Question

我创建了一个简单的类来创建XML文档。但是，如果在创建同名文档时多次调用该方法，则文件不会覆盖。如何让类自动覆盖同名的现有文件？

import java.io.File;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;

public class XMLCreater {
    public static void CreateXMLDoc(String name, String root, String[] elements, String[] children) throws TransformerConfigurationException {
        try {
            DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
            Document doc = docBuilder.newDocument();
            Element rootElement = doc.createElement(root);
            doc.appendChild(rootElement);

        for (int i = 0; i < elements.length; i ++) {
            Element element = doc.createElement(elements[i]);
                element.appendChild(doc.createTextNode(children[i]));
            rootElement.appendChild(element);
        }
        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        DOMSource source = new DOMSource(doc);
        File dir = new File(System.getProperty("user.dir"));
        StreamResult result =  new StreamResult(new File(dir + "\\XML\\" + name + ".xml"));
        transformer.transform(source, result);
    }
    catch(ParserConfigurationException pce){
          pce.printStackTrace();
    } catch(TransformerException tfe) {
         tfe.printStackTrace();
    }
}

}

Answer 1

我使用以下语句执行了您的代码：

public static void main (String[] args) 
{
    XMLCreater x = new XMLCreater();
    String[] s = {"A","B","C"};
    try 
    {
        x.CreateXMLDoc("k","root",s,s);
        x.CreateXMLDoc("k","root",s,s);
        x.CreateXMLDoc("fakih","root",s,s);
    }
    catch (TransformerConfigurationException exception) 
    { exception.printStackTrace(); }
}

它很好地覆盖了现有文件，没有覆盖问题，请自行检查。

Answer 2

我在这里说实话......我无法复制你的问题。当我在for循环中多次运行此程序时，它对我来说很好。在运行程序之前，您确定没有意外打开结果文件，从而将其锁定吗？

如果您担心多个线程同时运行程序，也许您可以应用synchronized块来阻止两个线程尝试编写同一个文件，如下所示： -

...

synchronized (XMLCreater.class) {
    StreamResult result = new StreamResult(new File(dir + "\\XML\\" + name + ".xml"));
    transformer.transform(source, result);
}

Java用流结果覆盖文件

2 个答案: