我目前不知道问题出在哪里。第一次使用 xml,我在将 ArrayList 放入 xml 文件并从中取出它时遇到了一些问题。
我发现了这个,我尝试以同样的方式做:如何使用 XStream 将对象列表转换为 XML 文档 https://stackoverflow.com/questions/4077071/how-to-convert-list-of-object-to-xml-doc-using-xstream
但不幸的是我失败了。
到目前为止我所拥有的:
保存ArrayList的类:
public class ElbowList{
private ArrayList<Elbow> elbows = new ArrayList<>();
public ElbowList(){
elbows = new ArrayList<Elbow>();
}
public void setElbows(ArrayList<Elbow> elbows){
this.elbows.clear();
this.elbows = elbows;
}
public ArrayList<Elbow> getElbows() {
return elbows;
}
public void add(Elbow elbow){
elbows.add(elbow);
}
}
保存到 XML:
MainFrame mainFrame = (MainFrame) SwingUtilities.getWindowAncestor(SetupPanel.this);
ElbowList elbowList = (ElbowList) mainFrame.getObjects().get(2); //get ElbowList object
XStream xstream = new XStream();
xstream.alias("elbow", Elbow.class);
xstream.alias("elbows", ElbowList.class);
xstream.addImplicitCollection(ElbowList.class, "elbows", Elbow.class);
String xml = xstream.toXML(elbowList.getElbows());
System.out.println(xml);
try {
PrintWriter out = new PrintWriter("Save.xml");
out.println(xml);
out.close();
} catch (FileNotFoundException ex) {
Logger.getLogger(SetupPanel.class.getName()).log(Level.SEVERE, null, ex);
}
上面那个实际上似乎工作正常。
加载 XML 文件,我在此处收到异常调用:
try {
XStream xstream = new XStream();
FileReader reader = new FileReader("Save.xml");
MainFrame mainFrame = (MainFrame) SwingUtilities.getWindowAncestor(SetupPanel.this);
ElbowList elbowList = (ElbowList) mainFrame.getObjects().get(2);
elbowList.setElbows((ArrayList<Elbow>) xstream.fromXML(reader));//exception occurs here
SpacePanel spacePanel = (SpacePanel) mainFrame.getObjects().get(1);
spacePanel.repaint();
} catch (IOException ex) {
Logger.getLogger(SetupPanel.class.getName()).log(Level.SEVERE, null, ex);
}
我得到一个例外:
Exception in thread "AWT-EventQueue-0" com.thoughtworks.xstream.converters.ConversionException: elbow : elbow
---- Debugging information ----
message : elbow
cause-exception : com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message : elbow
class : java.util.ArrayList
required-type : java.util.ArrayList
converter-type : com.thoughtworks.xstream.converters.collections.CollectionConverter
path : /list/elbow
line number : 2
version : 1.4.7
-------------------------------
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:79)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:79)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1185)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1169)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:1040)
at view.SetupPanel$2.actionPerformed(SetupPanel.java:78)
(...)
我不明白为什么会出现转换异常,对我来说,如果发生异常时涉及到这一行,一切似乎都是正确的。我不知道出了什么问题,请帮忙。