Question

我有这个XML文件：

<?xml version="1.0" encoding="UTF-8"?>

<music>
  <artist name="Eminem">
    <album title="Recovery" year="2010" art="cover.png">
      <song title="Cold Wind Blows" />
      <song title="Talkin' 2 Myself"/>
      <song title="On Fire"/>
    </album>
  </artist>
</music>

我用这段代码解析它：

// Get child elements of root
NodeList artistList = document.getElementsByTagName("artist");

for(int i = 0; i < artistList.getLength(); i++)
{
    Node artistNode = artistList.item(i);

    if(artistNode.getNodeType() == Node.ELEMENT_NODE)
    {
        // Album list
        NodeList albumList = artistNode.getChildNodes();

        // Get artist name
        String artistName = artistNode.getAttributes().getNamedItem("name").getNodeValue();

        for(int j = 0; j < albumList.getLength(); j++)
        {
            Node albumNode = albumList.item(j).getNextSibling();

            String albumTitle = albumNode.getAttributes().getNamedItem("title").getNodeValue();
            String albumYear = albumNode.getAttributes().getNamedItem("year").getNodeValue();
            String albumArt = albumNode.getAttributes().getNamedItem("art").getNodeValue();

            System.out.println(artistName+albumTitle+albumYear+albumArt);
        }
    }
}

这打印出属性值就好了。但是，当j为1时，我会在此行中获得NullPointerException：

String albumTitle = albumNode.getAttributes().getNamedItem("title").getNodeValue();

我做错了什么？我应该用更少的for循环以不同的方式解析它吗？我想我需要另一个循环来获取歌曲信息。

任何帮助将不胜感激！

完整堆栈跟踪：

EminemRecovery2010cover.png
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.NullPointerException
    at songlibrary.SongList.buildSongList(SongList.java:69)
    at app.Main.main(Main.java:37)
    ... 11 more
Exception running application app.Main

解析XML文件时出现NullPointerException

0 个答案: