How to use batch apex job to handle a list read from json string

Question

I am planning to insert a bunch of sobjects into Salesforce coming from json string (various objects and need to query existing information so data loader won't apply) . How can I use batch job to split it into smaller chunks? Say 10 records in each run?

I have a feeling I should be using Iterable in this case. But haven't found the related sample code though.

Answer 1

There's no rule that says you can't use a built-in List object, if your JSON is formatted that way:

public class BatchInsert implements Database.Batchable<Object> {
  public String jsonString;

  public Object[] start(Database.BatchableContext context) {
    return (Object[])JSON.deserializeUntyped(jsonString);
  }
  public void execute(Database.BatchableContext context, Object[] scope) {
    // Do stuff here
  }
  public void finish(Database.BatchableContext context) {
  }
}

Or, if you have a wrapper class somewhere:

public class BatchInsert implements Database.Batchable<Wrapper> {
  public string jsonString;

  public Object[] start(Database.BatchableContext context) {
    return (Wrapper[])JSON.deserialize(jsonString, List<Wrapper>.class);
  }
  public void execute(Database.BatchableContext context, Wrapper[] scope) {
    // Do stuff here
  }
  public void finish(Database.BatchableContext context) {
  }
}

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You could also use a custom iterator. However, this would involve using JSONParser, which isn't particularly friendly even when you know what you're doing. I can't think of any good reason to use JSONParser, except maybe if you happen to have found some existing Java source that would be compatible. JSON.deserializeUntyped is just as efficient and involves a lot less work.