ヌル値を返す非マーシャル

-1

cars.xmlを非整列化しようとしていますが、ヌル値を返しています。 xmlで1台の車でこのメソッドを試してみましたが、Listに問題があります。ヌル値を返す非マーシャル

メインクラス：

import java.io.BufferedReader; 
import java.io.InputStreamReader; 
import java.net.HttpURLConnection; 
import java.net.URL; 
import javax.xml.bind.JAXBContext; 
import javax.xml.bind.Unmarshaller; 

public class Teste { 

    private final String USER_AGENT = "Mozilla/5.0"; 

    public static void main(String[] args) throws Exception { 

    Teste http = new Teste(); 

    System.out.println("Testing 1 - Send Http GET request"); 
    http.sendGet(); 

//  System.out.println("\nTesting 2 - Send Http POST request"); 
//  http.sendPost(); 
    } 

    // HTTP GET request 
    private void sendGet() throws Exception { 

    String url = "http://www.teste.com/cars.xml"; 

    URL obj = new URL(url); 
    HttpURLConnection con = (HttpURLConnection) obj.openConnection(); 

    // optional default is GET 
    con.setRequestMethod("GET"); 

    //add request header 
    con.setRequestProperty("User-Agent", USER_AGENT); 

    int responseCode = con.getResponseCode(); 
    System.out.println("\nSending 'GET' request to URL : " + url); 
    System.out.println("Response Code : " + responseCode); 

    BufferedReader in = new BufferedReader(
      new InputStreamReader(con.getInputStream())); 

    try { 

     //Transforma xml em objeto 
     JAXBContext aXBContext = JAXBContext.newInstance(Cars.class); 
     Unmarshaller cu = aXBContext.createUnmarshaller(); 
     Cars cars = (Cars) cu.unmarshal(in); 



     if(cars != null){ 
     System.out.println("Não é nulo!"); 
     } 

    } catch (Exception e) { 
     System.out.println(e.getMessage()); 
    } 

    } 
}

車クラス：

import java.util.ArrayList; 
import javax.xml.bind.annotation.XmlElement; 
import javax.xml.bind.annotation.XmlRootElement; 


@XmlRootElement (name = "Cars") 

public class Cars { 
    private ArrayList<Car> cars = new ArrayList<>(); 

    public ArrayList<Car> getCars() { 
    return cars; 
    } 

    @XmlElement 
    public void setCars(ArrayList<Car> cars) { 
    this.cars = cars; 
    } 

}

Carクラス：

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

@XmlRootElement(name = "Car") 
public class Car { 

    private String manufacturerCar; 
    private String modelCar; 
    private String doorsCar; 
    private String gearshift; 

    public String getManufacturerCar() { 
    return manufacturerCar; 
    } 

    @XmlElement 
    public void setManufacturerCar(String manufacturerCar) { 
    this.manufacturerCar = manufacturerCar; 
    } 

    public String getModelCar() { 
    return modelCar; 
    } 

    @XmlElement 
    public void setModelCar(String modelCar) { 
    this.modelCar = modelCar; 
    } 

    public String getDoorsCar() { 
    return doorsCar; 
    } 

    @XmlElement 
    public void setDoorsCar(String doorsCar) { 
    this.doorsCar = doorsCar; 
    } 

    public String getGearshift() { 
    return gearshift; 
    } 

    @XmlElement 
    public void setGearshift(String gearshift) { 
    this.gearshift = gearshift; 
    } 

    @Override 
    public String toString() { 
    return "Car{" + "manufacturerCar=" + manufacturerCar + ", modelCar=" + modelCar + ", doorsCar=" + doorsCar + ", gearshift=" + gearshift + '}'; 
    } 
}

とXML：

<Cars> 
<Car> 
<manufacturerCar>VW</manufacturerCar> 
<modelCar>FUSCA</modelCar> 
<doorsCar>2</doorsCar> 
<gearshift>MANUAL</gearshift> 
</Car> 
<Car> 
<manufacturerCar>FORD</manufacturerCar> 
<modelCar>FOCUS</modelCar> 
<doorsCar>4</doorsCar> 
<gearshift>AUTOMATICO</gearshift> 
</Car> 
<Car> 
<manufacturerCar>FIAT</manufacturerCar> 
<modelCar>UNO</modelCar> 
<doorsCar>4</doorsCar> 
<gearshift>MANUAL</gearshift> 
</Car> 
<Car> 
<manufacturerCar>VW</manufacturerCar> 
<modelCar>UP!</modelCar> 
<doorsCar>4</doorsCar> 
<gearshift>AUTOMATICO</gearshift> 
</Car> 
<Car> 
<manufacturerCar>PORSHE</manufacturerCar> 
<modelCar>Q100</modelCar> 
<doorsCar>2</doorsCar> 
<gearshift>AUTOMATICO</gearshift> 
</Car> 
<Car> 
<manufacturerCar>RENAULT</manufacturerCar> 
<modelCar>DUSTER</modelCar> 
<doorsCar>4</doorsCar> 
<gearshift>Manual</gearshift> 
</Car> 
<Car> 
<manufacturerCar>HONDA</manufacturerCar> 
<modelCar>CIVIC</modelCar> 
<doorsCar>4</doorsCar> 
<gearshift>Manual</gearshift> 
</Car> 
<Car> 
<manufacturerCar>MITSUBISHI</manufacturerCar> 
<modelCar>PAJERO</modelCar> 
<doorsCar>4</doorsCar> 
<gearshift>Manual</gearshift> 
</Car> 
</Cars>

私はプロジェクトをデキューするとき、nullを返します。問題はJAXBタグだと思っていましたが、どのようにしてその問題を解決するのか誠実には分かりません。

出典

2017-09-29 G. Falcão