Unmarshal the List Object Created in POJO classes

Question

I created one Object class which will be my root element and in that I have two attributes and one element shown below:

import java.util.List;

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

@XmlRootElement 
public class Object {
    
    private String id;
    private String type;
    List <UniqueId> UniqueId;
    
    public List<UniqueId> getUniqueId() {
        return UniqueId;
    }
    public void setUniqueId(List<UniqueId> uniqueId) {
        UniqueId = uniqueId;
    }
    @XmlAttribute
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    @XmlAttribute
    public String getType() {
        return type;
    }
    public void setType(String type) {
        this.type = type;
    }
    
    public Object() {
        super();
    }
    public Object(String id, String type, List<classes.UniqueId> uniqueId) {
        super();
        this.id = id;
        this.type = type;
        UniqueId = uniqueId;
    }
        
}

and then one class for List <UniqueId> UniqueId;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class UniqueId {
    
    private String Uid;

    public String getUid() {
        return Uid;
    }

    public void setUid(String uid) {
        Uid = uid;
    }

    public UniqueId(String uid) {
        super();
        Uid = uid;
    }

    public UniqueId() {
        super();
    }

}

and in the main class, I want to Unmarshal the UniqueId data from VPMobject and I'm getting null value there. How can I fetch the uniqueId if there are n UId's present in the xml file?

import java.io.File;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;


import pojoClasses.VPMObject;


public class MarshalEAD {

    public static void main(String[] args) { 
        try {
           File f1 = new File("src\\xmlData\\Test1.xml");
           JAXBContext contextObj = JAXBContext.newInstance(Assembly.class);
            Unmarshaller unmarshal = contextObj.createUnmarshaller();
        
            // add information or objects to be fetched and written as output
            
          Assembly AD= (Assembly)unmarshal.unmarshal(f1);
            
          System.out.println("Extracted Xml File Information:\n\t");
          System.out.println("Root Element: ");
          
          List<VPMObject> list = AD.getVPMObject();  
            for(VPMObject fetch:list)  {
                System.out.println("ID: " + fetch.getId());
                System.out.println("Type: " + fetch.getType());
                System.out.println("UniqueId: " + fetch.getUniqueId() );
                
            }
            
       } 
       catch (Exception e) {
        // TODO: handle exception
        System.out.println(e.getMessage());
       }
      
    }  
      
}