Salesforce Merge API authentication using Bearer token - api

Question

Im completely new to Salesforce and API's.
Im trying to make a Merge record call using SOAP API . Using Postman for the same .
I have imported the WSDL to my local , Called Login method to get the serverURL and sessionId.
Using these parameters to make subsequent merge calls .
During the login , I have used username and password to authenticate .
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<login xmlns="urn:enterprise.soap.sforce.com">
<username>username</username>
<password>password+auth_token</password>
</login>
</soap:Body>
</soap:Envelope>
and getting the below response:
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns="urn:enterprise.soap.sforce.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<loginResponse>
<result>
<metadataServerUrl>https://**company_name**--dev.my.salesforce.com/services/Soap/m/54.0/00D0Q0000000QP8</metadataServerUrl>
<passwordExpired>false</passwordExpired>
<sandbox>true</sandbox>
<serverUrl>https://**company_name**--dev.my.salesforce.com/services/Soap/c/54.0/00D0Q0000000QP8/0DF0Q0000004Ct6</serverUrl>
<sessionId>**masked**</sessionId>
<userId>xxx</userId>
<userInfo>
.....
</userInfo>
</result>
</loginResponse>
</soapenv:Body>
</soapenv:Envelope>
Later im making the Merge call using the session ID returned from the above .
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:urn="urn:enterprise.soap.sforce.com"> xmlns:sobject="urn:sobject.enterprise.soap.sforce.com">
<soap:Header>
<urn:SessionHeader>
<urn:sessionId>**masked**</urn:sessionId>
</urn:SessionHeader>
</soap:Header>
<soap:Body>
<merge xmlns="urn:enterprise.soap.sforce.com">
<request>
<masterRecord xsi:type="sobject:Account" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<Id xmlns="urn:sobject.enterprise.soap.sforce.com">0010Q00001abcdefgh</Id>
</masterRecord>
<recordToMergeIds>0010Q00001ijklmnop</recordToMergeIds>
</request>
</merge>
</soap:Body>
</soap:Envelope>
and able to merge the records.
My question is - what should the body be if i donot want to use username and password but use Bearer token.
Can i call the login method without passing username and password?

Answer 1

You might be a victim of XY problem. You can't do it in SOAP API, will REST API be an option?
SOAP API's login call demands username and password (+ optional "security token", extra thing you add to password if you log in from untrusted IP). There are no other ways around it.
REST API has more options for logging in but it'd help if you read up about OAuth2 a bit before diving in. You call login and (similar to SOAP API) get back endpoint to use from now on and access_token. That access_token acts like SOAP APIs session id, you use it in next requests. Most of the time they should be interchangeable, access_token obtained via REST should be good to use in SOAP API calls.
If you already have session id / access token (will look like "00D...!....", first part is org id which you can see in Setup -> Company information for example) - you don't need login call. Call the SOAP API's merge directly and pass that value in <urn:sessionId>.
If you don't have session id, want to log in but without hardcoding username and password in your application... You have LOTS of options. Selecting right method is an art and it depends what are you making. A website, a mobile app? For internal users or community? Will it hold some credentials (for example if it needs sysadmin powers, working in background without human interaction) or will it show users the SF login screen and redirect back to the app? There's even "Internet of Things" stuff for pieces of equipment reporting their status to SF or logging in on device without keyboard (TV, fridge) where you initiate process there and finish on laptop or phone...
If you've never heard about OAuth2 before it's a big topic, "login with Google/Facebook/Twitter/LinkedIn" is just a piece of it. You'll be better off reading some blogs, checking out https://trailhead.salesforce.com/en/content/learn/trails/build-integrations-using-connected-apps or even studying to the Identity and Access Manager certification. Clicking through https://openidconnect.herokuapp.com/ might help too.
There's "username-password flow" which looks almost like SOAP API's login.
There's web server flow and user-agent flow for websites & mobile apps to send user to SF login screen (can be really SF, can be some single sign-on, doesn't matter) and back to the app. So your app doesn't see the password, doesn't see any credentials
There's refresh token option in some of these flows (you logged in once with another method, your app received access_token but also refresh_token. When access expires - app can use refresh_token to silently get back to the system without asking user to log in again. For 60 days for example). So you could still have initial "human authorises connection between the apps" but then it can just work in the background
There's JWT flow which you'll have hard time trying in Postman but there are examples such as this and this. You establish trust between SF and your app by uploading a certificate to Salesforce, marking user as allowed to use this method and then the app sends a special request just with username, no password needed.