问如何为JAXB MOXy编写JsonStructure (JSR-353) XmlAdaptor？
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Stack Overflow用户

提问于 2015-02-24 17:58:05

回答 1查看 1.4K关注 0票数 2

我需要将一些任意的JSON内容包装到POJO中，然后使用MOXy/JAXB序列化到JSON，但是我不知道如何将JsonObject与JAXB绑定。我只需要编组JsonObject，不需要解组。

即拥有POJO：

@XmlRootElement
public class MsgPOJO {
  public String type;
  public Object content;
}

如何将任意JSON内容放入MsgPOJO.content中，并将其序列化：

String jsonDoc = "{\"prop\":\"value\"}";
MsgPOJO msg = new MsgPOJO();
msg.type = "whatever";
msg.content = jsonDoc;

因此这将是输出：

{
  "type": "whatever",
  "content": {
    "prop": "value"
   }
}

我正在考虑用@XmlJavaTypeAdapter对MsgPOJO.content进行注释，但这似乎无济于事，因为JSON内容可能是任意的。

如果moxy可以编组JsonObject或JsonStructure就好了，这样我就可以像这样定义POJO：

@XmlRootElement
public class MsgPOJO {
  public String type;
  public JsonObject content;
}

有没有办法做到这一点呢？或者它是MOXy/JAXB中的一个限制？

java

json

jaxb

moxy

jsr-353

回答 1

Stack Overflow用户

发布于 2015-02-24 23:02:52

默认情况下，MOXy不支持JSON-P结构的编组/解组，您需要实现XmlJavaTypeAdapter。下面是JsonObject适配器的示例。

MsgPOJO.java

package org.eclipse.persistence.testing.jsonp;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlRootElement;

/**
 * Created by mvojtek on 24/02/15.
 */
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class MsgPOJO {

    public String type;

    public JsonObjectWrapper content;

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public JsonObjectWrapper getContent() {
        return content;
    }

    public void setContent(JsonObjectWrapper content) {
        this.content = content;
    }

    @Override
    public String toString() {
        return "MsgPOJO{" +
                "type='" + type + '\'' +
                ", content=" + content +
                '}';
    }
}

JsonObjectWrapper.java

package org.eclipse.persistence.testing.jsonp;

import javax.json.JsonObject;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

/**
 * Created by mvojtek on 24/02/15.
 */
@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class JsonObjectWrapper {

    @XmlJavaTypeAdapter(JsonObjectAdapter.class)
    private JsonObject jsonObject;

    public JsonObject getJsonObject() {
        return jsonObject;
    }

    public void setJsonObject(JsonObject jsonObject) {
        this.jsonObject = jsonObject;
    }

    @Override
    public String toString() {
        return "JsonObjectWrapper{" +
                "jsonObject=" + jsonObject +
                '}';
    }
}

JsonObjectAdapter.java

package org.eclipse.persistence.testing.jsonp;

import javax.json.Json;
import javax.json.JsonObject;
import javax.json.JsonReader;
import javax.xml.bind.annotation.adapters.XmlAdapter;
import java.io.StringReader;

/**
 * Created by mvojtek on 24/02/15.
 */
public final class JsonObjectAdapter extends XmlAdapter<String,JsonObject> {
    @Override
    public String marshal(JsonObject v) throws Exception {
        if (null == v) {
            return null;
        }
        return v.toString();
    }

    @Override
    public JsonObject unmarshal(String v) throws Exception {
        if (null == v) {
            return null;
        }
        JsonReader jsonReader = Json.createReader(new StringReader(v));
        return jsonReader.readObject();
    }
}

Test.java

package org.eclipse.persistence.testing.jsonp;

import org.eclipse.persistence.jaxb.JAXBContextFactory;
import org.eclipse.persistence.jaxb.JAXBContextProperties;
import org.eclipse.persistence.oxm.MediaType;

import javax.json.Json;
import javax.json.JsonReader;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import java.io.StringReader;
import java.io.StringWriter;

public class Test {

    public static void main(String[] args) throws Exception {

        //marshal
        JAXBContext jaxbContext = JAXBContextFactory.createContext(new Class[]{MsgPOJO.class}, null);

        Marshaller marshaller = jaxbContext.createMarshaller();
        marshaller.setProperty(JAXBContextProperties.MEDIA_TYPE, MediaType.APPLICATION_JSON);

        MsgPOJO msgPOJO = new MsgPOJO();
        msgPOJO.setType("myType");

        JsonReader jsonReader = Json.createReader(new StringReader("{\"prop\":\"value\"}"));

        JsonObjectWrapper wrapper = new JsonObjectWrapper();
        wrapper.setJsonObject(jsonReader.readObject());

        msgPOJO.setContent(wrapper);

        StringWriter marshallerOutput = new StringWriter();

        marshaller.marshal(msgPOJO, marshallerOutput);

        String result = marshallerOutput.toString();
        System.out.println("marshal result = "+result);

        //unmarshal
        Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
        unmarshaller.setProperty(JAXBContextProperties.MEDIA_TYPE, MediaType.APPLICATION_JSON);
        unmarshaller.setProperty(JAXBContextProperties.JSON_INCLUDE_ROOT, true);

        MsgPOJO msgPOJO2 = (MsgPOJO)unmarshaller.unmarshal(new StringReader(result));

        System.out.println("msgPOJO2="+msgPOJO2);
    }
}