从XML解析后，JAXB Unmarshaller在对象中返回null

Question

I have a String object with xml data in it . I want that data in POJO , i tried using JAXB unmarshaller to convert but it always give me null values in the object attributes.

this is my code :

ResponseEntity<String> response = restTemplate.getForEntity("https://api.flickr.com/services/rest/?api_key=MY_API_KEY&method=flickr.photos.search&tags=nature", String.class);    
String resp = response.getBody();

JAXBContext jaxBcontext = JAXBContext.newInstance(Resp.class);
Unmarshaller unmarshaller = jaxBcontext.createUnmarshaller();
Resp respObj = (Resp)unmarshaller.unmarshal(new StringReader(resp));

the value in String is :

 <rsp stat="ok">
 <photos page="1" pages="4226" perpage="100" total="422597">
 <photo id="28534349567" owner="79805131@N08" secret="b8bd7fe7cb" 
 server="843" farm="1" title="Savoie S006." ispublic="1" isfriend="0" 
 isfamily="0"/>
 <photo id="43355895332" owner="155237230@N05" secret="75fd48d040" 
 server="1769" farm="2" title="IMG_3139" ispublic="1" isfriend="0" 
 isfamily="0"/>
 <photo id="41595746070" owner="125407841@N08" secret="1f216ab8b8" 
 server="1822" farm="2" title="" ispublic="1" isfriend="0" isfamily="0"/>
 </photos>
 </rsp>

the POJOS are :

 @XmlAccessorType(XmlAccessType.FIELD)
 @XmlRootElement(name = "rsp")
 public class Resp {

    @XmlElement(name="stat")
    private String stat;

    @XmlElement(name="photos" , type = Photos.class)
    private Photos photos;

    public String getStat() {
        return stat;
    }
    //constructors and getter setters

---

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "photos")
public class Photos {

    @XmlElement(name="total")
    private String total;

    @XmlElement(name="page")
    private String page;

    @XmlElement(name="pages")
    private String pages;

    @XmlElement(name="perpage")
    private String perpage;

    @XmlElement(name="photo" , type=Photo.class)
    private List<Photo> photoObject = new ArrayList<Photo>();

    // constructors and getter setters.

---

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "photo")
public class Photo {

    @XmlElement(name="id")
    private String id;

    @XmlElement(name="isfamily")
    private String isfamily;

    @XmlElement(name="title")
    private String title;

    @XmlElement(name="ispublic")
    private String ispublic;

    @XmlElement(name="owner")
    private String owner;

    @XmlElement(name="secret")
    private String secret;

    @XmlElement(name="server")
    private String server;

    @XmlElement(name="isfriend")
    private String isfriend;

    // constructors and setter getter

the response i get is null values in all these objects.

Resp [stat=null, photos=Photos [total=null, page=null, pages=null, perpage=null, photo=]]

the value in String which i get is absolutely correct , but when i try to map my data to a POJO it starts giving error.

Other approach I used it to get the data directly in the object , like I have mentioned in my other question , but it also have some issues in that.

RestTemplate returns data in String but not populate list nested objects

if anyone can help in either one of these that'd be helpful.

Answer 1

As @f1sh already already commented, your problems are caused by several issues within your POJO classes

• In your XML response you have <rsp stat="ok">...</rsp> (ie stat is an XML attribute) instead of <rsp><stat>ok</stat>...</rsp> ( stat being an XML element).
  Therefore, in your Resp class the stat property needs to annotated with @XmlAttribute instead of @XmlElement .
• For the same reason, in your Photos class, all properties except for the photoObject property need to be annotated with @XmlAttribute instead of @XmlElement .
• For the same reason, in your Photo class all properties need to be annotated with @XmlAttribute instead of @XmlElement .

Some more best practices to consider:

• In your Photos and Photo classes you can remove the @XmlRootElement annotation because theses are not root elements. Only the Resp class is a root element and therefore needs @XmlRootElement .
• In your Photos class you should rename the photoObject property to photoObjects (with a plural s ) because it is a list. This would make the code easier to understand.

Answer 2

I found the solution .

The annotations @XMLAttribute and @XmlElements needed to be put on setters .

Did not work for getters and declarations.