ClassCastException 类型转换异常 class.Accommodation 无法转换为 class.Attraction。

huangapple
go评论111阅读模式
英文:

ClassCastException class.Accomodation cannot be cast to class.Attraction

问题

这是我的模型：

  1. public class Accomodation {
  2.     ...
  3. }

以及

  1. public class Attraction extends Accomodation {
  2.     ...
  3.     private String openingTime;
  4. }

我在我的 Controller 类中有这个方法：

  1. protected Accomodation getAccomodationByFormData(CrudView crudView) {
  2.     Accomodation accomodation = new Accomodation();
  3.     // 设置器方法
  4.     return accomodation;
  5. }

该方法在 AttractionController 中使用（该类扩展了之前的 Controller）：

  1. @Override
  2. protected Accomodation getAccomodationByFormData(CrudView crudView) {
  3.     Attraction attraction = (Attraction) super.getAccomodationByFormData(crudAttractionView);
  4.     attraction.setOpeningTime(getOpeningTimeWithFormData()); 
  5.     return attraction;
  6. }

在这个 AttractionController 的另一个地方，我有：

  1. ...
  2. Attraction attraction = (Attraction) getAccomodationByFormData(crudAttractionView); // 抛出 ClassCastException
  3. ...

但是这给了我以下错误：

  1. > 异常线程 "JavaFX Application Thread" java.lang.ClassCastException: class models.Accomodation cannot be cast to class models.Attraction (models.Accomodation and models.Attraction are in unnamed module of loader 'app')
  2.     at controllers.CrudAttractionController.getAccomodationByFormData(CrudAttractionController.java:302)
  3.     at controllers.CrudAttractionController.lambda$buttonConfermaClicked$4(CrudAttractionController.java:143)
  4.     ...

（注：请注意 CrudAttractionView 类扩展了 CrudView）

  • 如何修复？

编辑

Attraction

  1. public class Attraction extends Accomodation {
  2.     private String openingTime;
  4.     public Attraction() {
  6.     }
  8.     public Attraction(Accomodation accomodation) {
  9.         super(accomodation);
  10.     }
  12.     // 获取器和设置器方法
  13. }

Accomodation

  1. public class Accomodation implements Serializable {
  2.     protected String id;
  3.     protected String name;
  4.     protected Integer avarageRating;
  5.     protected Integer avaragePrice;
  6.     protected String phoneNumber;
  7.     protected Address address;
  8.     protected Point point;
  9.     protected List<Review> reviews;
  10.     protected Long totalReviews;
  11.     protected Long totalRating;
  12.     protected List<String> images;
  13.     protected boolean hasCertificateOfExcellence;
  14.     protected String addedDate;
  15.     protected String lastModificationDate;
  17.     public Accomodation() {
  19.     }
  21.     public Accomodation(Accomodation accomodation) {
  22.     }
  24.     // 获取器和设置器方法
  25. }
英文:

These are my mondels:

  1. public class Accomodation {
  2.     ...
  3. }

and

  1. public class Attraction extends Accomodation {
  2.     ... 
  3.     private String openingTime;
  4. }

I have this method in my Controller class:

  1. protected Accomodation getAccomodationByFormData(CrudView crudView) {
  2.         Accomodation accomodation = new Accomodation();
  3.         // setters
  4.         return accomodation;
  5.     }

which is used within AttractionController (which extends previous Controller):

  1. @Override
  2.     protected Accomodation getAccomodationByFormData(CrudView crudView) {
  3.         Attraction attraction = (Attraction) super.getAccomodationByFormData(crudAttractionView);
  4.         attraction.setOpeningTime(getOpeningTimeWithFormData()); 
  5.         return attraction;
  6.     }

in another point of this AttractionController I have:

  1. ...
  2. Attraction attraction = (Attraction) getAccomodationByFormData(crudAttractionView); // throws ClassCastException
  3. ...

But this is giving me:

> Exception in thread "JavaFX Application Thread" java.lang.ClassCastException: class models.Accomodation cannot be cast to class models.Attraction (models.Accomodation and models.Attraction are in unnamed module of loader 'app')
at controllers.CrudAttractionController.getAccomodationByFormData(CrudAttractionController.java:302)
at controllers.CrudAttractionController.lambda$buttonConfermaClicked$4(CrudAttractionController.java:143)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Node.fireEvent(Node.java:8879)
at javafx.controls/javafx.scene.control.Button.fire(Button.java:200)
at javafx.controls/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:206)
at javafx.controls/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3851)
at javafx.graphics/javafx.scene.Scene$MouseHandler.access$1200(Scene.java:3579)
at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1849)
at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2588)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:397)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:434)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:390)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:433)
at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556)
at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942)
at javafx.graphics/com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11(GtkApplication.java:277)
at java.base/java.lang.Thread.run(Thread.java:834)

(Ps. Note that CrudAttractionView class extends CrudView)

  • How can I fix?

EDIT

Attraction

  1. public class Attraction extends Accomodation {
  2.     private String openingTime;
  4.     public Attraction() {
  6.     }
  8.     public Attraction(Accomodation accomodation) {
  9.         super(accomodation);
  10.     }
  12.     // getters and setters
  13. }

Accomodation

  1. public class Accomodation implements Serializable {
  2.     protected String id;
  3.     protected String name;
  4.     protected Integer avarageRating;
  5.     protected Integer avaragePrice;
  6.     protected String phoneNumber;
  7.     protected Address address;
  8.     protected Point point;
  9.     protected List&lt;Review&gt; reviews;
  10.     protected Long totalReviews;
  11.     protected Long totalRating;
  12.     protected List&lt;String&gt; images;
  13.     protected boolean hasCertificateOfExcellence;
  14.     protected String addedDate;
  15.     protected String lastModificationDate;
  17.     public Accomodation() {
  19.     }
  21.     public Accomodation(Accomodation accomodation) {
  22.     }
  24.     // getters and setters
  25. }

答案1

得分: 2

  1. 所有的 `Attraction` 都是 `Accomodation`，但并非所有的 `Accomodation` 都是 `Attraction`。
  3. 这意味着你不能安全地执行：
  5.     Attraction attraction = (Attraction) super.getAccomodationByFormData(crudAttractionView);
  7. 即使你在一个 `AttractionController` 中（Java 不会根据你控制器的名称更改 super.getAccomodation 的返回类型）。
  9. 一个不需要任何框架的解决方案是这样的：
  11.     Accomodation accomodation = super.getAccomodationByFormData(crudAttractionView);
  12.     Attraction attraction = new Attraction(accomodation);
  13.     attraction.setOpeningTime(getOpeningTimeWithFormData())
  15. 你只需要确保你有一个接受 `Accomodation` 的 `Attraction` 构造函数，并将其字段复制到你的景点。
  17. 类似于：
  19.     public Attraction(Accomodation accomodation){
  20.       attraction.setX(accomodation.getX())
  21.       ...
  22.     }
  24. 或者只是调用 `super(accomodation)`，并在 `Accomodation` 中有一个构造函数，可以将一个 `Accomodation` 复制到一个新的实例中（这样你将能够在所有未来的扩展类中使用该构造函数）
  26. 现在，确保你的 `accomodation` 实际上是一个 `Attraction`，然后进行类型转换。
  28. 在一个更简洁的例子中，以下是代码示例：
  30. ```java
  31. import java.io.Serializable;
  33. class Attraction extends Accomodation {
  35.     public Attraction() {
  37.     }
  39.     public Attraction(Accomodation accomodation) {
  40.         super(accomodation); // 让超类进行简单映射
  41.     }
  43.     // 获取器和设置器
  45.     public void setOpeningTime(String test){
  46.         //
  47.     }
  49.     protected Accomodation getAccomodationByFormData() {
  50.         Accomodation accomodation= new Accomodation();//super.getAccomodationByFormData(crudAttractionView);
  51.         Attraction attraction = new Attraction(accomodation); // 通过构造函数将我们的 accomodation 转换
  52.         attraction.setOpeningTime("..."); // 设置开放时间
  53.         return attraction;
  54.     }
  55. }
  57. class Accomodation implements Serializable {
  58.     protected String id;
  59.     protected String name;
  60.     protected Integer avarageRating;
  61.     protected Integer avaragePrice;
  62.     protected String phoneNumber;
  63.     protected Long totalReviews;
  64.     protected Long totalRating;
  65.     protected boolean hasCertificateOfExcellence;
  66.     protected String addedDate;
  67.     protected String lastModificationDate;
  69.     public Accomodation(Accomodation accomodation) {
  70.         this.id = accomodation.id;
  71.         this.name = accomodation.name;
  72.         this.avarageRating = accomodation.avarageRating;
  73.         this.avaragePrice = accomodation.avaragePrice;
  74.         this.phoneNumber = accomodation.phoneNumber;
  75.         this.totalReviews = accomodation.totalReviews;
  76.         this.totalRating = accomodation.totalRating;
  77.         this.hasCertificateOfExcellence = accomodation.hasCertificateOfExcellence;
  78.         this.addedDate = accomodation.addedDate;
  79.         this.lastModificationDate = accomodation.lastModificationDate;
  80.     }
  82.     public Accomodation() {
  84.     }
  86.     // 获取器和设置器
  87. }
英文:

All Attraction are Accomodation, but not all Accomodation are Attraction.

It means you cannot do safely :

  1. Attraction attraction = (Attraction) super.getAccomodationByFormData(crudAttractionView);

Even if you are in a AttractionController (java doesn't change the return type of super.getAccomadation based on your controller's name).

One solution without the need of any Framework would be to do something like :

  1. Accomodation accomodation = super.getAccomodationByFormData(crudAttractionView);
  2. Attraction attraction = new Attraction(accomodation);
  3. attraction.setOpeningTime(getOpeningTimeWithFormData())

You just have to make sure you have an Attraction Constructor that will take that Accomodation and copy it fields to your attraction.

Something like :

  1. public Attraction(Accomodation accomodation){
  2. attraction.setX(accomodation.getX())
  3. ...
  4. }

Or just calling super(accomodation) and having a Constructor in Accomodation that will be able to copy an Accomodation into a new one (so you'll be able to use that Constructor in all future extending classes)

Now, you ensure your accomodation is effectively an Attraction, then you cast it.

In a more concise example, here is what it would looks like

  1. import java.io.Serializable;
  2. class Attraction extends Accomodation {
  3. public Attraction() {
  4. }
  5. public Attraction(Accomodation accomodation) {
  6. super(accomodation); // we let super do the simple mapping
  7. }
  8. // getters and setters
  9. public void setOpeningTime(String test){
  10. //
  11. }
  12. protected Accomodation getAccomodationByFormData() {
  13. Accomodation accomodation= new Accomodation();//super.getAccomodationByFormData(crudAttractionView);
  14. Attraction attraction = new Attraction(accomodation); // we convert our accomodation thanks to our constructor
  15. attraction.setOpeningTime(&quot;...&quot;);
  16. return attraction;
  17. }
  18. }
  19. class Accomodation implements Serializable {
  20. protected String id;
  21. protected String name;
  22. protected Integer avarageRating;
  23. protected Integer avaragePrice;
  24. protected String phoneNumber;
  25. protected Long totalReviews;
  26. protected Long totalRating;
  27. protected boolean hasCertificateOfExcellence;
  28. protected String addedDate;
  29. protected String lastModificationDate;
  30. public Accomodation(Accomodation accomodation) {
  31. this.id = accomodation.id;
  32. this.name = accomodation.name;
  33. this.avarageRating = accomodation.avarageRating;
  34. this.avaragePrice = accomodation.avaragePrice;
  35. this.phoneNumber = accomodation.phoneNumber;
  36. this.totalReviews = accomodation.totalReviews;
  37. this.totalRating = accomodation.totalRating;
  38. this.hasCertificateOfExcellence = accomodation.hasCertificateOfExcellence;
  39. this.addedDate = accomodation.addedDate;
  40. this.lastModificationDate = accomodation.lastModificationDate;
  41. }
  42. public Accomodation() {
  43. }
  44. // getters and setters
  45. }

huangapple
  • 本文由 发表于 2020年10月1日 18:12:30
  • 转载请务必保留本文链接：https://go.coder-hub.com/64153266.html
  • classcastexception
  • java
  • polymorphism
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定