Java的泛型反射

Posted 2020-08-21 winters1992

If the superclass is a parameterized type, the {@code Type}
     * object returned must accurately reflect the actual type
     * parameters used in the source code. T

上文档DOC，如果父类是一个参数化类型，那么Type返回的是参数类型的真实类型

 

package entity;


import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

/**
 * Created by Administrator on 2016/11/27 0027.
 */
public class BaseDaoImpl<T> implements BaseDao<T> {

    public BaseDaoImpl(){
        Type type = getClass().getGenericSuperclass();
        Type[] params = ((ParameterizedType)type).getActualTypeArguments();
        System.out.println((Class<T>)params[0]);
    }

    public T findByid(int id) {
        return null;
    }
}

package entity;

/**
 * Created by Administrator on 2016/11/27 0027.
 */
public class UserDaoImpl extends BaseDaoImpl<User> {
}

package entity;

/**
 * Created by Administrator on 2016/11/27 0027.
 */
public interface BaseDao<T> {
   public T findByid(int id);
}

package entity;

import org.junit.Test;

/**
 * Created by Administrator on 2016/11/27 0027.
 */
public class GenericTest {
    @Test
    public void testGeneric(){
        UserDaoImpl baseDao = new UserDaoImpl();
        //BaseDaoImpl<User> baseDao1 = new BaseDaoImpl<User>();
    }
}

 

记录总结，只有继承的父类为参数化类型，此时反射的

ParameterizedType 才能拿到参数类型