Batch callout: How to upload Attachments from multiple objects (dynamically)?

Question

I am trying to upload an Atttachments based on the selection and criteria from Lightning Component that will be saved to Custom Setting.

For example, the criteria is Opportunity - Stage - Closed Won, I need to query to get all attachments from Closed Won Opportunity and upload them to AWS.

But I don't know how to do it dynamically, please help me.

global class UploadAttachments implements Database.Batchable<sObject> {

global Database.QueryLocator start(Database.BatchableContext BC) {
    String query = 'SELECT Id, Objects__c, Fields__c, Field_Value__c FROM ForUploadCustomSettings__c';
    return Database.getQueryLocator(query);
}

global void execute(Database.BatchableContext BC, List<ForUploadCustomSettings__c> scope) {
    String formattedDateString = Datetime.now().format('EEE, dd MMM yyyy HH:mm:ss z');   
    String host = 's3.amazonaws.com';
    String method = 'PUT';

    HttpRequest req = new HttpRequest();
    Http http = new Http();

    Set<Id> Ids = new Set<Id>();
    for (ForUploadCustomSettings__c so : scope) {
        String objectName = so.Objects__c;
        String fieldName = so.Fields__c;
        String targetValue = so.Field_Value__c;
        // Remove a colon from here
        String query = 'SELECT Id FROM ' + objectName + ' WHERE ' + fieldName + ' =' + targetValue;
        System.debug('Query: ' + query);

        for (ForUploadCustomSettings__c sObj : Database.query(query)) {
            Ids.add((String) sObj.get(objectName));
        }
    }

    List<Attachment> att = [SELECT Id, Name, Body, ContentType FROM Attachment WHERE ParentId IN :Ids];

    List<AWScredentialsSettings__c> values = [SELECT Id, ClientKey__c, SecretKey__c, BucketName__c FROM AWScredentialsSettings__c LIMIT 1];
    if (!att.isEmpty() && !values.isEmpty()) {
        String bucketname = values[0].BucketName__c;
        String key = values[0].ClientKey__c;
        String secret = values[0].SecretKey__c;
        String attachmentBody = EncodingUtil.base64Encode(att[0].Body);
        String filename = att[0].Name;

        req.setMethod(method);
        req.setEndpoint('https://' + host + '/' + bucketname + '/' + filename); // The file should be uploaded to this path in AWS -- ObjectName/Salesforce Id/Secret Files/filename
        req.setHeader('Content-Length', String.valueOf(attachmentBody.length()));
        req.setHeader('Content-Encoding', 'UTF-8');
        req.setHeader('Content-type', att[0].ContentType);
        req.setHeader('Connection', 'keep-alive');
        req.setHeader('Date', formattedDateString);
        req.setHeader('ACL', 'public-read');
        req.setBody(attachmentBody);

        String stringToSign = method+'\n\n\n'+ att[0].ContentType + '\n' + formattedDateString +'\n/'+ bucketname +'/' + filename;
        Blob mac = Crypto.generateMac('HMACSHA1', blob.valueof(stringToSign),blob.valueof(secret));
        String signed  = EncodingUtil.base64Encode(mac);
        String authHeader = 'AWS' + ' ' + secret + ':' + signed;
        req.setHeader('Authorization',authHeader);

        HTTPResponse res = http.send(req);
        System.debug('*Resp:' + String.ValueOF(res.getBody()));
        System.debug('RESPONSE STRING: ' + res.toString());
        System.debug('RESPONSE STATUS: ' + res.getStatus());
        System.debug('STATUS_CODE: ' + res.getStatusCode());
    }
}

global void finish(Database.BatchableContext BC) {

}
}

Answer 1

You need to build out a dynamic query and you'll also need to loop through the scope records so you can run the query and get the IDs for them all.

// Set for storing found ids
Set<string> ids = new set<string>();

//Loop through scope
for(sObject s:scope){

// Set variables
String objectname = s.Objects__c;
String fieldname = s.Fields__c;
String targetvalue = s.Field_Value__c;

// Build query
String query = 'SELECT Id FROM' + objectname + 'WHERE' + fieldname + '= : ' + targetvalue;


// Loop through query and add Ids to set
for(sObject sob:Database.query(query)){

Ids.add((String) sob.get(id));

}

Then you attachment query should yield some results.

Might need some tweaking on phone