Data. 5. The two fields of the Player Table - Jerseynumber and LastSpokenWords of row with PlayerID 3 are updated. b.Generate Web Services test client as explained in Part-1. After the test client is deployed to test the Web Services Client, complete the following steps. 1. Select one resource node, com.playerentity.player. 2. In the "Choose method to test" field, select GET (application/xml). 3. Click Test. 4. Examine the output, response to an application/xml request.You will see the updated Player object with playerID 3 in the XML file.

Delete Operation Using RESTful Client

The following section demonstrates how to implement a Delete operation on the database using RESTful Web Service. You will use RESTful Web Service to delete a specified row in the PLAYER table.

.	To Delete a specified row from the PLAYER table using the RESTful Web Service, perform the following steps: Make the following changes to main method in GetPlayerJerseyClient.java a. Delete the contents of the main method. b. Add the below lines of code to the main method : GetPlayerJerseyClient client1=new GetPlayerJerseyClient(); client1.remove("3"); b. Examine that remove() method is used to delete a record from the Player table with PlayerId, 3.
.	In the Projects window, right-click GetPlayerJerseyClient.java and select Run File from the right-click menu.
.	Verify the output. It can be done in two ways: examine the contents of the PLAYER table or Generate Web Services test client . a. To examine the contents of the PLAYER table, complete the following steps: 1. In the Services window, expand the jdbc:derby://localhost:1527/playerDB connection under the Databases node. 2. Right-click the connection and select Refresh. 3. Expand the JOHN schema > Expand Tables Node >PLAYER Table. 4. Right-click PLAYER table node and select View Data. 5. The row with player id, 3 is deleted from the PLAYER table. b. Generate Web Services test client as explained in Part-1. To test the Web Services Client, complete the following steps. 1. Select one resource node com.playerentity.player. 2. In the "Choose method to test" field, select GET(application/xml). 3. Click Test. 4. Examine the output, player element with details of player id 3 is deleted.

To Delete a specified row from the PLAYER table using the RESTful Web Service, perform the following steps:

Make the following changes to main method in GetPlayerJerseyClient.java

a. Delete the contents of the main method.

b. Add the below lines of code to the main method :

GetPlayerJerseyClient client1=new GetPlayerJerseyClient();
client1.remove("3");

b. Examine that remove() method is used to delete a record from the Player table with PlayerId, 3.

In the Projects window, right-click GetPlayerJerseyClient.java and select Run File from the right-click menu.

Verify the output. It can be done in two ways: examine the contents of the PLAYER table or Generate Web Services test client .

a. To examine the contents of the PLAYER table, complete the following steps:

1. In the Services window, expand the jdbc:derby://localhost:1527/playerDB connection under the Databases node.
2. Right-click the connection and select Refresh.
3. Expand the JOHN schema > Expand Tables Node >PLAYER Table.
4. Right-click PLAYER table node and select View Data.
5. The row with player id, 3 is deleted from the PLAYER table.

b. Generate Web Services test client as explained in Part-1. To test the Web Services Client, complete the following steps.

1. Select one resource node com.playerentity.player.
2. In the "Choose method to test" field, select GET(application/xml).
3. Click Test.
4. Examine the output, player element with details of player id 3 is deleted.