Implementing Web Services

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. You can incorporate calls with external Web services in applications developed in Application Builder.

Web services are typically based on Simple Object Access Protocol (SOAP) or Representational State Transfer (REST) architectures. SOAP is a World Wide Web Consortium (W3C) standard protocol for sending and receiving requests and responses across the Internet. SOAP messages can be sent back and forth between a service provider and a service user in SOAP envelopes. RESTful Web services are resource 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, HEAD, and DELETE.

SOAP offers two primary advantages:

• SOAP is based on XML, and therefore easy to use.
• SOAP messages are not blocked by firewalls because this protocol uses simple transport protocols, such as HTTP.
  
  
  REST offers similar advantages:
• REST messages are also not blocked by firewalls because this protocol uses the HTTP protocol.
• REST requests do not require the overhead of XML and SOAP envelopes and inputs are typically provided in the URI.

Topics:

• Understanding Web Service References
• Working with SSL Enabled Web Services
• Creating a Web Service Reference Based on a WSDL
• Creating a Web Service Reference Manually
• Creating a RESTful Web Service Reference
• Using the Web Service Reference Repository
• Testing a Web Service Reference Created from a WSDL
• Testing a Web Service Reference Created Manually
• Testing a REST Web Service Reference
• Creating an Input Form and Report on a Web Service
• Creating a Form on a Web Service
• Invoking a Web Service as a Process
• Editing a Web Service Process
• Viewing a Web Service Reference History
• Exposing a Report Region as a RESTful Web Service

Exposing a Report Region as a RESTful Web Service

RESTful Web services, that are callable with a URL and return either JSON or XML, can be exposed in report regions. To expose a report region as a RESTful Web service, the following steps must be performed:

1. The instance administrator must enable the REST provider feature in instance settings.
2. A developer must enable RESTful access to a report region.
3. The page that contains the report must not require authentication.
   
   

   Enabling RESTful Access to a Report Region

   To enable RESTful access to a report regions, you must make the page public so no authentication is required and enable the report for RESTful access.
   To make a page public:
   

   1. On the Workspace home page, click the Application Express.
   2. Select an application.
   3. Select the page that contains the report you want to enable.
      The Page Definition appears.
   4. Under Page, click the edit icon.
   5. Under Security, select Page is Public from the Authentication list.
   6. Click Apply Changes.

   To enable a report region for RESTful access:
   

   1. On the Workspace home page, click Application Builder.
   2. Select an application.
      Application Builder appears.
   3. Select the page that contains the report you want to enable.
      The Page Definition appears.
   4. Under Regions, click the name of the region that contains the report you want to enable.
   5. Under Attributes, enter a value for Static ID field. This value is used to access the report RESTfully.
   6. From the Enable RESTful Access List, select Yes.
   7. Click Apply Changes.

   Accessing a RESTful Enabled Report Region from a Web Service Client

   Once you enabled a report for RESTful access, you need to know the endpoint URL and parameters to pass to the RESTful Web service. The endpoint URL is similar to the URL used to access this instance of Oracle Application Express followed by the resource apex_rest.getReport. For example:
   http://apex.oracle.com/apex/apex_rest.getReport
   

   Tip:

   If your client uses the POST method, you must also set the HTTP Header, Content-Type, to the value application/x-www-form-urlencoded.

   Name	Default	Required	Description
   app	N/A	Yes	The numeric ID or alias of the application that contains the RESTful enabled report.
   page	N/A	Yes	The numeric ID or alias of the page that contains the RESTful enabled report.
   reportid	N/A	Yes	The Static ID attribute of the RESTful enabled report.
   parmvalues	null	No	Values for the report parameters can be sent in a comma separated list. For example: CLERK,10
   lang	en	No	Sets the NLS environment variables prior to running the report based on the language passed in. For example: de
   output	xml	Yes	This determines whether XML or JSON will be returned to the client. Domain of possible values are: xml, json

   The apex_rest service also has an operation to allow discoverability of RESTful enabled reports, given an application ID or alias. The response is an XML document with a description of all reports that can be accessed by RESTful Web services. This service is invoked with a URL similar to the following:
   http://apex.oracle.com/apex/apex_rest.getServiceDescription?app=691
   In the URL above, 691 is the numeric ID of an application. The document returned is similar to the following:
   

   <?xml version="1.0"?>
   <urn:getServiceDescriptionResponse xmlns:urn="urn:oasis:names:tc:wsrp:v1:types">
           <urn:requiresRegistration>false</urn:requiresRegistration>
           <urn:offeredPortlets>
                       <urn:PortletDescription>
                                 <urn:portletHandle>employees</urn:portletHandle>
                                 <urn:markupTypes>
                                           <urn:mimeType>application/xml</urn:mimeType>
                                           <urn:mimeType>application/json</urn:mimeType>
                                 </urn:markupTypes>
                                 <urn:groupID>1</urn:groupID>
                                 <urn:description/>
                                 <urn:title>EMP</urn:title>
                                 <urn:keywords>
                                   <urn:value>P1_JOB</urn:value>
                                         <urn:value>P1_DEPTNO</urn:value>
                                 </urn:keywords>
                       </urn:PortletDescription>
           </urn:offeredPortlets>
   </urn:getServiceDescriptionResponse
   

   The portletHandle maps to the Static ID of the report region or the reportid parameter in the REST request. The groupID maps to the page id or the page parameter in the REST request. Finally, any parameters used by the SQL report are listed as children of the keywords node.

Viewing a Web Service Reference History

The Web Services History displays changes to Web service references for the current application by application ID, Web service references name, developer, and date.

To view a history of Web service reference changes:

1. On the Workspace home page, click the Application Builder icon.
2. Select an application.
3. Click Shared Components.
   The Shared Components page appears.
4. Under Logic, click Web Service References.
5. Click History.

Note:

The History button only appears on the Web Service Reference page after you have created a Web service reference.

Editing a Web Service Process

After you create a process of type Web service on a Web service reference created from a WSDL or a RESTful style Web reference, you can change the attributes of the input and output parameters to the service.

To edit a Web service process:

1. Create a Web service process. See "Invoking a Web Service as a Process".
2. Navigate to the Page Definition containing the Web service process.
3. Select the process name.
   The Edit Page Process page appears.
4. To map an input parameter to a static value:
   
   1. Scroll down to Web Service Input Parameters.
   2. Enter a value in the Value field, adjacent to the appropriate parameter name.
5. Click Apply Changes.

Creating a Form on a Web Service

The Create Form on Web Service Wizard creates a form and a submit button. You can execute this wizard after creating the Web service reference from a WSDL or on a RESTful style Web service, or from the Page Definition.

Use this wizard when you expect a scalar result from the Web service. A Web service that looks up a stock price is a good example because the input is a stock symbol and the output is the scalar value price.

Creating a Form After Creating a Reference

To create a form after creating a Web Service Reference:

1. Create the Web service reference. See "Creating a Web Service Reference Based on a WSDL", Creating a RESTful Web Service Reference , and Creating a Web Service Reference Manually.
2. After the Web service references has been added, select Create Form on Web Service.
3. For Choose Service and Operation:
   
   1. Web Service Reference - Select the Web service reference.
   2. Operation - Select the method to be executed. For RESTful style Web references, doREST will be selected automatically. The Operation option will not appear for Manual style Web references.
4. For Identify Page and Region Attributes, review the page and region attributes. If the page you specify does not exist, the wizard creates the page for you.
5. For Items for Input Parameters:
   
   1. Identify which items to add. To include an item, select Yes in the Create column. Otherwise, select No.
   2. If necessary, edit the item label.
6. For Items for Output Parameters (this step is bypassed for Manual style Web references):
   
   1. Identify which items need to be added. To include an item, select Yes in the Create column. Otherwise, select No.
   2. If necessary, edit the item label.
7. If applicable, specify the Item Names and Item Labels for basic authentication.
   Note that this step only appears if basic authentication was specified for this Web service reference when it was created.
8. Click Finish.

Creating a Form by Adding a New Page

If you have an existing Web service reference, you can create form by adding a new page.
To create a form by adding a new page:

1. Create the Web service reference. See "Creating a Web Service Reference Based on a WSDL", Creating a RESTful Web Service Reference , and Creating a Web Service Reference Manually.
2. Create a new page.
   In the Create Page Wizard:
   
   1. Select Form.
   2. Select Form on Web Service.
3. For Web Service Reference and Operation, select the Web service reference and operation (that is, the method to be executed). For RESTful style Web references, doREST will be selected automatically. The Operation option does not appear for Manual style Web references.
4. For Identify Page and Region Attributes, review the page and region attributes. If the page you specify does not exist, the wizard creates the page for you.
5. For Items for Input Parameters:
   
   1. Identify which items need to be added. To include an item, select Yes in the Create column. Otherwise, select No.
   2. If applicable, specify the Item Names and Item Labels for basic authentication.
      Note that this step only appears if basic authentication was specified for this Web service reference when it was created.
6. For Items for Output Parameters (this step is bypassed for Manual style Web references):
   
   1. Identify which items need to be added. To include an item, select Yes in the Create column. Otherwise, select No.
   2. If necessary, edit the item label.
7. Click Finish.

Testing a REST Web Service Reference

After you have created a Web service reference, you can test it on the Test Web Service Reference page.

To test a Web service reference:

1. Navigate to the Web Service References page. See "Accessing the Web Service References Page".
2. From View, select Report.
3. Click the Run icon adjacent to the Web Service reference name.
   The Test Web Service Reference page appears. The Web service name and URL endpoint display at the top of the page.
4. In the URL and Proxy Override fields, optionally edit the values for the test.
5. If required, enter the username and password under Basic Authentication.
6. Under HTTP Headers, enter appropriate values.
7. Under Input Parameters, enter appropriate values.
8. Click Test.
   The message response appears at the bottom of the page.

Testing a Web Service Reference Created Manually

After you have created a Web service reference, you can test it on the Test Web Service Reference page.

To test a Web service reference:

1. Navigate to the Web Service References page. See "Accessing the Web Service References Page".
2. From View, select Report.
3. Click the Run icon adjacent to the Web Service reference name.
   The Test Web Service Reference page appears. The Web service name and URL endpoint display at the top of the page.
4. If required, enter the username and password under Basic Authentication.
5. In SOAP Envelope text area, optionally edit the SOAP request envelope.
6. Click Test.
   The message request and response appear at the bottom of the page.

Testing a Web Service Reference Created from a WSDL

After you have created a Web service reference, you can test it on the Test Web Service Reference page.

To test a Web service reference:

1. Navigate to the Web Service References page. See "Accessing the Web Service References Page".
2. From View, select Report.
3. Click the Run icon adjacent to the Web Service reference name.
   The Test Web Service Reference page appears. The Web service name and URL endpoint display at the top of the page.
4. From Operation, select an operation (that is, the method to be executed).
5. Under Input Parameters, enter the appropriate values.
6. Click Test.
   The message request and response appear at the bottom of the page.

Using the Web Service Reference Repository

Web service references are stored in the Web Service Reference Repository.

To access the Web Service References Repository:

1. On the Workspace home page, click Application Builder.
2. Select an application.
3. Click Shared Components.
   The Shared Components page appears.
4. Under Logic, click Web Service References.
   The Web Service Reference page appears.
   A Search bar at the top of the page. Available controls include:
   
   • Search columns icon - Resembles a magnifying glass. Click this icon to narrow your search. To search all columns, select All Columns.
   • Text area - Enter case insensitive search criteria (wildcard characters are implied) and then click Go.
   • Go button - Executes a search or applies a filter.
   • View. Use this control to toggle between icon and report views. To change the view, click these icons:
     
     • Icons (the default) displays each Web service reference as a large icon. To edit a Web service reference, click the appropriate icon.
     • Report displays each Web service reference as a line in a report.
   • Actions menu - Displays the Actions menu. Use this menu to customize the report view.
5. Click the View Report icon.
6. In report view you can:
   
   • Edit a reference by clicking the reference name.
   • Test a reference by clicking the Run icon.
   • View details about a reference by clicking the View icon. Note that this option is not available for manually created or REST Web service references.

Creating a RESTful Web Service Reference

To utilize a RESTful Web service from your application, you must create a RESTful Web service reference.

To create a RESTful Web service reference:

1. Navigate to the Web Service References page. See "Accessing the Web Service References Page".
2. Click Create.
3. Select REST and click Next.
4. For REST Details, specify the following:
   
   1. Name - Enter a name to identify the reference.
   2. URL - Enter the URL endpoint of the Web service.
   3. Proxy - Enter a proxy to override the application proxy for this service (optional).
   4. HTTP Method - Choose the http method used for the request to the Web service. Select GET, HEAD, POST, PUT or DELETE.
   5. Basic Authentication - Select Yes to require HTTP Basic Authentication. Otherwise, select No.
   6. HTTP Headers - Enter the names of the HTTP headers to send with the request.
   7. Click Next.
5. For REST Input parameters, specify the following:
   
   1. Name - Enter the name of the input parameter expected by the method.
   2. Type - Select the input type.
   3. Click Add Parameter.
   4. Repeat steps a though c for each expected input.
   5. Click Next.
6. For REST Output parameters, specify the following:
   
   1. Output Format - Select XML or Text for the response format expected from the Web service.
   2. XPath to Output Parameters (XML only) - Enter an XPath expression to the relevant part of the response.
   3. Response Namespace (XML only) - Enter the namespace corresponding to the Response XPath.
   4. Parameter Delimiter (Text only)- Enter the character or sequence that separates parameters returned from the Web service. Use \n to indicate a new line and \t to indicate a tab character.
   5. New Record Delimiter (Text only) - Enter the character or sequence that determines a new record in a text response from the Web service. Use \nto indicate a new line and \t to indicate a tab character.
   6. Name - Enter the name of the output parameter returned by the method.
   7. Type - Select the output type.
   8. Click Add Parameter.
   9. Repeat steps f though h for each returned output parameter.
   Note:

   Click Test to send a request to a RESTful Web service and see the response. This test process will help you in specifying the appropriate Output parameters.
7. Click Create.

The Create Web Service Reference Success page appears. The Web service reference is added to the Web Service References Repository.