Web services Salesforce Web服务错误

我从调用Web服务的类收到以下错误

"You have uncommitte​d work pending. Please commit or rollback before calling out"

下面是调用Web服务的类：

global class myWS   
{   

   WebService static string invokeExternalWs(string childValue, string parentValue)   
    {   
        HttpRequest req = new HttpRequest();   
        req.setEndpoint('https://externalURL/Services');   
        req.setMethod('POST');   
        req.setHeader('Content-Type', 'text/xml; charset=utf-8');   
        req.setHeader('SOAPAction', 'http://externalService/externalMethod');  
        string b = '--soap request goes here--';   
        req.setBody(b);   
        Http http = new Http();   
        try {   
          //Execute web service call here 
          String xObjectID ='';   
          HTTPResponse res = http.send(req);
          Dom.Document doc = res.getBodyDocument();
          String soapNS = 'http://schemas.xmlsoap.org/soap/envelope/'; 
          Dom.XmlNode root = doc.getRootElement();
          for(dom.XmlNode node1 : root.getChildElements()) {
               for(dom.XmlNode node2 : node1.getChildElements()) {
                   for(dom.XmlNode node3 : node2.getChildElements()) {
                      for(dom.XmlNode node4 : node3.getChildElements()) {
                          xObjectID = node4.getText();
                       }
                   }
               }
             }

         return xObjectID;
       } catch(System.CalloutException e){   
          return 'ERROR:' + e;   
     }          
}   
}

更新：这是我执行myWS的类

public void applyURLString(ID ArgBuildID) {

    Builder__c current_build = [SELECT id, name, LLURL__c, column1, column2, Opportunity__c
                FROM Builder__c
                WHERE id = :ArgBuildID];

        if(current_build.LLURL__c == null || current_build.LLURL__c.trim().length() == 0)
            {

                String tmpFolderName = current_build.column1 + ' - ' + current_build.column2;

                String LLWSResultPattern = '[0-9]{2,}';

                String myWSXMLResult = myWS.invokeExternalWs(tmpFolderName,'test');

                Boolean LLWSPatternMatched = pattern.matches(LLWSResultPattern,myWSXMLResult);
                if(LLWSPatternMatched)
                {
                    Opportunity oppt = [SELECT Id,Name 
                                        FROM Opportunity 
                                        WHERE Id = :current_build.Opportunity__c
                                        LIMIT 1];   
                    oppt.LLURL__c = 'https://someService/' + myWSXMLResult;
                    update oppt;
                } 
            } 
    }

更新#2-这里是执行applyURLString（）的地方。这是在HTTP请求之前执行DML的唯一位置。但我需要新的建筑商记录的ID

Builder__c insertBuild = new Builder__c();      
insertBuild.Opportunity__c = opportunityId;
insertBuild.Product_Group__c = selectedBuild.Product_Group__c;
insertBuild.Manual_Build_Product__c = selectedBuild.Manual_Build_Product__c;

insert insertBuild;

applyURLString(insertBuild.Id);

---

你知道为什么会发生这个错误吗？

@JCD建议使用@future注释解决了我的问题。再次感谢

我们需要查看调用该类的类/触发器-如果在更新数据库后进行调用，您将收到此消息。好的，我添加了上面的执行代码。再次更新（#2），我认为是代码导致了问题。在调用applyURLString之前，您有一个DML语句（insert INSERTBILD；）。正如我之前所说，如果在同一事务中更新数据库后尝试调用，则会收到此消息。我可能会建议将applyURLString方法作为未来的调用来解决这个问题。@future做到了。非常感谢。