Purpose

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.
• Application ID:Screenshots in this tutorial show a blurred Application ID. Your Application ID can be any value assigned automatically while creating the application.
• Schema:If you are accessing an Oracle Application Express workspace in Database Schema Service,you have one schema assigned to you with a schema name that you cannot change. If you are accessing the workspace in an on-premises Oracle database,you may have more than one schema assigned to your workspace by the Oracle Application Express Instance 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 thefiles.zipinto your working directory.
• ExecuteCreate_Employees.sqlfrom the extracted files,to create required database objects.

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. From the Oracle Application Express Home page,select thesql Workshoptab and selectRESTful Services.

2. From the RESTful Services page,select theCreate a New RESTful Serviceoption.

3. A page loads with entries grouped under three different categories named RESTful Services Module,Resource Template,and Resource Handler. Under RESTful Services Module,enteremployeesfor Name,and scroll down further.

4. Under Resource Template,enteremployees/for URI Template to identify your Uniform Resource Identifier (URI),and scroll down further.

5. Under Resource Handler,selectGETfor Method,Queryfor Source Type,CSVfor Format. This identifies the HTTP method to be used for the Resource Handler.
   Enter the following sql query for Source,and clickCreate Module.
   
   select * from employees

6. The GET Handler is created under employees/. To edit its properties,clickGETunder employees/.

7. SelectNofor Requires Secure Access,and clickApply Changes.

8. To test the behavior of the RESTful Service Handler,clickTest.
   
   Note:If your screen does not show a Test button,please ensure that RESTful Services are configured in your Oracle Application Express installation properly.

9. You are prompted to save the file which you can then view using a CSV editor.

10. The CSV format result set is displayed.

11. Let us now create a Handler for the POST method in the same Web Service. ClickCreate Handlerunder employees/.

12. SelectPOSTfor Method andPL/sqlfor Source Type. Enterapplication/jsonfor MIME Types Allowed. SelectNofor Requires Secure Access. Enter the following PL/sql code for Source,and clickCreate.
    
    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;
    

13. Scroll down the page,and clickCreate Parameterto add an OUT parameter to the handler that will return the newly created employee’s ID.

14. Enteremployee_idfor Name and Bind Variable Name. SelectOUTfor Access Method,HTTP Headerfor Source Type,Stringfor Parameter Type,and clickCreate.

15. The OUT parameter is created.

16. ClickCreate Parameteragain to add the following IN parameters to the handler.

    @H_726_502@

    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.

@L_403_19@

Enteremployees/{id}for URI Template,and clickCreate.

ClickCreate Handlerunder employees/{id}.

SelectGETfor Method,Query One Rowfor Source Type,andNofor Requires Secure Access.
Enter the following sql Query for Source,and clickCreate.

select * from employees where employee_id = :id

Scroll down and clickCreate Parameter.

Enteridfor Name and Bind Variable Name. SelectINfor Access Method,and clickCreate.

You want to change the Source Type. Under Parameters,click theidlink under Name.

SelectURIfor Source Type,and clickApply Changes.

Before testing this handler,you have to set a bind variable to pass a value for the input parameter(id). ClickSet Bind Variables >.

Enter103for :ID,and clickTest.

Complete details of the employee with employee_id = 103 is displayed.

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. ClickCreate Template.

2. EnteremployeesFeed/for URI Template,and clickCreate.

3. Under employeesFeed/,clickCreate Handler.

4. SelectGETfor Method,Feedfor Source Type,andNofor Requires Secure Access. Under Source,enter the following sql query,and clickCreate.
   
   select employee_id,first_name
from employees
order by employee_id,first_name

5. UnderemployeesFeed/,clickGETto open the Resource Handler Editor.

6. 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 withemployee_id = 100ishttps://:<hostname>:<port>/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:

   @H_726_502@

   On-Premises	http://localhost:<Port where ords is set up>/ords/<schema name>/<Resource Template Name>/<employee_id> For example:http://localhost:9090/ords/hr/employeesFeed/100 where ords is set up on port9090during Oracle APEX installation,hris the schema name,employeesFeedis the Resource Template name,and100is the employee_id.
   On a Cloud Service	<Service URL as received in the Welcome email from Oracle Cloud>/<Resource Template Name>/<employee_id> For example:https://databasetrial:<user>.db.us2.oraclecloudapps.com/hr/employeesFeed/100 where<user>.db.us2.oraclecloudapps.com/hr/is the Service URL for the cloud service subscription,and100is the employee_id.

7. Select the URI for one of the employee_ids,and copy it to clipboard.

8. 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.

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. ClickCreate Template.

2. EnteremployeesFeed/{id},and clickCreate.

3. Under employeesFeed/{id},clickCreate Handler.

4. SelectGetfor Method,serif; padding: 3px; background-color: transparent; border-radius: 4px; line-height: 1.615; font-style: italic;">select employee_id,first_name
   from employees
   where department_id = :id

5. Scroll down further,and clickCreate Parameter >to add an IN parameter to the handler that will receive the department_id.

6. SelectURIfor Source Type,and clickApply Changes.

7. Before testing this handler,you have to set bind variable to pass a value for the input parameter,id. ClickSet Bind Variables >.

8. Enter60for :ID,and clickTest.

9. 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_idis the first column and will turn into a hyperlink.
   
   For example,the URI for an employee with department_id = 60 ishttp://<hostname>:<port>/ords/hr/employeesFeed/60?page=1where 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,the URI formats are as follows:

   @H_726_502@

   On-Premises

   http://localhost:<Port where ords is set up>/ords/<schema name>/<Resource Template Name>/<department_id>?page=1 For example:http://localhost:9090/ords/hr/employeesFeed/60?page=1 where ords is set up on port9090during Oracle APEX installation,serif; padding: 3px; background-color: transparent; border-radius: 4px; line-height: 1.615;">hris the schema name,serif; padding: 3px; background-color: transparent; border-radius: 4px; line-height: 1.615;">employeesFeedis the Resource Template name and60is the department_id.

   On a Cloud Service

   <Service URL as received in the Welcome email from Oracle Cloud>/<Resource Template Name>/<department_id>?page=1 For example:https://databasetrial:<user>.db.us2.oraclecloudapps.com/hr/employeesFeed/60?page=1 where<user>.db.us2.oraclecloudapps.com/hr/is the Service URL for the cloud service subscription,serif; padding: 3px; background-color: transparent; border-radius: 4px; line-height: 1.615;">employeesFeedis the Resource Template name,and60is the department_id.