Generics have been erased after compilation. The jvm cannot see the generic information at all. This is due to historical reasons, so the p.getClass you mentioned cannot exist

The first question is a good idea, but as far as I know it cannot be implemented. The object cannot know the status of the subclass. Java's polymorphic mechanism can only query methods from the parent class or parent interface.

I guess the first question you think you can get the member variables of a subclass is that once the toString method of the subclass is executed after inheritance, your own this will also be called, which is wrong. At run time, the jvm will obtain this method from the object space of the parent class and execute it. So, no matter what, they are just member variables of the parent class

I made a mistake in the above italicized part. After running the IDE to test it, I found that I was wrong about what I understood before. I hope it didn’t cause trouble to the questioner.
The code posted below can loop to obtain all variables from the subclass to the parent class. Hope it helps

public String toString() { StringBuilder sb = new StringBuilder(); Class clazz = this.getClass(); while(clazz.getSuperclass() != null){ Field[] fields = clazz.getDeclaredFields(); try { for (Field field : fields) { field.setAccessible(true); sb.append(field.getName()).append("=").append(field.get(this)) .append("\n"); } } catch (Exception e) { e.printStackTrace(); } clazz = clazz.getSuperclass(); } return sb.toString(); }

Reflection tool class

package cn.hylexus.app.util; import java.lang.reflect.Field; import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class ReflectionUtils { public static List getFields(Class clz) { List ret = new ArrayList<>(); for (Class c = clz; c != Object.class; c = c.getSuperclass()) { Field[] fields = c.getDeclaredFields(); ret.addAll(Arrays.asList(fields)); } return ret; } /** * @param cls * 子类对应的Class * @param index * 子类继承父类时传入的索引,从0开始 * @return */ public static Class getSuperClassGenericType(Class cls, int index) { if (index < 0) return null; Type type = cls.getGenericSuperclass(); if (!(type instanceof ParameterizedType)) return null; ParameterizedType parameterizedType = (ParameterizedType) type; Type[] typeArguments = parameterizedType.getActualTypeArguments(); if (typeArguments == null || typeArguments.length == 0 || index > typeArguments.length - 1) return null; Type t = typeArguments[index]; if (!(t instanceof Class)) { return null; } return (Class) t; } public static Class getSuperClassGenericType(Class cls) { return getSuperClassGenericType(cls, 0); } }

Question 1

public class RequestInfo { @Override public String toString() { StringBuilder sb = new StringBuilder(); //可以拿到多层次基础的属性 List fields = ReflectionUtils.getFields(this.getClass()); for (Field f : fields) { f.setAccessible(true); try { sb.append(f.getName()).append("=").append(f.get(this)).append("\n"); } catch (Exception e) { e.printStackTrace(); } } return sb.toString(); } }

Question 2

@SuppressWarnings("unchecked") protected void init() { logTag = getClass().getSimpleName(); try { //这里可以拿到动态绑定的Class信息 Class clz = ReflectionUtils.getSuperClassGenericType(this.getClass(), 1); respBean = (P) clz.newInstance(); } catch (Exception e) { e.printStackTrace(); } }

The first question can be solved using commons-beanutils.