JAXB @XmlJavaTypeAdapter用法

Question

我一直在努力@XMLJavaTypeAdapter让它按照我的需要工作.我的理解可能是错的.请帮助我更好地理解.

要求:例如:我有一个带有映射对象列表的传输XML,如下所示:

<transport>
    <mappings>
        <product>XXX</product>
        <eventName>XXX</eventName>
        <destination>XXX</destination>
        <destinationType>XXX</destinationType>
    </mappings>
</transport>

使用JAXB,我能够将XML作为List<Mappings>对象读取.

我想将我的内存表示List<Mappings>为a Map<String,Mappings>,其中map中的键是product:eventName和在我的代码中使用Map而不是List<Mapping>.

我对使用有点困惑,@XmlJavaTypeAdapter无法弄清楚如何实现这一目标.

在这方面的任何帮助将受到高度赞赏.

谢谢Raj

Answer 1

注意: 我是EclipseLink JAXB(MOXy)的负责人,也是JAXB 2(JSR-222)专家组的成员.

您可以利用@XmlPathMOXy中的扩展来执行以下操作:

运输

该Transport班利用了的@XmlPath扩展.如果没有@XmlPath调用的分组元素mappings将添加到文档中.

package forum8403623;

import java.util.*;
import javax.xml.bind.annotation.*;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
import org.eclipse.persistence.oxm.annotations.XmlPath;

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

    @XmlJavaTypeAdapter(MappingsAdapter.class)
    @XmlPath(".")
    private Map<String, Mapping> mappings = new HashMap<String, Mapping>();

}

制图

package forum8403623;

import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(propOrder={"product", "eventName", "destination", "destinationType"})
public class Mapping {

    String product;
    String eventName;
    String destination;
    String destinationType;

}

MappingsAdapter

以下类负责转换为/将从Map<String, Mapping>我们将用于XML映射的表示转换.

package forum8403623;

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

public class MappingsAdapter extends XmlAdapter<MappingsAdapter.AdaptedMap, Map<String, Mapping>>{

    @Override
    public Map<String, Mapping> unmarshal(AdaptedMap v) throws Exception {
        Map<String, Mapping> mappings = new HashMap<String, Mapping>();
        for(Mapping mapping : v.mappings) {
            mappings.put(mapping.product, mapping);
        }
        return mappings;
    }

    @Override
    public AdaptedMap marshal(Map<String, Mapping> v) throws Exception {
        AdaptedMap adaptedMap = new AdaptedMap();
        for(Entry<String,Mapping> entry : v.entrySet()) {
            adaptedMap.mappings.add(entry.getValue());
        }
        return adaptedMap;
    }

    static class AdaptedMap {
        public List<Mapping> mappings = new ArrayList<Mapping>();
    }
}

演示

package forum8403623;

import java.io.File;
import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Transport.class);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum8403623/input.xml");
        Transport transport = (Transport) unmarshaller.unmarshal(xml);

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

}

jaxb.properties

要将MOXy用作JAXB提供程序,您需要在与域模型相同的包中添加名为jaxb.properties的文件,并使用以下条目:

javax.xml.bind.context.factory = org.eclipse.persistence.jaxb.JAXBContextFactory

欲获得更多信息

• http://blog.bdoughan.com/2010/07/xmladapter-jaxbs-secret-weapon.html
• http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html
• http://blog.bdoughan.com/2010/07/xpath-based-mapping.html