Question

我一直在研究这个问题已经有一段时间了，无法弄明白。有一个给定的“xml”文件需要解析并显示在屏幕上：

<office>

<name>joe</name>
<surname>smith</surname>
<name>bob</name>
<surname>black</surname>

.....
</office>

我在网上发现了一些很棒的代码示例，但它们似乎不适用于未正确设置的xml文件，所以如果我添加一个标记，我可以让我的代码工作，但问题是我无法对“xml”文件进行任何更改。

我在这里找到的其他人的代码已被修改。

这是我的mods代码：

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Scanner;

import org.w3c.dom.*;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.ParserConfigurationException;

import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException; 

public class ReadAndPrintXMLFile{

public static void main (String argv []) throws ParserConfigurationException, SAXException, IOException{



try {

        DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
        Document doc = docBuilder.parse (new File("office.xml"));

        // normalize text representation
        doc.getDocumentElement ().normalize ();
        System.out.println ("Root element of the doc is " + 
        doc.getDocumentElement().getNodeName() + "\n");

        //counts how many times <name> is found in the file
        //then the number is used in the for loop below             
        NodeList listOfTerms = doc.getElementsByTagName("name");

        int totalTerms = listOfTerms.getLength();
        System.out.println("Total no of terms : " + totalTerms + "\n");



        for(int s= 0; s<listOfTerms.getLength() ; s++){


            Node firstTermNode = listOfTerms.item(s);
            if(firstTermNode.getNodeType() == Node.ELEMENT_NODE){


                Element firstTermElement = (Element)firstTermNode;

                //-------
                NodeList firstWordList = firstTermElement.getElementsByTagName("name");
                Element firstWordElement = (Element)firstWordList.item(0);

                NodeList textWordList = firstWordElement.getChildNodes();
                System.out.println("Name : " + 
                       ((Node)textWordList.item(0)).getNodeValue().trim());

                //-------
                NodeList defList = firstTermElement.getElementsByTagName("surname");
                Element defElement = (Element)defList.item(0);

                NodeList textDefList = defElement.getChildNodes();
                System.out.println("Surname : " + 
                       ((Node)textDefList.item(0)).getNodeValue().trim());



            }//end of if clause


        }//end of for loop with s var


    }catch (SAXParseException err) {
    System.out.println ("** Parsing error" + ", line " 
         + err.getLineNumber () + ", uri " + err.getSystemId ());
    System.out.println(" " + err.getMessage ());

    }catch (SAXException e) {
    Exception x = e.getException ();
    ((x == null) ? e : x).printStackTrace ();

    }catch (Throwable t) {
    t.printStackTrace ();
    }
    //System.exit (0);


}//end of main
}

我得到的错误信息是：

java.lang.NullPointerException
    at Data.main(Data.java:45) //maybe a different line in the code for you.

如果我将文档的根用于计数器，它会打印一次结果，因为某些原因getChildNodes（）无法正常工作。

Answer 1

我注意到你做了两次.getElementsByTagName（“name”）。你期待＆lt; name＆gt; ＆lt; name＆gt;中的标签？如果没有那么那很可能是你的错误的原因，因为第二次，它会返回一个空列表，当你尝试引用firstWordElement时会导致NullPointerException

您无法从'name'列表中获取'surname'，这是您在for循环中所做的。在不同的步骤中获取它们，以便获取“名称”元素：

    NodeList listOfTerms = doc.getElementsByTagName("name");
    int totalTerms = listOfTerms.getLength();
    System.out.println("Total no of terms : " + totalTerms + "\n");
    for(int s= 0; s<listOfTerms.getLength() ; s++){
        Node firstTermNode = listOfTerms.item(s);
        if(firstTermNode.getNodeType() == Node.ELEMENT_NODE){
            Element firstTermElement = (Element)firstTermNode;
            System.out.println(firstTermElement.getTextContent());
        }//end of if clause
    }//end of for loop with s var

然后获取姓氏，只需改变标记名

listOfTerms = doc.getElementsByTagName("surname");
totalTerms = listOfTerms.getLength();
System.out.println("Total no of terms : " + totalTerms + "\n");
for(int s= 0; s<listOfTerms.getLength() ; s++){
    Node firstTermNode = listOfTerms.item(s);
    if(firstTermNode.getNodeType() == Node.ELEMENT_NODE){
        Element firstTermElement = (Element)firstTermNode;
        System.out.println(firstTermElement.getTextContent());
    }//end of if clause
}//end of for loop with s var

希望有所帮助。

用Java解析fake-xml文件

1 个答案: