Creating and Using a RESTful Web Service in Application Express 5.1

This tutorial covers creating a RESTful Web Service and accessing the Web Service through an application in Application Express 5.1. It also covers consuming the Web Service using a REST client.

Time to Complete

Approximately 40 minutes.

Overview

Web Services enable applications to interact with one another over the web in a platform-neutral, language independent environment. In a typical Web Services scenario, a business application sends a request to a service at a given URL by using the protocol over HTTP. The service receives the request, processes it, and returns a response. Web Services are typically based on Simple Object Access Protocol (SOAP) or Representational State Transfer (REST) architectures. RESTful Web Services are result oriented. The scope of the Web Service is found in the URI and the method of the service is described by the HTTP method that is used such as GET, POST, PUT, and DELETE.

The RESTful Web Service Wizard is a set of pages in the SQL Workshop area of Oracle Application Express that help you to create a RESTful Web Service declaratively. Once you have defined a RESTful Web Service, you can call it with a unique Uniform Resource Identifier (URI). RESTful Web Services are organized within Oracle APEX through a hierarchy of a module, a resource template and handlers within a template. The resource template includes a prefix for the URI, which is completed with a final portion of the URI defined by the handler.

This tutorial covers creating a RESTful Web Service declaratively using Oracle Application Express's SQL Workshop tool, and then consuming the same service by creating an application and adding a Web Service Reference to the RESTful Web Service. The RESTful Web Service is also consumed using a REST client.

Please keep in mind the following while running this tutorial:

• Logging into your Oracle Application Express workspace: Your Oracle Application Express workspace may reside in an on-premises Oracle Database or in Oracle Database Cloud Services. The login credentials differ depending on where your workspace is located:
  • Logging into Oracle Application Express in a Oracle Database Cloud Service: Go to the Oracle Help Center for Cloud, and select Platform and Infrastructure. From here, select your Database Cloud Service and the Get Started page will appear.
  • Logging in to Oracle Application Express on-premises: From your browser, go to the location of your on-premises installation of your Oracle Application Express workspace provided by your Workspace Administrator.

  What Do You Need?

  Before starting this tutorial, you should:

  • Have access to an Oracle Database 11.2.x.x or later release, including Enterprise Edition and Express Edition (Oracle Database XE), either on-premises or in a Database Cloud Service.
  • Install Oracle Application Express Release 5.1 into your Oracle Database with RESTful Services configured in Oracle Application Express (for on-premises only).
  • Download and unzip the files.zip into your working directory.
  • Execute Create_Employees.sql from the extracted files, to create required database objects.

  Creating a RESTful Web Service

  In this topic, you create a RESTful Web Service using RESTful Services tool in SQL Workshop. The RESTful Web Service Wizard is a set of pages in SQL Workshop that help you to create a new RESTful Web Service declaratively. The RESTful Web Service calls a specific SQL statement in your database.

  Creating a RESTful Web Service with GET and PUT Resource Handlers

  To create a RESTful Web Service on the Employees table with sample GET and PUT service handlers, perform the below steps:

  1. In the Application Express login page, enter the following login credentials and click Sign In:
     • Workspace: obe
     • Username: obe
     • Password: oracle
     
  2. From the Oracle Application Express Home page, select the SQL Workshop tab and select RESTful Services.
  3. From the RESTful Services page, select the Create a New RESTful Service option.
  4. A page loads with entries grouped under three different categories named RESTful Services Module, Resource Template, and Resource Handler. Under RESTful Services Module, enter employees for Name, and scroll down further.
  5. Under Resource Template, enter employees/ for URI Template to identify your Uniform Resource Identifier (URI), and scroll down further.
  6. Under Resource Handler, select GET for Method, Query for Source Type, CSV for Format. This identifies the HTTP method to be used for the Resource Handler.
     Enter the following SQL query for Source, and click Create Module.

  select * from employees

• The GET Handler is created under employees/. To edit its properties, click GET under employees/.
• Select No for Requires Secure Access, and click Apply Changes.
• To test the behavior of the RESTful Service Handler, click Test.

  Note: If your screen does not show a Test button, please ensure that RESTful Services are configured in your Oracle Application Express installation properly.

• You are prompted to save the file which you can then view using a CSV editor.
• The CSV format result set is displayed.
• Let us now create a Handler for the POST method in the same Web Service. Click Create Handler under employees/.
• Select POST for Method and PL/SQL for Source Type. Enter application/json for MIME Types Allowed. Select No for Requires Secure Access. Enter the following PL/SQL code for Source, and click Create.

  declare
  id employees.employee_id%TYPE;
  begin
  id := employees_seq.nextval;

  insert into employees
  (employee_id,first_name, last_name, email, hire_date, job_id)
  values
  (id, :first_name, :last_name, :email, to_date(:hire_date, 'DD-MM-YYYY'),
  :job_id);

  :employee_id := id;
  end;
  

• Scroll down the page, and click Create Parameter to add an OUT parameter to the handler that will return the newly created employee’s ID.
• Enter employee_id for Name and Bind Variable Name. Select OUT for Access Method, HTTP Header for Source Type, String for Parameter Type, and click Create.
• The OUT parameter is created.
• Click Create Parameter again to add the following IN parameters to the handler.

  Name	Bind Variable Name	Access Method	Parameter Type
  first_name	first_name	IN	String
  email	email	IN	String
  last_name	last_name	IN	String
  hire_date	hire_date	IN	String
  job_id	job_id	IN	String

  

  In the next section, you create a new template to retrieve JSON result set based on Query One Row with a bind variable.

  Creating a Resource Handler with Query One Row

  In this section, you will create a RESTful Service that provides detailed information of an employee, given the employee id. The result is returned in JSON format. Perform the following steps:

  1. Click Create Template.
  2. Enter employees/ for URI Template, and click Create.
  3. Click Create Handler under employees/.
  4. Select GET for Method, Query One Row for Source Type, and No for Requires Secure Access.
     Enter the following SQL Query for Source, and click Create .

  select * from employees where employee_id = :id

• Scroll down and click Create Parameter.
• Enter id for Name and Bind Variable Name. Select IN for Access Method, HTTP Header for Source Type, String for Parameter Type, and click Create.
• You want to change the Source Type. Under Parameters, click the id link under Name.
• Select URI for Source Type, and click Apply Changes.
• Before testing this handler, you have to set a bind variable to pass a value for the input parameter(id). Click Set Bind Variables >.
• Enter 103 for :ID, and click Test.
• Complete details of the employee with employee_id = 103 is displayed.

Creating a Resource Handler with Employees Feed

In this section, you will be creating a RESTful service of a feed source type. The feed results are rendered in JSON format. Each item in the feed contains a summary of a resource and a hyperlink to a full representation of the resource. Perform the below steps:

1. Click Create Template.
2. Enter employeesfeed/ for URI Template, and click Create.
3. Under employeesfeed/, click Create Handler.
4. Select GET for Method, Feed for Source Type, and No for Requires Secure Access. Under Source, enter the following SQL query, and click Create.
   
   select employee_id, first_name
   from employees
   order by employee_id, first_name
5. Under employeesfeed/ , click GET to open the Resource Handler Editor.
6. Scroll down the page, and click Test.
7. The results are rendered in JSON format. Each item consists of a URI which contains the base URI from this RESTful Service, and the value of employee_id used as the parameter. For the Feed source type, the first column must be a unique identifier. It will be transformed into a hyperlink when this RESTful Service is called.
   In this example, employee_id is the first column and will turn into a hyperlink.

For example, in the screenshot shown below, the URI for an employee with employee_id = 100 is https://: :/ords/hr/employeesfeed/100

Note: The URI shown in this example is specific to the database On-Premise subscription used for executing this tutorial, and it might be different for you. The value of the URI also depends on whether you are performing this tutorial On-Premises or on a Cloud Service. In general, the URI formats are as follows:



• Select the URI for one of the employee_ids, and copy it to clipboard.
• Open a browser, paste the copied URI, and press Enter. Notice that the details of that particular employee are returned as a JSON result set.

Creating a Resource Handler with Employees Feed for a Given Department

In this section, you will be creating a RESTful service of a feed source type given the Department ID. The feed results are rendered as JSON. Perform the below steps:

1. Click Create Template.
2. Enter employeesfeed/, and click Create.
3. Under employeesfeed/, click Create Handler.
4. Select Get for Method, Feed for Source Type, and No for Requires Secure Access. Under Source, enter the following SQL query, and click Create.

select employee_id, first_name
from employees
where department_id = :id

• Scroll down further, and click Create Parameter > to add an IN parameter to the handler that will receive the department_id.
• Enter id for Name and Bind Variable Name. Select IN for Access Method, HTTP Header for Source Type, String for Parameter Type, and click Create.
• You want to change the Source Type. Under Parameters, click the id link under Name.
• Select URI for Source Type, and click Apply Changes .
• Before testing this handler, you have to set bind variable to pass a value for the input parameter, id. Click Set Bind Variables > .
• Enter 60 for :ID, and click Test .
• The results are rendered in JSON format. Each item consists of a URI which contains the base URI from this RESTful Service, and the value of department_id used as the parameter. For the Feed source type, the first column must be unique identifier and will be transformed into a hyperlink when this RESTful Service is called.
  In this example, department_id is the first column and will turn into a hyperlink.

  For example, in the screenshot shown below, the URI for an employee with department_id = 60 is http:// :/ords/hr/employeesfeed/60?page=1 where page=1 indicates that these results are part of page 1. If there are many records in the result set, the results can span across page 2 and so on.
  
  Note: The URI shown in this example is specific to the database On-Premise service subscription used for executing this tutorial, and it might be different for you. The value of the URI also depends on whether you are performing this tutorial On-Premises or on a Cloud Service. In general, the URI formats are as follows:

  The result in JSON format" />

  Creating a RESTful Web Service Reference in Oracle Application Express

  In this topic, you consume the RESTful Web Service in Oracle Application Express by creating a database application and by creating a Web Service Reference in the application. You create a form and report page that uses the web service.

  Note: If you are executing this tutorial On-Premises, make sure you have granted the connect privileges by executing the APEX_ACL.sql script from the files.zip folder that you had downloaded and unzipped in the Prerequisites section of this tutorial.
  

  1. From the Oracle Application Express home page, click the down arrow next to App Builder, and select Database Applications.
  2. Click the Create icon.
  3. Accept the default, and click Next >.
  4. Enter RESTful Web Services Demo for Name, and click Next >.
  5. Click Next >.
  6. Accept the default, and click Next >.
  7. Select Application Express Accounts for Authentication Scheme, and click Next >.
  8. Click Create Application.
  9. The application is created. Click Shared Components.
  10. Under Data References, click Web Service References.
  11. Click Create >.
  12. Select REST for What type of Web reference would you like to create, and click Next >.
  13. Enter employees for Name. Select GET for HTTP Method and No for Basic Authentication. For the URL, enter the Web Reference URI for the GET Service Handler which was created in the first section of this tutorial.

  As explained in the below table, your URI depends on the location of your Oracle Application Express instance, whether On-Premises or on a Database Cloud Service.

  This RESTful Web Service does not require an HTTP Header parameter. So, scroll down and click the Delete Header icon.

  

• Click Next >.
• There are no parameters defined for the GET Service Handier. So, click the Delete Parameter icon for Input Parameters.
• Click Next >.
• Now, you have to define the REST Outputs. Select Text for Output Format. Enter comma for Parameter Delimiter, and \n for New Record Delimiter.
  Under Output Parameters, enter Employee ID for Name and 1 for Path. Select String for Type, and click Add Parameter.
• Similarly, add the following Output Parameters, and click Create .

  Name	Path	Type
  Name	2	String
  Hire Date	6	String
  Job Id	7	String

  

• Click the View Report icon.
• Click the Test icon for employees.
• Employees' details is displayed in the Response section. Click Cancel.
• Click Application in the breadcrumb.
• Click Create Page >.
• Click the Form icon.
• Click the Report and Form on Web Service icon.
• Select employees for Web Service Reference, doREST for Operation, and click Next >.

  Note: Employees appears in the select list for Web Service Reference because you added it under Web Service References in Shared Components.

• Click Next >.
• Click Next >.
• Select all four parameters, that is, employee Id, Name, Hire Date, and Job Id. Click Next >.
• Accept the default an click Next >.
• Click Create.
• The new page is created. Click Save and Run Page.
• Enter your Oracle Application Express credentials, and click Log In.
• Click Submit.
• The Web Service is executed, and the results displayed.

Consuming the RESTful Web Service Created in Oracle Application Express Using a REST Client

In this section, you consume the Web Service that you have created in Oracle Application Express, using a REST Client.

Note: For the purpose of this tutorial, we will be using the RESTClient add-on in Firefox to demonstrate how to consume the RESTful Web Service created in APEX. You can also use other REST Clients such as, REST Easy and RESTer to perform these steps in Firefox. If you are using Google Chrome, you can install add-ons such as Postman to perform the steps.

1. Open Firefox and install the RESTClient, a debugger for RESTful web services add-on to your browser.
2. Open the installed add-on in your browser.
3. To fetch the details of an employee, select GET as the Request Method. For the URL, enter the Web Reference URI for the GET Service Handler which was created in the first section of this tutorial.

As explained in the below table, your URI depends on the location of your Oracle Application Express instance, whether On-Premises or on a Database Cloud Service. In this example, https://: :/ords/hr/employees/employees is the URL used for the On-Premise machine.

Click SEND.

• Select the Response Body (Preview) tab to view all the employee records.
• To insert new values into the employees table, under Headers, select Custom Header.
• Enter Content-Type as Name, application/json as Value, and click OK .
  
• In the RESTClient page, enter POST as the request method, enter the same URL as that of the GET method, enter the following code in the Request Body, and click SEND. <
  "first_name":"Supriya",
  "last_name":"Ananth",
  "email":"SUPANANT",
  "hire_date":"13-05-2001",
  "job_id":"AD_PRES"
  >
• Under Response, select Responses Header. You see that the new employee's information is added into the Employees table. The newly created employee’s ID is returned back to the application.
  

Summary

In this tutorial, you have learned how to:

• Create a RESTful Web Service with various Resource Handlers using Oracle Application Express.
• Create a RESTful Web Service Reference in Application Express.
• Consume the Web Service created in Application Express using a REST client.
  

Want to Learn More?

• Using RESTful Services
• Oracle Cloud Home Page