通过用户输入在Java中提供的特定属性获取元素

Question

I am new in Java Programming. I have an assignment where i have to get the element of specific attribute.I am using netbeans for my project. The attribute is taken from the user which will be searched in the xml file and the element of that attribute will be displayed. I have searched alot but couldn't find any solution.Please help me out. I am using XPathFactory. For example if i enter id in the input then it should display the element ie gemstone.The code doesnot show any error it compiles correctly but it doesnot show any output. Following is the code for java and my xml file.

java file

 String data;
       Scanner input = new Scanner (System.in);
       System.out.println("Enter Attribute whose Element you want to be displayed ");
       data = input.nextLine();
       System.out.println(" \n ");
       try {
    File fXmlFile = new File("stonesorg.xml");
    DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
    Document doc = dBuilder.parse(fXmlFile);
        doc.getDocumentElement().normalize();

        XPathFactory factory = XPathFactory.newInstance();
        XPath xpath = factory.newXPath();
        NodeList node;
        node = (NodeList) xpath.evaluate(data, doc, XPathConstants.NODESET);
        for (int x = 0; x < node.getLength(); x++)
        {
            System.out.print(node.item(x).getNodeName()+" ");
        }

         System.out.println(" \n "); 
       }
       catch(ParserConfigurationException | SAXException | IOException | DOMException e)
       {

       }   
    }

xml file

<gemstone id = "G1">
        <Name name= "Amethyst"> 
        <namehistory> The name comes from the Koine Greek. </namehistory>
        <namemeaning> Intoxicate </namemeaning>
        </Name>
        <identification> 
        <color> Violet  </color>
        <composition> Quartz,Silica (silicon dioxide, SiO2)</composition>
        <mohsScale> 7–lower in impure varieties</mohsScale>
        <crystalSystem> Trigonal</crystalSystem>
        <category> Silicate mineral </category>
        </identification>
        <history>It is from Magaliesburg, South Africa.The Greeks believed amethyst gems could prevent intoxication, while medieval European soldiers wore amethyst amulets as protection in battle in the belief that amethysts heal people and keep them cool-headed.</history>
        <geographicaldistribution>
            <country>Brazil</country>
            <country>Russia</country>
            <country>South Korea</country>
            <country>Colorado</country>
            <country>Texas</country>
            <country>Pennsylvania</country>
            <country>Ontario</country>
        </geographicaldistribution>
        <birthstone>  Birthstone for February   </birthstone>
        <properties>
            <meltingpoint> 
                            <celsius> 1650±75 °C </celsius>
                            <fahrenheit>3002 ±167°F </fahrenheit>
            </meltingpoint>
            <solubility> Insoluble in common solvents </solubility>
            <gravity> 2.65 constant </gravity>
        </properties>
    </gemstone>

Answer 1

First of all: never suppress exceptions (if you did not shrink code sample). At least put e.printStackTrace(); there

catch(ParserConfigurationException | SAXException | IOException | DOMException e)
   {
     e.printStackTrace();
   }   

Second: your code must not compile - one exception is missing in catch - XPathException

Third (and main): after adding XPathException your code is working, but you need to be aware what XPath you enter as input. (please read docs and tutorials about XPath).

It is not that simple as just a Node name you want to get. As long as you run it from top Document - yes you can enter gemstone - because it is a root element, but for other nodes you have to provide valid XPath - otherwise you will get nothing.

BTW try to make your print statement a little more informative for debugging like:

System.out.println(node.item(x).getNodeName()+" " + node.item(x).getTextContent());

Later you can make more nice...

So, try some examples:

• gemstone
• gemstone/Name/@name
• gemstone/geographicaldistribution/*
• gemstone/geographicaldistribution/country
• //country[3]
• //country[text()='Texas']