java - 尝试更改空字符串的反序列化方式时发生 ConvertException : Element annotation required for field

Question

我正在使用 Java 开发一个字典式应用程序，并且使用 Simple 框架进行序列化。它包含一个字符串数组列表，我遇到的唯一问题是 Simple 会序列化/反序列化这些字符串并将任何空值更改为 null。我从this question了解到您需要使用转换器。我按照该页面上的描述添加了 Sand 在他的答案中编写的类(需要进行“new AnnotationStrategy()”更改)，现在这就是我遇到问题的主类的样子(与大量的 get/set 方法被删除):

    public class Item  {

    @ElementList(name = "itemContents")
    @Convert(SimpleXMLStringConverter.class)
    private ArrayList<String> values;

    public Item()
    {
    }
}

每当我尝试将类写入 XML 文件时，都会收到此错误:

org.simpleframework.xml.convert.ConvertException: Element annotation required for field 'values' private java.util.ArrayList main.LangComp.Item.values
    at org.simpleframework.xml.convert.ConverterScanner.getConvert(ConverterScanner.java:147)
    at org.simpleframework.xml.convert.ConverterScanner.getConvert(ConverterScanner.java:121)
    at org.simpleframework.xml.convert.ConverterScanner.getConverter(ConverterScanner.java:100)
    at org.simpleframework.xml.convert.AnnotationStrategy.write(AnnotationStrategy.java:175)
    at org.simpleframework.xml.convert.AnnotationStrategy.write(AnnotationStrategy.java:155)
    at org.simpleframework.xml.core.Source.setOverride(Source.java:394)
    at org.simpleframework.xml.core.Factory.setOverride(Factory.java:170)
    at org.simpleframework.xml.core.Composite.isOverridden(Composite.java:1387)
    at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1309)
    at org.simpleframework.xml.core.Composite.writeUnion(Composite.java:1194)
    at org.simpleframework.xml.core.Composite.writeElements(Composite.java:1165)
    at org.simpleframework.xml.core.Composite.writeSection(Composite.java:1071)
    at org.simpleframework.xml.core.Composite.write(Composite.java:1042)
    at org.simpleframework.xml.core.Composite.write(Composite.java:1019)
    at org.simpleframework.xml.core.Traverser.write(Traverser.java:236)
    at org.simpleframework.xml.core.CompositeList.write(CompositeList.java:248)
    at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1331)
    at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1314)
    at org.simpleframework.xml.core.Composite.writeUnion(Composite.java:1194)
    at org.simpleframework.xml.core.Composite.writeElements(Composite.java:1165)
    at org.simpleframework.xml.core.Composite.writeSection(Composite.java:1071)
    at org.simpleframework.xml.core.Composite.write(Composite.java:1042)
    at org.simpleframework.xml.core.Composite.write(Composite.java:1019)
    at org.simpleframework.xml.core.Traverser.write(Traverser.java:236)
    at org.simpleframework.xml.core.Traverser.write(Traverser.java:208)
    at org.simpleframework.xml.core.Traverser.write(Traverser.java:186)
    at org.simpleframework.xml.core.Persister.write(Persister.java:1187)
    at org.simpleframework.xml.core.Persister.write(Persister.java:1169)
    at org.simpleframework.xml.core.Persister.write(Persister.java:1147)
    at org.simpleframework.xml.core.Persister.write(Persister.java:1266)
    at org.simpleframework.xml.core.Persister.write(Persister.java:1248)
    at org.simpleframework.xml.core.Persister.write(Persister.java:1229)
    at org.simpleframework.xml.core.Persister.write(Persister.java:1208)
    at main.IO.FileHandler.WriteXML(FileHandler.java:32)
    at main.UI.MainUI.formWindowClosing(MainUI.java:108)
    at main.UI.MainUI.access$000(MainUI.java:16)
    at main.UI.MainUI$1.windowClosing(MainUI.java:76)
    at java.awt.Window.processWindowEvent(Window.java:2045)
    at javax.swing.JFrame.processWindowEvent(JFrame.java:296)
    at java.awt.Window.processEvent(Window.java:2003)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Window.dispatchEventImpl(Window.java:2713)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:707)
    at java.awt.EventQueue.access$000(EventQueue.java:101)
    at java.awt.EventQueue$3.run(EventQueue.java:666)
    at java.awt.EventQueue$3.run(EventQueue.java:664)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:680)
    at java.awt.EventQueue$4.run(EventQueue.java:678)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:677)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

我之前能够让这个程序工作，唯一的问题是它会把空字符串变成空，这是我需要避免的。我不知道是什么原因导致了问题或如何解决它。是因为我从链接的问题中获得的转换器类适用于字符串，而不是 ArrayList，还是因为 XML 节点是字符串而不是列表而无关紧要？当它说“字段需要元素注释”时，我无法理解它想要什么注释。

Answer 1

抛出错误消息是因为我使用了@ElementList，并且此过程需要@Element。我找到了一种让它与 ArrayLists 一起工作的方法，因为我放弃了尝试让它在一个实例中工作，只是希望转换器适用于一切。我不知道这是否是一个好方法，但它确实有效。我只是按照here描述的步骤进行操作创建一个RegistryStrategy，我没有将转换器绑定(bind)到我的类(它不会接受)，而是将它绑定(bind)到String.class；换句话说，序列化过程不关心它是否存储在复杂的类中，ArrayList等，如果它是一个String，那么如果它读入为null，它将被设置为“”。