如何爲JAXB MOXy編寫JsonStructure（JSR-353）XmlAdaptor？

Question

我需要將一些任意的JSON內容包裝到POJO中，然後使用MOXy/JAXB將其序列化爲JSON，但無法弄清楚如何將JsonObject與JAXB綁定。我只需要編組JsonObject，解組並不是必需的。

即具有POJO：

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

如何把一個任意JSON內容在 'MsgPOJO.content'，並對其進行序列化：

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

所以，這將是輸出：

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

我在考慮用@XmlJavaTypeAdapter註釋MsgPOJO.content，但這似乎並不能讓我獲得任何地方，因爲JSON內容可能是任意的。

這將是很好，如果能MOXY元帥JsonObject或JsonStructure，所以我可以這樣定義的POJO：

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

有沒有一種方法，使這項工作？或者它是MOXy/JAXB的限制嗎？

Answer 1

默認情況下，MOXy不支持JSON-P結構的編組/解組，您需要實現XmlJavaTypeAdapter。以下是JsonObject適配器的示例。

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); 
    } 
} 

如果你不想要字符串，你可以在MyList和MyMap結構的幫助下編寫一般結構。之後，您可以編寫XmlJavaTypeAdapter，將JsonObject編組爲此新類型。結果將是json，不是與輸入的字符串表示相同，而是合法的json。

https://github.com/eclipse/eclipselink.runtime/blob/master/moxy/eclipselink.moxy.test/src/org/eclipse/persistence/testing/jaxb/rs/model/MyList.java

https://github.com/eclipse/eclipselink.runtime/blob/master/moxy/eclipselink.moxy.test/src/org/eclipse/persistence/testing/jaxb/rs/model/MyMap.java