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如果您有很多記錄要處理，例如數據清理或歸檔，則Batch Apex可能是您最好的解決方案。

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假設您要使用Batch Apex處理100萬條記錄。

對于要處理的每批記錄，一次調用批處理類的執行邏輯。

每次調用批處理類時，該作業都會被放置在Apex作業隊列中，并作為離散事務執行。

此功能有兩個很棒的優點：

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在批處理Apex中使用狀態

Batch Apex通常是無狀態的。批處理Apex作業的每次執行均被視為離散事務。

例如，一個包含1,000條記錄并使用默認批處理大小的批處理Apex作業被視為5個事務，每個事務200條記錄。

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假設您有一項業務要求，其中規定，美國公司的所有聯系人都必須以其母公司的Account 地址作為其郵寄地址。

不幸的是，用戶正在輸入沒有正確地址的新聯系人！

編寫一個Batch Apex類，以確保強制執行此要求。

global class UpdateContactAddresses implements Database.Batchable<sObject>, Database.Stateful {// instance member to retain state across transactionsglobal Integer recordsProcessed = 0;global Database.QueryLocator start(Database.BatchableContext bc) {return Database.getQueryLocator('SELECT ID, BillingStreet, BillingCity, BillingState, ' +'BillingPostalCode, (SELECT ID, MailingStreet, MailingCity, ' +'MailingState, MailingPostalCode FROM Contacts) FROM Account ' + 'Where BillingCountry = \'USA\'');}global void execute(Database.BatchableContext bc, List<Account> scope){// process each batch of recordsList<Contact> contacts = new List<Contact>();for (Account account : scope) {for (Contact contact : account.contacts) {contact.MailingStreet = account.BillingStreet;contact.MailingCity = account.BillingCity;contact.MailingState = account.BillingState;contact.MailingPostalCode = account.BillingPostalCode;// add contact to list to be updatedcontacts.add(contact);// increment the instance member counterrecordsProcessed = recordsProcessed + 1;}}update contacts;} global void finish(Database.BatchableContext bc){System.debug(recordsProcessed + ' records processed. Shazam!');AsyncApexJob job = [SELECT Id, Status, NumberOfErrors, JobItemsProcessed,TotalJobItems, CreatedBy.EmailFROM AsyncApexJobWHERE Id = :bc.getJobId()];// call some utility to send emailEmailUtils.sendMessage(job, recordsProcessed);} }

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測試批處理Apex

由于Apex開發和測試是并行進行的

@isTest private class UpdateContactAddressesTest {@testSetup static void setup() {List<Account> accounts = new List<Account>();List<Contact> contacts = new List<Contact>();// insert 10 accountsfor (Integer i=0;i<10;i++) {accounts.add(new Account(name='Account '+i, billingcity='New York', billingcountry='USA'));}insert accounts;// find the account just inserted. add contact for eachfor (Account account : [select id from account]) {contacts.add(new Contact(firstname='first', lastname='last', accountId=account.id));}insert contacts;}static testmethod void test() { Test.startTest();UpdateContactAddresses uca = new UpdateContactAddresses();Id batchId = Database.executeBatch(uca);Test.stopTest();// after the testing stops, assert records were updated properlySystem.assertEquals(10, [select count() from contact where MailingCity = 'New York']);}}

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Create an Apex class that uses Batch Apex to update Lead records

LeadProcessor.apxc

global class LeadProcessor implements Database.Batchable<Sobject> {global Database.QueryLocator start(Database.BatchableContext bc) {return Database.getQueryLocator([Select LeadSource From Lead ]);}global void execute(Database.BatchableContext bc, List<Lead> scope){for (Lead Leads : scope) {Leads.LeadSource = 'Dreamforce';}update scope;} global void finish(Database.BatchableContext bc){ } }

LeadProcessorTest.apxc

@isTest public class LeadProcessorTest {static testMethod void testMethod1(){List<Lead> lstLead = new List<Lead>();for(Integer i=0 ;i <200;i++){Lead led = new Lead();led.FirstName = 'FirstName';led.LastName = 'LastName' +i;led.Company = 'demo' +i;lstLead.add(led);}insert lstLead;Test.startTest();LeadProcessor obj = new LeadProcessor();Database.executeBatch(obj);Test.stopTest();} }

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