Google OCR & Vision API Introduction & Authentication

Hi #Ohana,

Welcome back, it has been a while. In this blog post, we will talk about what Google OCR & Vision APIs are and how to get access token using the Salesforce VF page and apex class.

Introduction to Google Cloud Vision API

GC ( google cloud ) provides the free API which you can use for image labeling, face, logo, and landmark detection, optical character recognition (OCR), and detection of explicit content, into applications.

You can read the complete API documentation from Here

Authentication Overview

All the features of Google Cloud required a valid Access Token to make the request and then return the proper response. To get the access token google uses OAuth 2.O which is a 2 step process.

You can read the process of authentication with Google API from the official document of google cloud. Here is the link for the same.

Step 1 – Create custom metadata types – We will create 2 custom metadata types for authentication purpose.

1.1 – Google Config – The custom metadata types to store the configuration like authentication URL, token URL, client id, client secret &, etc. Below the image of the CM with all the fields

Below are the values for all the fields –

Field	value
access type	offline
authorize uri	https://accounts.google.com/o/oauth2/v2/auth
grant_type	authorization_code
response_type	code
prompt	consent
token URL	https://www.googleapis.com/oauth2/v4/token
Content-Type	application/x-www-form-urlencoded
model	builtin/stable
client secret	YOUR_CLIENT_SECRET
client id	YOUR_CLIENT_ID
scope	space separate scope values for example – https://www.googleapis.com/auth/cloud-platform https://www.googleapis.com/auth/cloud-vision Here is the list of all scope – link
redirect uri	redirect URI is the return URL after authentication. you only need to put the VF page like apex/GoogleAuth and you need to put the complete URL in google app like – https://back-to-basic-dev-ed–c.visualforce.com/apex/GoogleAUTH

Note: – You can get client Id, Client Secret from this page

1.2 – Google Token – This metadata is used to store the Google Access Token and Refresh Token. You only need to create the metadata and the record will be created by code after authentication.

Step 2 – Create Apex Class to create/update custom metadata

You can refer this link for the same

Step 3 – Create Apex Class “GoogleTokenUtility” – the class behind getting access token from Google and then creating the Custom Metadata Record.

Methods in Apex Class

Method Name	Description
getInstance(String filter)	A Reusable Method is used for getting the access token details from metadata Google Token
getConfig(String filter)	A Reusable method to get the google configuration settings from the metadata Google Config
buildQueryAllString	This is the reusable method for the SOQL query with all the fields.
getAuthCode	The method used to get the auth code from google and then this auth code will be used to get access token
getAccessToken	The method used to get the access token for authorized accounts.
doRefreshToken	The method used for refreshing the token if expired
checkIfTokenIsValid	Checks if the token is valid or not.
prepareRequest	Used to prepare the HttpRequest

Step 4 – Create a VF Page “GoogleAUTH“

<apex:page controller="GoogleTokenUtility"  lightningStylesheets="true">
  <apex:form >
      <apex:pageBlock title="Google Authentication">
          <apex:pageblockButtons >
              <apex:commandButton value="Authorize" action="{!getAuthCode}" />
          </apex:pageblockButtons>
      </apex:pageBlock>
  </apex:form>
</apex:page>

Step 5 – Create a new VF Page “CompleteGoogleAuth“

<apex:page controller="GoogleTokenUtility" action="{!getAccessToken}" lightningStylesheets="true">
  <apex:form >
      <apex:pageBlock title="Google Authentication">
          <apex:pagemessages ></apex:pagemessages>
      </apex:pageBlock>
  </apex:form>
</apex:page>

Step 6 – Test the flow

Open the “GoogleAUTH” VF page and click on Preview. Now, Click on the Authorize button.

Thanks for reading 🙂

#Salesforce #Integration