Java获取泛型实际类型的方法详解

public abstract class TestClass<E> {
  ......
}

public class TestStringClass extends TestClass<String>{
  ....
}

public class TestIntegerClass extends TestClass<Integer>{
  ....
}
....

Type genericSuperclass = this.getClass().getGenericSuperclass();
if (genericSuperclass instanceof ParameterizedType){
  ParameterizedType parameterizedType = (ParameterizedType) genericSuperclass;
  Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
  for (Type actualTypeArgument : actualTypeArguments) {
    System.out.println(actualTypeArgument);
  }
}

public abstract class TestClass<E> {

   public void print(){
      Type genericSuperclass = this.getClass().getGenericSuperclass();
      List<Type> list = null;
      if (genericSuperclass instanceof ParameterizedType){
         ParameterizedType parameterizedType = (ParameterizedType) genericSuperclass;
         Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
         list = Arrays.asList(actualTypeArguments);
      }
      System.out.println(this.getClass() + " 的泛型 = " + list);
   }
}

public class TestStringClass extends TestClass<String>{

    public static void main(String[] args) {
        TestStringClass testStringClass = new TestStringClass();
        testStringClass.print();
    }
}

// class xxx.TestStringClass 的泛型 = [class java.lang.String]

public class TestMapClass extends TestClass<Map<String,String>>{

    public static void main(String[] args) {
        TestMapClass testMapClass = new TestMapClass();
        testMapClass.print();
    }
}

// class xxx.TestMapClass 的泛型 = [java.util.Map<java.lang.String, java.lang.String>]

private HashMap<Integer, List<String>> myMap;
 
  public void example() {
      ResolvableType t = ResolvableType.forField(getClass().getDeclaredField("myMap"));
      t.getSuperType(); // AbstractMap<Integer, List<String>>
      t.asMap(); // Map<Integer, List<String>>
    	// 获取指定下标的泛型类型
      t.getGeneric(0).resolve(); // Integer
      t.getGeneric(1).resolve(); // List
      t.getGeneric(1); // List<String>
    	// 获取指定下标的泛型的指定下标的泛型，即获取嵌套泛型的泛型
      t.resolveGeneric(1, 0); // String
  }