从java中的对象获取类列表

Question

我目前正在尝试创建一个不同的List<Class> classList，其中包含一个对象的所有类，例如

DemoObject.java

public class DemoObject {

    private Integer id;

    private String name;

    private BigDecimal price;

    private Boolean isActive;

    private List<NestedDemoObject> nested;

}

NestedDemoObject.java

public class NestedDemoObject {

    private Integer id;

    private String nameNest;

    private Boolean isActive;

}

我想要创建的是一个方法public List<Class> getDistinctClasses(Class cl);，例如您将其作为输入DemoObject.class并返回一个列表

[DemoObject.class, Integer.class, String.class, BigDecimal.class, Boolean.class, List.class, NestedDemoObject.class]

另一个例子NestedDemoObject.class是

[NestedDemoObject.class, Integer.class, String.class, Boolean.class]

我试图使用.getDeclaredClasses()fromClass没有任何运气。有什么方法可以使用反射 API 从对象中获取所有嵌套类？

任何帮助或方向表示赞赏。

Answer 1

Mark 提供的解决方案是部分正确的。您正在尝试从声明的字段中检索类的正确方法。然而，getType()方法并没有揭示泛型类型。为了访问您应该使用的泛型类型Field.getGenericType()。它将类作为Type对象返回。该Field对象知道自己的类型（它们也不会被删除作为一个可能会误认为）。这是一个用泛型打印类型的 java 1.8+ 示例：Arrays.stream(DemoObject.class.getDeclaredFields())&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .map(Field::getGenericType)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .map(Type::getTypeName)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .distinct()&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .forEach(System.out::println);它将打印以下结果：java.lang.Integerjava.lang.Stringjava.math.BigDecimaljava.lang.Booleanjava.util.List<com.eto.sandbox.NestedDemoObject>如果您想使用泛型类型或出于任何原因解析它们，那么您可以使用以下示例：&nbsp;Arrays.stream(DemoObject.class.getDeclaredFields())&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .map(Field::getGenericType)&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .distinct()&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .forEach(type -> {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (type instanceof Class) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // This is a simple class&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; } else if (type instanceof ParameterizedType) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // This is a generic type. You can parse its parameters recursively.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; });

Answer 2

也许这为您指明了正确的方向：for (Field f : DemoObject.class.getDeclaredFields()) {&nbsp; &nbsp; System.out.println(f.getType().getName());}这打印：java.lang.Integerjava.lang.Stringjava.math.BigDecimaljava.lang.Booleanjava.util.List您可以通过类似Class.forName.我觉得很奇怪，这getDeclaredClasses对我也不起作用，我会调查一下。当我知道更多时，我会更新答案。更新getDeclaredClasses 打印在类中定义的类，如下所示：class DemoObject {&nbsp; &nbsp; private Integer id;&nbsp; &nbsp; private String name;&nbsp; &nbsp; private BigDecimal price;&nbsp; &nbsp; private Boolean isActive;&nbsp; &nbsp; private List<NestedDemoObject> nested;&nbsp; &nbsp; public class InnerClass {&nbsp; &nbsp; }}然后执行getDeclaredClasses：for (Class<?> f : DemoObject.class.getDeclaredClasses()) {&nbsp; &nbsp; System.out.println(f.getName());}打印值：DemoObject$InnerClass