自定义映射<Object，Object> XmlAdapter

我试图将Map<Integer,String>XmlAdapter修改为支持Map<Object,Object>的映射。该方法是基于这篇文章：XmlAdapter - JAXB's Secret Weapon 自定义映射<Object，Object> XmlAdapter

这条线的测试工具生成NullPointerException：

JAXBContext jc = JAXBContext.newInstance(Foo.class);

如果我改变线束和MapAdapter/MapEntry为T<Integer,String>，代码工作正常。

我错过了什么？可以将Object类型序列化，还是需要将其转换为另一个不太抽象的类？如果是这样，我会认为我会在marshal()方法中遇到这个错误，但它似乎永远不会达到这一点（至少在Netbean的调试器中）。

MapEntryType：

public class MyMapEntryType { 

    @XmlAttribute 
    public Object key; 

    @XmlValue 
    public Object value; 

}

的MapType：

public class MyMapType { 

    public List<MyMapEntryType> entry = new ArrayList<MyMapEntryType>(); 

}

MapAdapter：

public final class MyMapAdapter extends 

    XmlAdapter<MyMapType,Map<Object, Object>> { 

    @Override 
    public MyMapType marshal(Map<Object, Object> arg0) throws Exception { 

     MyMapType myMapType = new MyMapType(); 

     for(Entry<Object, Object> entry : arg0.entrySet()) { 

     MyMapEntryType myMapEntryType = new MyMapEntryType(); 
     myMapEntryType.key = entry.getKey(); 
     myMapEntryType.value = entry.getValue(); 
     myMapType.entry.add(myMapEntryType); 

     } 

     return myMapType; 
    } 

    @Override 
    public Map<Object, Object> unmarshal(MyMapType arg0) throws Exception { 

     HashMap<Object, Object> hashMap = new HashMap<Object, Object>(); 

     for(MyMapEntryType myEntryType : arg0.entry) { 
     hashMap.put(myEntryType.key, myEntryType.value); 
     } 

     return hashMap; 
    } 

}

对象将被编组/解组：

@XmlRootElement 
@XmlAccessorType(XmlAccessType.FIELD) 
public class Foo { 

    @XmlJavaTypeAdapter(MyMapAdapter.class) 
    Map<Object, Object> map = new HashMap<Object, Object>(); 

    public Map getMap() { 
     return map; 
    } 

    public void setMap(Map map) { 
     this.map = map; 
    } 

}

测试工具：

Map<Object,Object> xyz = new HashMap<Object,Object>(); 
xyz.put("key0", "value0"); 
xyz.put("key1", "value1"); 

Foo foo = new Foo(); 
foo.setMap(xyz); 

//generates NullPointerException     
JAXBContext jc = JAXBContext.newInstance(Foo.class); 

Marshaller marshaller = jc.createMarshaller(); 
marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); 
marshaller.marshal(foo, System.out);

堆栈跟踪：

java.lang.NullPointerException 
    at com.sun.xml.internal.bind.v2.runtime.reflect.TransducedAccessor.get(TransducedAccessor.java:154) 
    at com.sun.xml.internal.bind.v2.runtime.property.ValueProperty.<init>(ValueProperty.java:66) 
    at com.sun.xml.internal.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:95) 
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.<init>(ClassBeanInfoImpl.java:145) 
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:479) 
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:498) 
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.<init>(ArrayElementProperty.java:97) 
    at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementNodeProperty.<init>(ArrayElementNodeProperty.java:47) 
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) 
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) 
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513) 
    at com.sun.xml.internal.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:113) 
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.<init>(ClassBeanInfoImpl.java:145) 
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:479) 
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:498) 
    at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.<init>(SingleElementNodeProperty.java:90) 
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) 
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) 
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) 
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513) 
    at com.sun.xml.internal.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:113) 
    at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.<init>(ClassBeanInfoImpl.java:145) 
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:479) 
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.<init>(JAXBContextImpl.java:305) 
    at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1100) 
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:143) 
    at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:110) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
    at java.lang.reflect.Method.invoke(Method.java:597) 
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:228) 
    at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:215) 
    at javax.xml.bind.ContextFinder.find(ContextFinder.java:414) 
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:618) 
    at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:565)

我改变了地图从Map<Object,Object>到Map<String,Object>以更好地代表我需要（我也改变了所有的内部对象的匹配这一点）。我在MyMapEntryType类的Object属性中添加了@XmlAnyElement和@XmlMixed注释;我删除了@XmlValue注释。

当我调试的代码，这行不产生错误（华友世纪）：

JAXBContext jc = JAXBContext.newInstance(PropertyBag.class);

但是，试图名帅此项：

xyz.put("key0", 1);

结果在读取错误：

unable to marshal type `java.lang.Integer` as an element because it is missing an `@XmlRootElement` annotation

来源

2012-01-27 craig

我可能是错的，但我认为JAXB不能做类型探索。在你原来的情况下，你在'MyMapEntryType'中有对象。数组是对象，映射是对象，原始包装器是对象，其他任何复合类实例都是对象。 JAXB如何通过查看此对象来确定要使用的序列化程序？它可以是“普通”类型的内置序列化器，但未知类型需要另外一个链中的适配器。 – 2012-01-28 11:45:30

所以，我需要一个XmlAdapter为每个非常见的类型？ – craig 2012-01-28 23:23:59

是的。基本类型如String，Date，List，所有原语已经被支持，但其余的你需要以这种或那种方式明确地声明如何（去）序列化它们。这里的重点是JAXB在创建上下文时构建所有类的元模型（以及可能的XML映射），而不是在编组完成时。对于'Object'类型，JAXB无法发现可能的方法来进行编组。如果你想隐藏在Object后面的那段XML是不同的，那么你需要去['@ XmlAnyElement']（http://stackoverflow.com/questions/9040695）的方式。 – 2012-01-29 08:53:03

我只是看看周围，并遇到this reply。因此，您可以使用的是@XmlAnyElement和自定义XML < - > DOM转换器，或者您需要明确指定@XmlElementRefs该属性的可能类别。

来源

2012-01-28 13:21:45

我能够通过使用地图内部来解决这个问题：

MyMapEntryType：

public class MyMapEntryType { 

    @XmlAttribute 
    public String key; 

    @XmlValue 
    public String value; 

    private MyMapEntryType() { 
     //Required by JAXB 
    } 

    public MyMapEntryType(String key, String value) { 
     this.key = key; 
     this.value = value; 
    } 

}

MyMapType类：

public class MyMapType { 

    @XmlElement(name="Property") 
    public List<MyMapEntryType> entry = new ArrayList<MyMapEntryType>(); 

} 

public class MyMapAdapter extends XmlAdapter<MyMapType, Map<String,Object>> { 

    @Override 
    public MyMapType marshal(Map<String,Object> bt) throws Exception { 

     MyMapType myMapType = new MyMapType(); 

     for(Map.Entry<String,Object> entry : bt.entrySet()) { 

      MyMapEntryType myMapEntryType = new MyMapEntryType(entry.getKey(), entry.getValue().toString()); 
      myMapType.entry.add(myMapEntryType); 

     } 

     return myMapType; 

    } 

    ... 

}

属性包（NEE美孚）类：

@XmlRootElement(name="PropertyBag") 
public class PropertyBag { 

    private Map<String,Object> map; 

    public PropertyBag() { 
     map = new HashMap<String,Object>(); 
    } 

    @XmlJavaTypeAdapter(MyMapAdapter.class) 
    @XmlElement(name="Properties") 
    public Map<String,Object> getMap() { 
     return map; 
    } 

    public void setMap(Map<String,Object> map) { 
     this.map = map; 
    } 

}

Harnes S：

 Map<String, Object> parent = new HashMap<String, Object>(); 
     parent.put("SI_EMAIL_ADDRESS", "[email protected]"); 
     parent.put("SI_DATE", new Date()); 
     parent.put("SI_GUID", "ATQJj1RvgVlLqDqP_VOGltM"); 
     parent.put("SI_BOOLEAN", true); 
     parent.put("SI_INT", 1318); 
     parent.put("SI_LONG", new Long(123456789)); 
     parent.put("SI_INTEGER", new Integer(23456)); 


     PropertyBag bag = new PropertyBag(); 
     bag.setMap(parent); 

     JAXBContext jc = JAXBContext.newInstance(PropertyBag.class);    
     Marshaller marshaller = jc.createMarshaller(); 
     marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true); 
     marshaller.marshal(bag, System.out);

输出：

<PropertyBag> 
    <Properties> 
     <Property key="SI_INT">1318</Property> 
     <Property key="SI_DATE">Wed Feb 01 22:18:35 EST 2012</Property> 
     <Property key="SI_BOOLEAN">true</Property> 
     <Property key="SI_LONG">123456789</Property> 
     <Property key="SI_INTEGER">23456</Property> 
     <Property key="SI_GUID">ATQJj1RvgVlLqDqP_VOGltM</Property> 
     <Property key="SI_EMAIL_ADDRESS">[email protected]</Property> 
    </Properties> 
</PropertyBag>

理想情况下，我想有XML表示如下：

<Properties> 
    <SI_INT>1318</SI_INT> 
    <SI_DATE>Wed Feb 01 22:18:35 EST 2012</SI_DATE> 
    <SI_BOOLEAN>true</SI_BOOLEAN> 
    <SI_LONG>123456789</SI_LONG> 
    <SI_INTEGER>23456</SI_INTEGER> 
    <SI_GUID>ATQJj1RvgVlLqDqP_VOGltM</SI_GUID> 
    <SI_EMAIL_ADDRESS>[email protected]</SI_EMAIL_ADDRESS> 
</Properties>

我还希望能够连载子属性：

... 

Map<String,Object> child = new HashMap<String,Object>(); 
child.put("1", 33217); 
child.put("2", 36351); 
child.put("SI_TOTAL", 2); 
parent.put("SI_LIST", child);

这将代表编辑：

<Properties> 
    <SI_INT>1318</SI_INT> 
    <SI_DATE>Wed Feb 01 22:18:35 EST 2012</SI_DATE> 
    <SI_BOOLEAN>true</SI_BOOLEAN> 
    <SI_LONG>123456789</SI_LONG> 
    <SI_INTEGER>23456</SI_INTEGER> 
    <SI_GUID>ATQJj1RvgVlLqDqP_VOGltM</SI_GUID> 
    <SI_EMAIL_ADDRESS>[email protected]</SI_EMAIL_ADDRESS> 
    <SI_LIST> 
     <!-- numeric elements are illegal; refactor --> 
     <1>33217</1> 
     <2>36351</2> 
     <SI_TOTAL>2</SI_TOTAL> 
    </SI_LIST> 
</Properties>

但我不确定，我可以使用注释转换密钥名称为元素。

来源

2012-02-02 03:46:24 craig

自定义映射<Object，Object> XmlAdapter

回答

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