java 反射之泛型

由于java 泛型擦除机制，无法通过反射直接获取泛型的类型。但是，Java反射可以通过class获取父类泛型类型
泛型被擦除Demo：

public class Test {

    public static void main(String[] args) throws Exception {
        List<Integer> integerList=new ArrayList();
        integerList.add(1);
        //泛型被擦除
        integerList.getClass().getMethod("add",Object.class).invoke(integerList,"test");
        //会打印出test
        System.out.println(integerList.get(1));
    }
}

通过反射获取父类的泛型类型 Demo
Dao.java

public abstract class Dao<T> {

    public T get(Long id) {
        return null;
    }

    public T save(T data) {
        return null;
    }
}

StudentDao.java

public class StudentDao extends Dao<Student>{
}

public class Test {

    public static void main(String[] args) throws Exception {
        StudentDao studentDao = new StudentDao();
        Class clszz = getSuperClassGenericType(studentDao.getClass(), 0);
      //打印出泛型类型
        System.out.println(clszz);
    }

    public static Class getSuperClassGenericType(Class clazz, int index) {
        if (clazz == null || index < 0) {
            return Object.class;
        }
        Type genType = clazz.getGenericSuperclass();
        if (!(genType instanceof ParameterizedType)) {
            return Object.class;
        }
        Type[] params = ((ParameterizedType) genType).getActualTypeArguments();
        if (params == null || params.length <= index) {
            return Object.class;
        }
        if (!(params[index] instanceof Class)) {
            return Object.class;
        }
        return (Class) params[index];
    }
}