JAXB HashMap 不可映射 [英] JAXB HashMap unmappable

问题描述

我想将 POJO 类中的 HashMap 转换为 XML.我尝试使用 XmlAdapter 但它导致只有 HashMap 的键和值对是 XML 元素的属性.我需要 Key 是 Element 本身，HashMap 的值是元素的值.例如，我需要以下 XML:

I want to convert a HashMap in a POJO class to XML. I tried using the XmlAdapter but it results in only the key and value pairs of the HashMap being the attributes of the XML Elements. I need the Key to be the Element itself and the value of the HashMap to be the value of the element. For instance, I need the following XML:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<cart>
<supervisor_id>555</supervisor_id>
<payments>
    <payment sequence="1">
        <amount>123.45</amount>
        <billing_method>12345</billing_method>
        <form>card</form>
        <delivery_mode>Q</delivery_mode>
    </payment>
<payment sequence="2">
        <amount>123.45</amount>
        <person_id>2333</person_id>
        <form>cash</form>
        <delivery_mode>Q</delivery_mode>
    </payment>
</payments>
</cart>

我创建了以下类:MyMapType 包含 MyMapEntryType 类的列表，该类具有两个字段，即 Key 和 Value.如何将 Key 元素更改为 @XmlElement 并将 value 字段分配给 Key 字段?

I created the following classes: MyMapType holds a list of MyMapEntryType class which has two fields namely Key and Value. How do I change the Key element to be @XmlElement and assign the value field to the Key field?

这是我的源文件.

MyMapType.java

import java.util.ArrayList;
import java.util.List;

public class MyMapType {

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

    public List<MyMapEntryType> getEntry() {
        return entry;
    }

    public void setEntry(List<MyMapEntryType> entry) {
        this.entry = entry;
    }

}

MyMapEntryType.java

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlValue;

@XmlAccessorType(XmlAccessType.FIELD)
public class MyMapEntryType {

@XmlAttribute
private String key;
@XmlValue
private String value;
public String getKey() {
    return key;
}
public void setKey(String key) {
    this.key = key;
}
public String getValue() {
    return value;
}
public void setValue(String value) {
    this.value = value;
}
}

还请找到适配器类:

MyMapAdapter.java

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import javax.xml.bind.annotation.adapters.XmlAdapter;

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

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

        MyMapType myMapType = new MyMapType();

      for(Entry<String, String> entry : map.entrySet()) {
         MyMapEntryType myMapEntryType = new MyMapEntryType();
         myMapEntryType.setKey(entry.getKey());
         myMapEntryType.setValue(entry.getValue());
         myMapType.getEntry().add(myMapEntryType);
      }
      return myMapType;
   }

   @Override
   public Map<String, String> unmarshal(MyMapType map) throws Exception {
      HashMap<String, String> hashMap = new HashMap<String, String>();
      for(MyMapEntryType myEntryType : map.getEntry()) {
         hashMap.put(myEntryType.getKey(), myEntryType.getValue());
      }
      return hashMap;
   }
 }

这是具有 HashMap 字段的类:

This is the class which has the HashMap field:

XmlElementMap.java

@XmlAccessorType(XmlAccessType.FIELD)
public class XmlElementMap {

@XmlAttribute(name="sequence")
private int sequence;

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

public int getSequence() {
    return sequence;
}

public void setSequence(int sequence) {
    this.sequence = sequence;
}

public Map<String, String> getMap() {
    return map;
}

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


}

请告知如何实现这一点.

Please advise on how to achieve this.

问候，
-阿南德

Regards,
-Anand

目前它产生以下输出:

推荐答案

我有同样的要求我需要 Key 是 Element 本身，而 HashMap 的值是元素的值".

I have the same requirement "I need the Key to be the Element itself and the value of the HashMap to be the value of the element".

我没有使用自定义适配器，而是通过将 HashMap 条目动态转换为 JAXBElement 对象列表来实现它，然后使用@XmlAnyElement 注释该列表.

I didn't use customized adapter, but implemented it by converting the HashMap entries dynamically to a list of JAXBElement objects, and then annotated the list with @XmlAnyElement.

@XmlRootElement(name="root")
public class MyMapType {

    @XmlAnyElement
    public List<JAXBElement> entries = new ArrayList<JAXBElement>();

    public MyMapType() {    // JAXB required    
    }

    public MyMapType(Map<String, String> map) {
        for (Map.Entry<String, String> entry : map.entrySet()) {
            entries.add(new JAXBElement(new QName(entry.getKey()), 
                    String.class, entry.getValue()));
        }
    }

    public static void main(String[] args) throws Exception {
        JAXBContext context = JAXBContext.newInstance(MyMapType.class);
        Marshaller marshaller = context.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

        Map<String, String> map = new LinkedHashMap<String, String>();
        map.put("key1", "value1");
        map.put("key2", "value2");
        MyMapType mt = new MyMapType(map);

        marshaller.marshal(mt, System.out); 
    }
}

输出是，

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<root>
    <key1>value1</key1>
    <key2>value2</key2>
</root>

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