java - XStream 并使用 'ToAttributedValueConverter' 表示两个相似但不同的 XML 字段

Question

在我的 XML 文件中，有这样的行；

    <text id="name">Bu ilk rule</text>
    <text id="bundleName">Rule.behavior</text>

所以我的 Text 类是这样的:

@XStreamConverter(value = ToAttributedValueConverter.class, strings = {"value"})
@XStreamAlias("text")
public class Text {

    @XStreamAsAttribute
    String id = "unset";
    String value = "0";
}

而且它有效。但今天我在 XML 中得到了这个:

        <text id="targetAttribute">game.devices.touches.touch1.y</text>
        <text id="RHS">
          <expression>
            <string>acos(x)</string>
          </expression>
        </text>

而且它不起作用。如果我删除 @XStreamConverter我得到这样的输出:

        <text id="targetAttribute"/>
        <text id="RHS">
          <expression>
            <string>acos(x)</string>
          </expression>
        </text>

解决这个问题的方法是什么？

编辑:

在马蒂亚斯回答之后，我能得到的最接近所需的格式是:

        <text id="RHS">
          <expression>
            <string>acos(x)</string>
          </expression>
        </text>

但是这个方法失败了，它开始不显示“value”字段:

        <text id="name"/>
        <text id="bundleName"/>
        <text id="targetAttribute"/>

对于这个类:

@XStreamAlias("text")

class Test {

    @XStreamAsAttribute
    String id = "unset";
    String value = "0";
    myString string = new myString();
    Expression expression = new Expression();

}

另外，我是这样阅读的，所以这样做时它必须有效:

String xml1 = readFile("C:\\1.xml");
Actor actorNew = (Actor) xstream.fromXML(xml1);

String xmlNew = xstream.toXML(actorNew);
System.out.println(xmlNew);

编辑2:

<string> 的 myString 类在 XML 中:

@XStreamConverter(value = ToAttributedValueConverter.class, strings = {"value"})
public class myString {

    @XStreamAlias("string")
    String value = "";

}

这是我正在尝试读取的 XML 的缩小 View :

<behaviors>
        <behavior id="id384781" class="ChangeAttributeAction" enabled="true">
          <attributes>
            <text id="name">Change Attribute</text>
            <text id="bundleName">ChangeAttribute.behavior</text>
            <text id="targetAttribute">game.devices.touches.touch1.y</text>
            <text id="RHS">
              <expression>
                <string>acos(x)</string>
              </expression>
            </text>
          </attributes>
        </behavior>
</behaviors>

一切正常，直到 id =“RHS”的文本

编辑3:

我在自定义转换器上尝试了类似的方法，但没有成功:

@Override
public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
    Test test = new Test();
    test.expression = new Expression();
    test.expression.string = new myString();
    test.value = reader.getValue();
    test.id = reader.getAttribute("id");
    reader.moveDown();
    reader.moveDown();
    test.expression.string.value = reader.getValue();
    return test;
}

编辑4

WOOOOOOOOOOOOOOOOOOO我终于明白了!

这是我的做法:

class ValueConverter implements Converter {

    @Override
    public boolean canConvert(Class type) {
        return Test.class.isAssignableFrom(type);
    }

    @Override
    public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
        Test src = (Test) source;
        writer.addAttribute("id", src.id);
        writer.setValue(src.value);

        if (src.expression.string.value.length() > 0) {
            writer.startNode("expression");
            writer.startNode("string");
            writer.setValue(src.expression.string.value);
            writer.endNode();
        }

    }

    @Override
    public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
        Test test = new Test();
        test.id = reader.getAttribute("id");
        test.value = reader.getValue();
        if (reader.hasMoreChildren()) {
            reader.moveDown();
            reader.moveDown();
            test.expression.string.value = reader.getValue();

        }
        return test;
    }

}

Answer 1

嗯，您显示的代码无法生成此 XML。我猜想在你的真实代码中的某个地方，有一些继承(扩展你的测试类的类表达式)正在产生这个结果。似乎 ToAttributedValueConverter 并不真正适用于派生类，并且在那里被忽略。

如果您想要将更复杂的对象结构映射到非常具体的 XML 表示形式，则应该使用转换器。如果有疑问，您始终可以创建一个自定义转换器来处理编码/解码。对于这些转换器，您可以轻松定义应将它们用于哪些类(请参阅 canConvert(Class) 方法。

我为您做了一段非常相似的代码:

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;

@XStreamAlias("text")
class Test {

  String id = "unset";
  String value = "0";
}

@XStreamAlias("expression")
class Expression extends Test {
  Expression() {
    value = "acos(x)";
  }
}

class ValueConverter implements Converter {

  @Override
  public boolean canConvert(Class type) {
    return Test.class.isAssignableFrom(type);
  }

  @Override
  public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
    Test src = (Test)source;
    writer.addAttribute("id", src.id);
    writer.setValue(src.value);
  }

  @Override
  public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
    Test test = new Test();
    test.value = reader.getValue();
    test.id = reader.getAttribute("id");
    return test;
  }

}

public class Example {
  public static void main(String[] args) {
    XStream xStream = new XStream();
    xStream.autodetectAnnotations(true);
    System.out.println("BEFORE setting a converter:");
    System.out.println(xStream.toXML(new Test()));
    System.out.println(xStream.toXML(new Expression()));
    xStream.registerConverter(new ValueConverter());
    System.out.println("\nAFTER setting a converter:");
    System.out.println(xStream.toXML(new Test()));
    System.out.println(xStream.toXML(new Expression()));
  }
}

运行此命令，您将得到以下输出:

<text>
  <id>unset</id>
  <value>0</value>
</text>
<expression>
  <id>unset</id>
  <value>acos(x)</value>
</expression>

AFTER setting a converter:
<text id="unset">0</text>
<expression id="unset">acos(x)</expression>