XStream 动态转换列表

Question

我正在尝试实现一个通用的 XStream 阅读器来阅读我的 xml。我的 XML 具有所有相同的标记名，但具有不同的 ID。 示例：

来自 URL 1 的 XML 返回：

<rss>
    <reg id="someClass">
        <ds>bla bla</ds>
    </reg>
</rss>

来自 URL2 的 XML 返回：

<rss>
    <reg id="differentClass">
        <id> 1 </id>
        <location> etc </location>
    </reg>
    <reg id="differentClass">
        <id> 2 </id>
        <location> etc2 </location>
    </reg>
</rss>

如您所见，在我的 reg 标签开始之前，它们都是相同的，它可以是一个列表或单个值。但这到目前为止还可以。 但是，如果我用我的 reg 对象引用我的“someClass”类来实现我的 RSS 类，它工作得很好，它会转换并给我我期望的值，但是我需要使它通用，而不是为同一个结构创建 N 个类，我试图以这种方式实现我的 RSS 类：

public class RSS {
    private List<?> reg;
    public List<?> getReg() {
        return reg;
    }
    public void setReg(List<?> reg) {
        this.reg = reg;
    }
}

我的 SomeClass 课程：

public class SomeClass{
    private String ds;
    //getters and setters
}

我的不同类别：

public class DifferentClass{
    private String id, location;
    //getters and setters
}

并尝试为第一个 url 读取我的 XML，如下所示：

response = client.execute(httpPost, httpContext);
    xstream.ignoreUnknownElements();
    xstream.alias("rss", RSS.class);
    xstream.alias("reg", SomeClass.class);
    RSS rss = (RSS) xstream.fromXML(new InputStreamReader(response.getEntity().getContent()));
    Object user = rss.getReg();
    return (SomeClass) user;

对于第二个 url，而不是“SomeClass”，使用“differentClass”。但是这种方法不起作用，因为我得到以下异常：

---- Debugging information ----
cause-exception     : com.thoughtworks.xstream.mapper.CannotResolveClassException
cause-message       : ds
class               : java.util.ArrayList
required-type       : java.util.ArrayList
converter-type      : com.thoughtworks.xstream.converters.collections.CollectionConverter
path                : /rss/reg/ds
line number         : 12
class[1]            : br.com.test.RSS
converter-type[1]   : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
version             : 1.4.9
-------------------------------
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:79)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:70)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshallField(AbstractReflectionConverter.java:503)
    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:429)
    at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:281)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
    at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:70)
    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:1230)
    at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1214)
    at com.thoughtworks.xstream.XStream.fromXML(XStream.java:1085)
    at br.com.test.Test.get(Test.java:64)
Caused by: com.thoughtworks.xstream.mapper.CannotResolveClassException: ds
    at com.thoughtworks.xstream.mapper.DefaultMapper.realClass(DefaultMapper.java:81)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.DynamicProxyMapper.realClass(DynamicProxyMapper.java:55)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.PackageAliasingMapper.realClass(PackageAliasingMapper.java:88)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.ClassAliasingMapper.realClass(ClassAliasingMapper.java:79)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.ArrayMapper.realClass(ArrayMapper.java:74)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.SecurityMapper.realClass(SecurityMapper.java:71)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:30)
    at com.thoughtworks.xstream.mapper.CachingMapper.realClass(CachingMapper.java:47)
    at com.thoughtworks.xstream.core.util.HierarchicalStreams.readClassType(HierarchicalStreams.java:29)
    at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.readItem(AbstractCollectionConverter.java:72)
    at com.thoughtworks.xstream.converters.collections.CollectionConverter.addCurrentElementToCollection(CollectionConverter.java:98)
    at com.thoughtworks.xstream.converters.collections.CollectionConverter.populateCollection(CollectionConverter.java:91)
    at com.thoughtworks.xstream.converters.collections.CollectionConverter.populateCollection(CollectionConverter.java:85)
    at com.thoughtworks.xstream.converters.collections.CollectionConverter.unmarshal(CollectionConverter.java:80)
    at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
    ... 78 more

我被困在这里，是否可以使用 XStream 实现这种方法？如果是，如何？我可以在没有这个库的情况下让它工作（逐个标签读取），但是将来使用这个库会更容易。

Answer 1

错误消息显示 xstream 尝试将您的 ds 转换为 ArrayList。 告诉 xstream 它是一个字符串：

xstream.aliasType("ds", String.class);