XML错误响应Spring REST和休眠状态

Question

I have Spring REST and hibernate in my project. I want to display the response in xml format but irrespective of the id I pass in the URL I am getting the incorrect xml response as below:

<COUNTRY id="0">
<population>0</population>
</COUNTRY>

The URL that I hit is :

http://localhost:8080/SpringRestHibernateExample/getCountry/2

Upon debug I have found that the id is correctly getting passed till the DAO layer and also the correct country is getting fetched. Somehow the rendering is not happening correctly. Here are my classes

Controller

@RequestMapping(value = "/getCountry/{id}", method = RequestMethod.GET, 
headers = "Accept=application/xml",
        produces="application/xml")
public Country getCountryById(@PathVariable int id) {

    return countryService.getCountry(id);
}

Model

@XmlRootElement (name = "COUNTRY")
@XmlAccessorType(XmlAccessType.FIELD)
@Entity
@Table(name="COUNTRY")
public class Country{

@XmlAttribute
@Id
@Column(name="id")
@GeneratedValue(strategy=GenerationType.IDENTITY)
int id;

@XmlElement
@Column(name="countryName")
String countryName; 

@XmlElement
@Column(name="population")
long population;

public Country() {
    super();
}

Service

@Transactional
 public Country getCountry(int id) {
    System.out.println("service"+id);
    return countryDao.getCountry(id);
}

DAO

public Country getCountry(int id) {
    System.out.println("dao"+id);
    Session session = this.sessionFactory.getCurrentSession();
    Country country = (Country) session.load(Country.class, new Integer(id));

    return country;
}

Can someone please help...

EDIT : replacing load with get solved the issue. But now for /getAllCountries I am receiving the below error:

The resource identified by this request is only capable of generating 
responses with characteristics not acceptable according to the request 
"accept" headers.

Below is the controller

 @RequestMapping(value = "/getAllCountries", method = 
 RequestMethod.GET,produces="application/xml",
        headers = "Accept=application/xml")
 public List<Country> getCountries() throws CustomerNotFoundException{

 List<Country> listOfCountries = countryService.getAllCountries();
 return listOfCountries;
}

Answer 1

The problem is your DAO method it uses Session.load instead of Session.get .

The difference between load and get is that load (generally always) returns a lazy proxy. It will only obtain the actual underlying data when data is actually requested (which could also lead to very late EntityNotFoundException s due to delayed checking in the database). Now generally you wouldn't notice any of the lazy stuff (maybe in performance) but in this case you do. you are outside of an active transaction (and thus Session ) and due to that the proxy cannot obtain the needed data from the database anymore (and because there isn't anything you will get 0 as that is the default for an int ).

Answer 2

I recommend to add to the @PathVariable the name of the parameter

Example @PathVariable("id")

Also if you are using an object as ID, you can like an integer use it in all the layer instead the int.

Also, the Integer could be null if is not desired, put in the PathVariable the attribute required = true. if null is not allowed

Finally if you are no planning to operate with the object and return it directly use session.get instead of session.load