CODEWITHSUNDEEP
jsonxmljaxbjersey
Amol
Amol

Reputation: 318

Is @XmlElement necessary for Jaxb

My question is, whether it is necessary to add @XmlElement before each element in your pojo to be picked up by jaxb, when making a JSON response. I am using jersey-json 1.17 . The reason I ask this is because, the example given on Jersey site does not use the annotation.

I get an out put as {}, but when I add @XmlElement before the attributes, I get the expected JSON output. Am I doing something wrong, because of which my JSON string is empty ?

My code :

The vertices list is populated in the constructor.

This produces the wrong output of {}

@XmlRootElement
public class SquareModel {
    List<Float> vertices = new ArrayList<Float>();
    ....
}

Whereas this produces the a correct JSON string :

@XmlRootElement
public class SquareModel {
    @XmlElement(name="vertices")
    List<Float> vertices = new ArrayList<Float>();
    ....
}

My resource class which returns the JSON 

@GET
@Produces(MediaType.APPLICATION_JSON)
public SquareModel getJsonString() {
    return new SquareModel();
}

Thanks :)

Upvotes: 3

Views: 2614

Answers (2)

bdoughan
bdoughan

Reputation: 149047

No, by default a JAXB (JSR-22@) implementation will treat all public fields and properties (get/set combinations) as mapped (not requiring the @XmlElement annotation).

If you wish to annotate a field I would recommend annotating your class with @XmlAccessorType(XmlAccessType.FIELD)

Upvotes: 1

Shmil The Cat
Shmil The Cat

Reputation: 4668

According to this http://jersey.java.net/nonav/documentation/latest/json.html#json.jaxb.approach.section You should have this annotation (I'm also using it in my code, even though it XML oriented, but it gives me cool JSON also)

Taking this approach will save you a lot of time, if you want to easily produce/consume both JSON and XML data format. Because even then you will still be able to use a unified Java model. Another advantage is simplicity of working with such a model, as JAXB leverages annotated POJOs and these could be handled as simple Java beans.

A disadvantage of JAXB based approach could be if you need to work with a very specific JSON format. Then it could be difficult to find a proper way to get such a format produced and consumed. This is a reason why a lot of configuration options are provided, so that you can control how things get serialized out and deserialized back.

Following is a very simple example of how a JAXB bean could look like.

Example 5.3. Simple JAXB bean implementation

@XmlRootElement
   public class MyJaxbBean {
     public String name;
     public int age;

     public MyJaxbBean() {} // JAXB needs this

     public MyJaxbBean(String name, int age) {
       this.name = name;
      this.age = age;
    }
  }

Upvotes: 0

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