XML节点值的快速替换

Question

我有一堆XML文档，其中包含我需要用假数据替换的个人信息。Person节点包含以下元素：

• UUID-必填项，不应触及。
• 名字-可选
• LastName-可选
• 地址-可选
• 个人身份-必需

一个人可能会出现很多次，在这种情况下应该使用相同的假数据，即如果两个person节点具有相同的personID，那么它们都应该接收到相同的假ID。

我已经实现了一些Java代码，这些代码从XML字符串构建一个DOM树，并在将其写回字符串之前替换节点。这工作很好，但由于我有这么多的文档，我想知道是否有一个更快的方法。也许通过正则表达式或XSLT什么的？

下面是一个示例文档：

<ADocument>
  <Stuff>
    ...
  </Stuff>
  <OtherStuff>
    ...
  </OtherStuff>
  <Person>
    <uuid>11111111-1111-1111-1111-111111111111</uuid>
    <firstName>Some</firstName>
    <lastName>Person</lastName>
    <personID>111111111111</personID>
  </Person>
  <Person>
    <uuid>22222222-2222-2222-2222-222222222222</uuid>
    <firstName>Another Person</firstName>
    <address>Main St. 2</address>
    <personID>222222222222</personID>
  </Person>
  <Person>
    <uuid>33333333-3333-3333-3333-333333333333</uuid>
    <firstName>Some</firstName>
    <lastName>Person</lastName>
    <personID>111111111111</personID>
  </Person>
  <MoreStuff>
    ...
  </MoreStuff>
</ADocument>

这是我当前的实现：

public String replaceWithFalseData(String xmlInstance) {
    Document dom = toDOM(xmlInstance);

    XPathExpression xPathExpression = XPathExpressionFactory.createXPathExpression("//Person");
    List<Node> nodeList = xPathExpression.evaluateAsNodeList(dom);

    for(Node personNode : nodeList) {
        Map<String, Node> childNodes = getChildNodes(personNode);
        String personID = childNodes.get("personID").getTextContent();
        // Retrieve a cached fake person using the ID, or create a new one if none exists.
        Person fakePerson = getFakePerson(personID);

        setIfExists(childNodes.get("firstName"), fakePerson.getFirstName());
        setIfExists(childNodes.get("lastName"), fakePerson.getLastName());
        setIfExists(childNodes.get("address"), fakePerson.getAddress());
        setIfExists(childNodes.get("personID"), fakePerson.getPersonID());
    }

    return toString(dom);
}

public Map<String, Node> getChildNodes(Node parent) {
    Map<String, Node> childNodes = new HashMap<String, Node>();
    for(Node child = parent.getFirstChild(); child != null; child = child.getNextSibling()) {
        if(child.getLocalName() != null) {
            childNodes.put(child.getLocalName(), child);
        }
    }
    return childNodes;
}

public void setIfExists(Node node, String value) {
    if(node != null) {
        node.setTextContent(value);
    }
}

Answer 1

我不确定XSLT是否能在这方面有所帮助。也许我对XSLT的了解还不够深刻，但是XSLT可以根据现有XML的数据创建一个新的XML结构。在这里，您似乎想要做相反的事情：维护相同的结构，但基于动态值更新数据。您可能很难创建这样的XSLT。优化可以依赖于相当多的参数：每个XML的Person元素的数量、XML中相等的Person的数量、要处理的XML的数量……如果您处理的是大文件，您可能希望切换到SAX实现以优化内存消耗。如果您在同一个XML中处理大量相同的personid，您可以在假数据后面构建一些缓存结构，用于替换这些缓存结构，以减少DOM上的点击量（您可以直接用缓存的节点替换节点，并用原始的uuid覆盖uuid）。如果您有许多包含相似PersonIDs的小文件，那么如果可以在多个XML文件上使用相同的假数据，那么您可能希望使用交叉XML缓存。

此外，我相信您可以删除PersonID上的“set ifexists”，因为它被声明为强制字段。

Answer 2

您正在使用基于DOM的API。XML流API(StAX)可以实现更快的替换，在许多情况下，它的性能优于基于DOM的API：StAX对DOM

DOM API比StAX占用更多的内存，这会降低性能，但比StAX API更容易使用。

您的示例的工作解决方案-在150 MB xml文件上测试，10秒内替换：

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.xml.stream.XMLEventFactory;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLEventWriter;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLOutputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.events.XMLEvent;


public class ReplaceXmlWithFakeUser
{
  public static void main(String[] args) throws XMLStreamException, IOException
  {
    XMLInputFactory inFactory = XMLInputFactory.newInstance();
    XMLEventReader eventReader = inFactory.createXMLEventReader(new BufferedInputStream(new FileInputStream("c:\\temp\\persons.xml")));
    XMLOutputFactory factory = XMLOutputFactory.newInstance();
    XMLEventWriter writer = factory.createXMLEventWriter(new BufferedOutputStream(new FileOutputStream("c:\\temp\\fakePersons.xml")));
    XMLEventFactory eventFactory = XMLEventFactory.newInstance();
    while (eventReader.hasNext())
    {
      XMLEvent event = eventReader.nextEvent();

      if (event.getEventType() == XMLEvent.START_ELEMENT &&
        event.asStartElement().getName().toString().equals("Person"))
      {
        //write Person startElement:
        writer.add(event);


        /*
        STEP 1:
        personId is at the end of Person element. Cannot overwrite firstName and address element with fake data yet. Must call getFakePerson() first.
        Iterate till you read Person END element and just remember all events within person element which we will overwrite with fake data in step 2.
         */
        Person fakePerson=null;

        List<XMLEvent> eventsWithinPersonElement = new ArrayList<XMLEvent>();

        event = eventReader.nextEvent();
        while(!(event.getEventType() == XMLEvent.END_ELEMENT && event.asEndElement().getName().toString().equals("Person")))
        {

          eventsWithinPersonElement.add(event);

          if(event.getEventType() == XMLEvent.START_ELEMENT &&
              event.asStartElement().getName().toString().equals("personID"))
          {
            XMLEvent personIDContentEvent = eventReader.nextEvent();

            String personId = personIDContentEvent.asCharacters().toString();
            fakePerson = getFakePerson(personId);

            eventsWithinPersonElement.add(personIDContentEvent);
          }

          event = eventReader.nextEvent();
        }
        XMLEvent personEndElement=event;


        //STEP 2:
        for (Iterator<XMLEvent> eventWithinPersonElementIterator = eventsWithinPersonElement.iterator(); eventWithinPersonElementIterator.hasNext(); )
        {
          XMLEvent eventWithinPersonElement = eventWithinPersonElementIterator.next();

          writer.add(eventWithinPersonElement);

          if(eventWithinPersonElement.getEventType() == XMLEvent.START_ELEMENT &&
              eventWithinPersonElement.asStartElement().getName().toString().equals("personID"))
          {
            writer.add(eventFactory.createCharacters(fakePerson.personId));

            //skip personId event
            eventWithinPersonElementIterator.next();
          }
          if(eventWithinPersonElement.getEventType() == XMLEvent.START_ELEMENT &&
              eventWithinPersonElement.asStartElement().getName().toString().equals("firstName"))
          {
            writer.add(eventFactory.createCharacters(fakePerson.firstName));

            //skip real firstName
            eventWithinPersonElementIterator.next();
          }
          if(eventWithinPersonElement.getEventType() == XMLEvent.START_ELEMENT &&
              eventWithinPersonElement.asStartElement().getName().toString().equals("lastName"))
          {
            writer.add(eventFactory.createCharacters(fakePerson.lastName));

            //skip real firstName
            eventWithinPersonElementIterator.next();
          }
          else if(eventWithinPersonElement.getEventType() == XMLEvent.START_ELEMENT &&
              eventWithinPersonElement.asStartElement().getName().toString().equals("address"))
          {
            writer.add(eventFactory.createCharacters(fakePerson.address));

            //skip real address
            eventWithinPersonElementIterator.next();

          }
        }

        writer.add(personEndElement);
      }
      else
      {
        writer.add(event);
      }
    }
    writer.close();
  }

  private static Person getFakePerson(String personId)
  {
    //create simple fake user...

    Person fakePerson = new Person();
    fakePerson.personId = personId;
    fakePerson.firstName = "fake first name: " + Math.random();
    fakePerson.lastName = "fake last name: " + Math.random();
    fakePerson.address = "fake address: " + Math.random();

    return fakePerson;
  }

  static class Person
  {
    String personId;
    String firstName;
    String lastName;
    String address;

  }
}

使用persons.xml作为输入：

<ADocument>
    <Stuff>
        <StuffA></StuffA>
    </Stuff>
    <OtherStuff>
        <OtherStuff>
            <ABC>yada yada</ABC>
        </OtherStuff>
    </OtherStuff>

    <Person>
        <uuid>11111111-1111-1111-1111-111111111111</uuid>
        <firstName>Some</firstName>
        <lastName>Person</lastName>
        <personID>111111111111</personID>
    </Person>
    <Person>
        <uuid>22222222-2222-2222-2222-222222222222</uuid>
        <firstName>Another Person</firstName>
        <address>Main St. 2</address>
        <personID>222222222222</personID>
    </Person>
    <Person>
        <uuid>33333333-3333-3333-3333-333333333333</uuid>
        <firstName>Some</firstName>
        <lastName>Person</lastName>
        <personID>111111111111</personID>
    </Person>

    <MoreStuff>
        <foo></foo>
        <foo>fooo</foo>
        <foo><bar></bar></foo>
        <foo>
            <bar></bar>
            <bar/>
            <bar>bb</bar>
        </foo>
        <bar/>
    </MoreStuff>

</ADocument>

生成此fakepers.xml结果：

<?xml version="1.0" encoding="UTF-8"?><ADocument>
    <Stuff>
        <StuffA></StuffA>
    </Stuff>
    <OtherStuff>
        <OtherStuff>
            <ABC>yada yada</ABC>
        </OtherStuff>
    </OtherStuff>

    <Person>
        <uuid>11111111-1111-1111-1111-111111111111</uuid>
        <firstName>fake first name: 0.9518514637129984</firstName>
        <lastName>fake last name: 0.3495378044884426</lastName>
        <personID>111111111111</personID>
    </Person>
    <Person>
        <uuid>22222222-2222-2222-2222-222222222222</uuid>
        <firstName>fake first name: 0.8945739434355868</firstName>
        <address>fake address: 0.40784763231471777</address>
        <personID>222222222222</personID>
    </Person>
    <Person>
        <uuid>33333333-3333-3333-3333-333333333333</uuid>
        <firstName>fake first name: 0.7863207851479257</firstName>
        <lastName>fake last name: 0.09918620445731652</lastName>
        <personID>111111111111</personID>
    </Person>

    <MoreStuff>
        <foo></foo>
        <foo>fooo</foo>
        <foo><bar></bar></foo>
        <foo>
            <bar></bar>
            <bar></bar>
            <bar>bb</bar>
        </foo>
        <bar></bar>
    </MoreStuff>

</ADocument>