JSON String to Object Mapping

Question

I am having an JSON Response and what I need is to Map the corresponding JSON String to the particular Response class.Is there any tools or framework to do the same.

Response class is:

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

@XmlRootElement(name = "0")
@XmlAccessorType(XmlAccessType.FIELD)
public class Student {

     @XmlElement(name="0")
     private String firstName;
     @XmlElement(name="1")
     private String lastName;

     public String getFirstName() {
         return firstName;
     }
     public void setFirstName(String firstName) {
         this.firstName = firstName;
     }
     public String getLastName() {
         return lastName;
     }
     public void setLastName(String lastName) {
         this.lastName = lastName;
     }
}

Json Response String is {"0":{"0":"Rockey","1":"John"}}

I am using Apache CXF Framework with Jettison as the JSON Provider also uses JAXB to wire the data to low bandwidth clients.

Please make a note that I want to convert the number representations to corresponding fields.

Answer 1

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group.

Below is how you an support your use case with your Student class as annotated with EclipseLink JAXB (MOXy).

Demo

import java.io.StringReader;
import java.util.*;
import javax.xml.bind.*;

public class Demo {

    public static void main(String[] args) throws Exception {
        Map<String, Object> properties = new HashMap<String, Object>(1);
        properties.put("eclipselink.media-type", "application/json");
        JAXBContext jc = JAXBContext.newInstance(new Class[] {Student.class}, properties);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        StringReader json = new StringReader("{\"0\":{\"0\":\"Rockey\",\"1\":\"John\"}}");
        Student student = (Student) unmarshaller.unmarshal(json);

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

}

Output

{
   "0" : {
      "0" : "Rockey",
      "1" : "John"
   }
}

jaxb.properties

To use MOXy as your JAXB provider you need to include a file called jaxb.properties in the same package as your domain model with the following entry:

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

---

MOXy and JAX-RS

For JAX-RS applications you can leverage the MOXyJsonProvider class to enable JSON-binding (see: http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html).

• http://blog.bdoughan.com/2012/05/moxy-as-your-jax-rs-json-provider.html

Answer 2

You can refer Google-GSON library - https://github.com/google/gson

You can also refer earlier stackoverflow answer - Convert a JSON string to object in Java ME?

Answer 3

Jettison could do this. Found a sample code of unmarshalling JSON to object with JAXB here:

JAXBContext jc = JAXBContext.newInstance(Customer.class);

JSONObject obj = new JSONObject("{\"customer\":{\"id\":123,\"first-name\":\"Jane\",\"last-name\":\"Doe\",\"address\":{\"street\":\"123 A Street\"},\"phone-number\":[{\"@type\":\"work\",\"$\":\"555-1111\"},{\"@type\":\"cell\",\"$\":\"555-2222\"}]}}");
Configuration config = new Configuration();
MappedNamespaceConvention con = new MappedNamespaceConvention(config);
XMLStreamReader xmlStreamReader = new MappedXMLStreamReader(obj, con);

Unmarshaller unmarshaller = jc.createUnmarshaller();
Customer customer = (Customer) unmarshaller.unmarshal(xmlStreamReader);