java - Spring BeanUtils 无法实例化泛型类

Question

我正在尝试实现一些在我的实体和 DTO 之间进行转换的东西。

我有 DTO 的基类(称为模型):

public class BaseModel<Entity> implements Model<Entity> {

    @Override
    public Entity toEntity(Class<Entity> entityClass) {
        Entity entityInstance = BeanUtils.instantiate(entityClass);
        BeanUtils.copyProperties(this, entityInstance);
        return entityInstance;
    }
}

但是以下测试未通过:

public class BaseModelTest {

    @Entity
    public class SomeEntity {
        @Id
        private Long id;
        private String name;

        public SomeEntity() {
        }

        public SomeEntity(Long id, String name) {
            this.id = id;
            this.name = name;
        }

        public Long getId() {
            return id;
        }

        public String getName() {
            return name;
        }
    }

    @Test
    public void toEntity_givenEntityClass_shouldCreateNewInstance() throws Exception {
        //given
        BaseModel<SomeEntity> model = new BaseModel();

        //when
        SomeEntity entity = model.toEntity(SomeEntity.class);

        //then
        assertNotNull(entity);
    }
}

我遇到了异常:(尽管事实上，在调试器下我看到了所有的ctors):

org.springframework.beans.BeanInstantiationException: Failed to instantiate [package.BaseModelTest$SomeEntity]: Is it an abstract class?; nested exception is java.lang.InstantiationException: package.BaseModelTest$SomeEntity

Caused by: java.lang.InstantiationException: package.BaseModelTest$SomeEntity
Caused by: java.lang.NoSuchMethodException: package.BaseModelTest$SomeEntity.<init>()

Answer 1

当前，要创建新的 SomeEntity 实例，您需要一个封闭的 BaseModelTest 类的实例。 SomeEntity 应该是一个内部静态类。替换:

public class SomeEntity {

与

public static class SomeEntity {

顺便说一句。如果 DTO 类将 1-1 映射到模型类，那么它就没有任何意义，它不会添加任何值，它只是样板代码。