java - 以内部类作为参数的Spring Controller

Question

我有一个 Spring Controller ，其方法映射到请求:

@RequestMapping(value = "/album", method = RequestMethod.POST)
public void generateAlbum(GenerateAlbumParams params, HttpServletResponse response){
...
}

GenerateAlbumParams 是一个简单的类:

@Getter
@Setter
public class GenerateAlbumParams {

    public enum Position {LEFT_TOP, LEFT_BOTTOM, RIGHT_TOP, RIGHT_BOTTOM}
    private List<SlideParams> slideParams = new ArrayList<>();
}

和SlideParams是:

@Getter
@Setter
public class SlideParams{
    private Boolean checked = false;
    private Long id;
    private GenerateAlbumParams.Position mapLegendPosition;
    private GenerateAlbumParams.Position mapTablePosition;
}

一切正常，但如果我想将 SlideParams 作为 GenerateAlbumParams 的内部类:

@Getter
@Setter
public class GenerateAlbumParams {

    public enum Position {LEFT_TOP, LEFT_BOTTOM, RIGHT_TOP, RIGHT_BOTTOM}
    private List<SlideParams> slideParams = new ArrayList<>();

    @Getter
    @Setter
    public class SlideParams{
        private Boolean checked = false;
        private Long id;
        private Position mapLegendPosition;
        private Position mapTablePosition;
    }
}

它抛出一个异常:

HTTP Status 500 - Request processing failed; nested exception is org.springframework.beans.InvalidPropertyException: Invalid property 'slideParams[0]' of bean class [xxx.GenerateAlbumParams]: Illegal attempt to get property 'slideParams' threw exception; nested exception is org.springframework.beans.NullValueInNestedPathException: Invalid property 'slideParams' of bean class [xxx.GenerateAlbumParams]: Could not instantiate property type [xxx.GenerateAlbumParams$SlideParams] to auto-grow nested property path; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [xxx.GenerateAlbumParams$SlideParams]: Is it an abstract class?; nested exception is java.lang.InstantiationException: xxx.GenerateAlbumParams$SlideParams

Answer 1

似乎你应该让你的内部类static这样它就可以在不引用外部类的任何对象的情况下被实例化(例如new GenerateAlbumParams.SlideParams()