[Salesforce]スケジュールバッチエラー時メール送信

[Salesforce]スケジュールバッチエラー時メール送信

global class TestBatch implements Database.Batchable<sObject>{

    global Database.querylocator start(Database.BatchableContext BC){
            return Database.getQueryLocator('SELECT Id FROM Account');
    }

    global void execute(Database.BatchableContext BC, List<sObject> scope){
        throw new MyException('test');
    }

    global void finish(Database.BatchableContext BC){
        AsyncApexJob a = [SELECT Id, Status, NumberOfErrors, JobItemsProcessed,
                          TotalJobItems, CreatedBy.Email
                          FROM AsyncApexJob WHERE Id =
                          :BC.getJobId()];
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
        mail.setToAddresses(new String[]{'mokamoto@salesforce.com'});
        mail.setReplyTo('noreply@salesforce.com');
        mail.setSenderDisplayName('Batchプロセス');
        mail.setSubject('Batch完了');
        mail.setPlainTextBody('Batch完了しました。エラー' + a.NumberOfErrors +'件');
        Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });

    }    
    class MyException extends Exception{}
}