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Salesforce Batch Apex 批处理（三）Database.Stateful接口

接口
2023-03-15 22:06:59 时间

Using State in Batch Apex

Batch处理中，根据特定需求，会有在处理中计算数量的业务，例如现在需要计算所有满足条件的Opportunity表total__c的总额。

具体代码如下，

public with sharing class SummarizeAccountTotal implements Database.Batchable<sObject>{
    public final String Query;
    public integer Summary;
    public SummarizeAccountTotal(String q) {
        Query=q;
        Summary = 0;
    }
    public Database.QueryLocator start(Database.BatchableContext BC){
        return Database.getQueryLocator(query);
    }

    public void execute(Database.BatchableContext BC,List<sObject> scope){
        for(Opportunity opportunityItem : (List<Opportunity>)scope) {
            system.debug('>>>>>>>>>opportunityItem.total__c>>::'+opportunityItem.total__c);
            Summary = Integer.valueOf(opportunityItem.total__c) + Summary;
            system.debug('>>>>>>>>>Summary>>::'+Summary);
        }
    }
    public void finish(Database.BatchableContext BC){
    }
}

现有4条数据，每条数据的total__c的值是1

执行如下操作，预想结果总额应该是4，但是执行结果却是2。

String queryS = 'SELECT Id,Name,total__c FROM Opportunity WHERE DeleteFlg__c = true';
SummarizeAccountTotal batchTest = new SummarizeAccountTotal(queryS);
Database.executeBatch(batchTest, 2);

原因分析：

方法【Database.executeBatch】的第二个参数是2，所以分两次执行，每次执行完execute方法之后，Summary变量都会被清空。

改善方法：

只需实现Database.Stateful接口

public with sharing class SummarizeAccountTotal implements Database.Stateful{

具体代码如下，

public with sharing class SummarizeAccountTotal implements Database.Batchable<sObject>, Database.Stateful{
    public final String Query;
    public integer Summary;
    public SummarizeAccountTotal(String q) {
        Query=q;
        Summary = 0;
    }
    public Database.QueryLocator start(Database.BatchableContext BC){
        return Database.getQueryLocator(query);
    }

    public void execute(Database.BatchableContext BC,List<sObject> scope){
        for(Opportunity opportunityItem : (List<Opportunity>)scope) {
            system.debug('>>>>>>>>>opportunityItem.total__c>>::'+opportunityItem.total__c);
            Summary = Integer.valueOf(opportunityItem.total__c) + Summary;
            system.debug('>>>>>>>>>Summary>>::'+Summary);
        }
    }

    public void finish(Database.BatchableContext BC){
    }
}
String queryS = 'SELECT Id,Name,total__c FROM Opportunity WHERE DeleteFlg__c = true';
SummarizeAccountTotal batchTest = new SummarizeAccountTotal(queryS);
Database.executeBatch(batchTest, 2);

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