java - 抛出 SAXException

Question

学习使用 Java 进行 xml 解析，并且正在编写一个测试程序来尝试各种东西。所有测试 System.out.println() 都是我在控制台中所期望的，除了 childElement 返回 [name: null] 和 childElement.getNodeValue() 返回 null 而不是 [name: "Branch Name"] 和 "分行名称”分别。

为了纠正这个问题，我开始调整，当然进一步破坏了程序。现在，当我尝试运行时，我抛出一个 SAXException (我已经用注释标记了我将其范围缩小到的行，尽管我不太清楚 SAXException 的含义等)似乎无法让她回到以前的状态。

这是现在的代码:

package uploaders;

import javax.swing.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import org.xml.sax.SAXException;
import java.awt.EventQueue;
import java.io.*;

public class Test {
    public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException { 
        JFileChooser chooser = new JFileChooser();
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        StringBuilder xmlStringBuilder = new StringBuilder();
        String appendage = "<?xml version=\"1.0\"?><branch0><name>Branch Name</name></branch0>";
        ByteArrayInputStream input = new ByteArrayInputStream(xmlStringBuilder.toString().getBytes("UTF-8"));

        chooser.setCurrentDirectory(new File("."));
        chooser.setMultiSelectionEnabled(false);
        chooser.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);

        int result = chooser.showOpenDialog(null);

        if (result == JFileChooser.APPROVE_OPTION) { 
            System.out.println("Test Results:");
            System.out.println();
            System.out.println(chooser.getSelectedFile().getPath()); 

            Document doc = builder.parse(input); //originally org.w3c.dom.Document...this line is where SAXException is thrown.
            Element root = doc.getDocumentElement(); 
            NodeList children = root.getChildNodes();

            System.out.println(root.getTagName());
            xmlStringBuilder.append(appendage); //forgot to move this up too (thanks @Vihar)

            for (int i = 0; i < children.getLength(); i++) {
                Node child = children.item(i);
                if (child instanceof Element) { 
                    Element childElement = (Element) child; 
                    System.out.println(childElement.getTagName());
                    System.out.println(childElement.getNodeValue());
                    System.out.println(childElement); }
            }
        }   
    }
}

非常感谢有关 SAXException 的任何帮助，之后我可能仍然需要弄清楚为什么“name”元素返回“null”，但首先是:)。

已更新 注释中显示了导致 SAXException 的原因。但是控制台仍然显示此内容:

Test Results:

/Users/.../Documents/java/Test/./bin
branch0
name
null           //I'm expecting "Branch Name"
[name: null]   //and "[name: Branch Name]"

终于

childElement.getNodeValue() //needed + .toString() to work or:
childElement.getNodeValue().toString()

或

childElement.getTextContent()

Answer 1

问题就出在这里

ByteArrayInputStream input = new ByteArrayInputStream(xmlStringBuilder.toString().getBytes("UTF-8"));

您刚刚创建了一个 StringBuilder(xmlStringBuilder) 的空对象，并希望对其进行解析，因此编译器会抛出 SAXParseException

但你确实需要这样做

ByteArrayInputStream input = new ByteArrayInputStream(appendage.toString().getBytes("UTF-8"));

当你appendage字符串包含实际的xml信息

或者这样做

xmlStringBuilder.append(appendage);   //I have just changed the sequence of these lines in your code
ByteArrayInputStream input = new ByteArrayInputStream(xmlStringBuilder.toString().getBytes("UTF-8"));
Document doc = builder.parse(input); 

希望这有帮助!

祝你好运!