测试结构

@Data
@NoArgsConstructor
@AllArgsConstructor
public class SuperClass {
    private long id;
    private String name;
}

@Data
@ToString(callSuper = true)
public class SubClass extends SuperClass {
}

转换

• 1）直接转换

public class TestMain {
    public static void main(String[] args) {
        SuperClass superClass = new SuperClass(1, "name");
        SubClass subClass = (SubClass) superClass;
        System.out.println(subClass);
    }
}

出现如下异常：

Exception in thread "main" java.lang.ClassCastException: org.company.cast.SuperClass cannot be cast to org.company.cast.SubClass
    at org.company.TestMain.main(TestMain.java:9)

• 2）序列化反序列化

需引入 Jackson 依赖，可参考 Jackson 使用简介 。

public class TestMain {
    public static void main(String[] args) {
        SuperClass superClass = new SuperClass(1, "name");
        String serialize = serialize(superClass);
        SubClass subClass = deserialize(serialize, SubClass.class);
        System.out.println(subClass);
    }

    private static final ObjectMapper objectMapper = new ObjectMapper();

    @SneakyThrows
    public static String serialize(Object obj) {
        return objectMapper.writeValueAsString(obj);
    }

    @SneakyThrows
    public static <T> T deserialize(String json, Class<T> clazz) {
        return objectMapper.readValue(json, clazz);
    }
}

控制台输出：

SubClass(super=SuperClass(id=1, name=name))

• 3）BeanUtils.copyProperties

使用的是 Spring 的 spring-beans 版本。

public class TestMain {
    public static void main(String[] args) {
        SuperClass superClass = new SuperClass(1, "name");

        SubClass subClass = new SubClass();
        BeanUtils.copyProperties(superClass, subClass);
        System.out.println(subClass);
    }
}

控制台输出：

SubClass(super=SuperClass(id=1, name=name))

API 差异

• Spring spring-beans 版本：源对象 source 在前面，目标对象 target 在后面。

package org.springframework.beans;

public abstract class BeanUtils {
    public static void copyProperties(Object source, Object target) throws BeansException {
}

• Apache commons-beanutils 版本：源对象 orig 在后面，目标对象 dest 在前面。

package org.apache.commons.beanutils;

public class BeanUtils {
    public static void copyProperties(final Object dest, final Object orig)
}

参考

• How to cast parent into child in Java