同じ名前のノードをXStreamで2つの異なるクラスにデシリアライズする方法

Question

XMLファイルをデシリアライズする際に問題があります。

私のファイルは次のようである：

<mission> 
    <branch> 
     <alternative uid="0" type="ALT_MONITOR"/> 
     <alternative uid="1" type="ALT_IF" condition="i==10"/> 
    </branch> 
</mission> 

私は代替というクラスがあります。

public abtract class Alternative { 
    @XStreamAsAttribute 
    public int uid; 
    @XStreamAsAttribute 
    public String type; 
} 

このクラスは、他の二つのクラスによって拡張されます。

@XStreamAlias("alternative") 
public class AlternativeA extends Alternative { 
} 

@XStreamAlias("alternative") 
public class AlternativeB extends Alternative { 
    @XStreamAsAttribute 
    public String condition; 
} 

し、私が持っているのxStreamコンバータ：

public class AlternativeConverter extends ReflectionConverter { 
    public AlternativesConverter(Mapper mapper, ReflectionProvider reflectionProvider) { 
     super(mapper, reflectionProvider); 
    } 

    @Override 
    public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) { 
    if (reader.getAttribute("condition") != null) { 
    AlternativeA alternativeA = new AlternativeA(); 
    alternativeA.setUid(Integer.parseInt(reader.getAttribute("uid"))); 
    alternativeA.setCondition(reader.getAttribute("condition")); 
    return super.doUnmarshal(alternativeA, reader, context); 
    }else { 
    AlternativeB alternativeB = new AlternativeB(); 
    alternativeB.setUid(Integer.parseInt(reader.getAttribute("uid"))); 
    return super.doUnmarshal(alternativeB, reader, context); 
    } 
    } 

    @SuppressWarnings("unchecked") 
    @Override 
    public boolean canConvert(Class clazz) { 
     return Alternative.class.isAssignableFrom(clazz); 
    } 
} 

しかし、私はオブジェクトにxmlを変換しようとします。それが条件と代替に達すると、それは例外をスロー：あなたのいずれかがそのエラーを引き起こす可能性があるものにアイデアやint型を持っていますか

はAlternativeA

を入力するタイプのAlternativeBを変換することができませんか？ ありがとうございます。

Answer 1

のJava：

package de.mosst.spielwiese; 

import java.io.InputStream; 
import java.util.ArrayList; 
import java.util.List; 

import org.junit.Test; 

import com.thoughtworks.xstream.XStream; 
import com.thoughtworks.xstream.annotations.XStreamAlias; 
import com.thoughtworks.xstream.annotations.XStreamAsAttribute; 
import com.thoughtworks.xstream.converters.Converter; 
import com.thoughtworks.xstream.converters.UnmarshallingContext; 
import com.thoughtworks.xstream.converters.reflection.ReflectionConverter; 
import com.thoughtworks.xstream.converters.reflection.ReflectionProvider; 
import com.thoughtworks.xstream.io.HierarchicalStreamReader; 
import com.thoughtworks.xstream.mapper.Mapper; 

import lombok.Data; 

public class XStreamMultiClassesTest { 

    @Test 
    public void smokeTest() { 
     InputStream file = XStreamMultiClassesTest.class.getResourceAsStream("XStreamMultiClassesTest.xml"); 
     XStream xStream = new XStream(); 
     xStream.ignoreUnknownElements(); 
     xStream.processAnnotations(Mission.class); 
     xStream.processAnnotations(Alternative.class); 

     Converter converter = new AlternativeConverter(xStream.getMapper(), xStream.getReflectionProvider()); 
     xStream.registerConverter(converter); 

     Mission mission = (Mission) xStream.fromXML(file); 

     System.out.println(mission); 
     mission.branch.forEach(a -> { 
      System.out.println(a.getClass()); 
      if (a instanceof AlternativeA) { 
       System.out.println("- condition: " + ((AlternativeA) a).condition); 
      } 
     }); 
    } 

    public class AlternativeConverter extends ReflectionConverter { 

     public AlternativeConverter(Mapper mapper, ReflectionProvider reflectionProvider) { 
      super(mapper, reflectionProvider); 
     } 

     @Override 
     public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) { 
      Alternative alternative = null; 
      if (reader.getAttribute("condition") != null) { 
       alternative = new AlternativeA(); 
       ((AlternativeA) alternative).condition = reader.getAttribute("condition"); 
      } else { 
       alternative = new AlternativeB(); 
      } 
      alternative.uid = Integer.parseInt(reader.getAttribute("uid")); 
      return super.doUnmarshal(alternative, reader, context); 
     } 

     @Override 
     public boolean canConvert(@SuppressWarnings("rawtypes") Class clazz) { 
      return Alternative.class.isAssignableFrom(clazz); 
     } 
    } 

    @XStreamAlias("mission") 
    @Data 
    class Mission { 
     public List<Alternative> branch = new ArrayList<>(); 
    } 

    @XStreamAlias("alternative") 
    @Data 
    abstract class Alternative { 
     @XStreamAsAttribute 
     public int uid; 
     @XStreamAsAttribute 
     public String type; 
    } 

    class AlternativeA extends Alternative { 
     public String condition; 
    } 

    class AlternativeB extends Alternative { 
    } 

} 

XML：

<?xml version="1.0" encoding="UTF-8"?> 
<mission> 
    <branch> 
     <alternative uid="0" type="ALT_MONITOR" /> 
     <alternative uid="1" type="ALT_IF" condition="i==10" /> 
    </branch> 
</mission>