Salesforce_Lead_Convert

convert.apex

// Set lead Id here.
Id leadId = '00Q8t0000024px3EAA';

LeadStatus convertStatus = [SELECT Id, MasterLabel FROM LeadStatus WHERE IsConverted = true LIMIT 1];
String leadStatus = convertStatus.MasterLabel;

// Execute Salesforce' lead convert service
Database.LeadConvert lc = new Database.LeadConvert();
lc.setLeadId(leadId);
lc.setConvertedStatus(leadStatus);
Database.LeadConvertResult lcr = Database.convertLead(lc);

// Report an errors
List<Object> convertErrorList;
if (lcr.isSuccess() == false) {
    convertErrorList = new List<Object>();
    for (Database.Error err : lcr.getErrors()) {
        convertErrorList.add(new Map<String, Object> {
            'statusCode' => err.getStatusCode(),
            'message' => err.getMessage(),
            'fields' => err.getFields()
        });
    }
}

// Log the lead convert results
System.Debug(new Map<String, Object> {
    'errors' => convertErrorList,
    'contactId' => lcr.getContactId(),
    'accountId' => lcr.getAccountId(),
    'originalLeadId' => leadId,
    'success' => lcr.isSuccess()
});