Invoking Callouts Using Apex

Invoking Callouts Using Apex

* An Apex callout enables you to tightly integrate your Apex with an external service by making a call to an external Web service or sending a HTTP request from an Apex script and then receiving the response.

 Tightly Couple Architecture

* Apex provides integration with Web services that utilize SOAP and WSDL, or HTTP services (RESTful services).
Note:
* Before any Apex callout can call an external site, that site must be registered in the Remote Site Settings page, or the callout fails.
* Salesforce prevents calls to unauthorized network addresses.
* Callouts enable Apex to invoke external web or HTTP services.
*Apex Web services allow an external application to invoke Apex methods through Web services.

Adding Remote Site Settings

To add a remote site setting:
1. Click Your Name ➤ Setup ➤ Security Controls ➤ Remote Site Settings.
2. Click New Remote Site.
3. Enter a descriptive term for the Remote Site Name.
4. Enter the URL for the remote site.
5. Optionally, enter a description of the site.
6. Click Save.

Types of WSDL's

1. Enterprise WSDL

    * It is a big WSDL which contains information about schema of organization.
    * Strictly Typed: For Integer if we give 3.19 like that then it will not accept and throw error.
    * When schema is modified then we have to recreate new enterprise WSDL.

2. Partner WSDL

    * Loosly Typed: For Integer if we give 3.19 like that then it will accept and not throw error.
    * When schema is modified then it will automatically updated.

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