怎么做“ builder.parse（存储在这个罐子里的xml文件）”？

Question

I am trying to use a file object, with the path of a XML file inside of the current jar file, which is running, in builder.parse(not the absolute path to the xml file);

DocumentBuilder builder = dbf.newDocumentBuilder();

Document doc = builder.parse("resources/userConfig.xml");

The code works in eclipse but doesn't in a exported jar file. When i run the exported jar it can't find the XML in C:\\Users...

Answer 1

For your case you need the one but last method below, that takes an InputStream. The last method is added as an example for your case with the file in a jar in the classpath. You may want to do the exceptionhandling differently.

public class XMLLib {

    public static DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();

    public static Document readXML(File file) {
        try {
            final DocumentBuilder builder = builderFactory.newDocumentBuilder();
            return builder.parse(file);
        } catch (ParserConfigurationException ex) {
           return null;
        } catch (SAXException | IOException ex) {
           return null;
        }
    }

    public static Document readXML(InputStream is) {
        try {
            final DocumentBuilder builder = builderFactory.newDocumentBuilder();
            return builder.parse(is);
        } catch (ParserConfigurationException ex) {
             return null;
        } catch (SAXException | IOException ex) {
            return null;
        }
    }

    //example call:
    public static Document getDocumentResource(String resourcepath){
        try (InputStream is = XMLLib.class.getResourceAsStream(resourcepath)){
             return readXML(is); 
         } catch (IOException ex) {}
         return null;
    }
}

Some more explaination: In the Eclipse environment the xml-file is extracted, so you can access it directly as a File(as it is a "File"). Now with everything in a jar the xml doesn't exist as a "File" anymore so you have to extract it from the jar file. The classloader is able to do so via getResourceAsStream - just like it can read other resources and classes. So in essence, what this is doing is loading the xml like java loads a class. For that to work, the resourcepath must be given with respect to the classpath. Only the InputStream version above will work(or some other aproach eg using Path and Filesystem)

Usualy if you have a resource in "resources/userConfig.xml" the path is simple "/userConfig.xml". (but that depends on how the project is assembled)

I can only guess(depends on how the project is assembled) in your case you need:

Document document = XMLLib.getDocumentResource("/userConfig.xml");

Important: the InputStream Version works with the file in the jar and with the file extracted(this is allways ) - as long as it can be found by the classloader.