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Java:深度克隆/复制实例的推荐解决方案

分类: 技术问答 • 2022-06-13 20:32:31
问题描述：

我想知道是否有推荐的方法在 Java 中进行实例的深度克隆/复制.

I'm wondering if there is a recommended way of doing deep clone/copy of instance in java.

我有 3 个解决方案，但我可能会错过一些，我想听听您的意见

I have 3 solutions in mind, but I can have miss some, and I'd like to have your opinion

包括 Bohzo 命题并改进问题:它更多地是关于深克隆而不是浅克隆.

edit: include Bohzo propositon and refine question: it's more about deep cloning than shallow cloning.

在属性之后手动对克隆进行编码，并检查是否也克隆了可变实例.
专业:
- 控制将要执行的操作
- 快速执行
缺点:
- 编写和维护繁琐
- 容易出错(复制/粘贴失败、缺少属性、重新分配可变属性)

code the clone by hand properties after properties and check that mutable instances are cloned too.
pro:
- control of what will be performed
- quick execution
cons:
- tedious to write and maintain
- bug prone (copy/paste failure, missing property, reassigned mutable property)

使用您自己的反射工具或外部帮助程序(如 jakarta common-beans)，很容易编写一个通用的复制方法，该方法将在一行中完成工作.
专业:
- 易于编写
- 无需维护
缺点:
- 减少对发生的事情的控制
- 如果反射工具也没有克隆子对象，则可变对象容易出错
- 执行速度较慢

With your own reflection tools or with an external helper (like jakarta common-beans) it is easy to write a generic copy method that will do the job in one line.
pro:
- easy to write
- no maintenance
cons:
- less control of what happens
- bug prone with mutable object if the reflection tool does not clone sub objects too
- slower execution

使用适合您的框架，例如:
commons-lang序列化实用程序
Java 深度克隆库
推土机
Kryo

Use a framework that do it for you, like :
commons-lang SerializationUtils
Java Deep Cloning Library
Dozer
Kryo

专业:
- 与反射相同
- 更好地控制将要克隆的内容.
缺点:
- 每个可变实例都被完全克隆，即使在层次结构的末尾
- 执行起来可能很慢

pro:
- same as reflection
- more control over what will be exactly be cloned.
cons:
- every mutable instance is fully cloned, even at the end of the hierarchy
- could be very slow to execute

javassit、BCEL 或 cglib 可用于生成专用克隆器像一只手写的一样快.有人知道为此目的使用这些工具之一的库吗?

javassit, BCEL or cglib might be use to generate a dedicated cloner as fast as one hand writed. Someone knows a lib using one of these tools for this purpose ?

我在这里错过了什么?
你会推荐哪一个?

What I have missed here ?
Which one would you recommend ?

谢谢.

答

对于深度克隆(克隆整个对象层次结构):

  • commons-lang SerializationUtils - 使用序列化 - 如果所有类都在你的控制之下，你可以强制实现 Serializable.

    For deep cloning (clones the entire object hierarchy):

    • commons-lang SerializationUtils - using serialization - if all classes are in your control and you can force implementing Serializable.

      Java 深度克隆库 - 使用反射 - 在类或对象的情况下您想要克隆不受您的控制(第 3 方库)并且您不能让它们实现 Serializable，或者在您不想实现 Serializable 的情况下.

      Java Deep Cloning Library - using reflection - in cases when the classes or the objects you want to clone are out of your control (a 3rd party library) and you can't make them implement Serializable, or in cases you don't want to implement Serializable.

      • commons-beanutils BeanUtils - in most cases.

      Spring BeanUtils - 如果你已经在使用 spring，因此在类路径上有这个实用程序.

      Spring BeanUtils - if you are already using spring and hence have this utility on the classpath.

      我故意省略了自己动手"选项 - 上面的 API 提供了对克隆什么和不克隆什么的良好控制(例如使用 transient 或 String[] ignoreProperties)，所以重新发明轮子不是首选.

      I deliberately omitted the "do-it-yourself" option - the API's above provide a good control over what to and what not to clone (for example using transient, or String[] ignoreProperties), so reinventing the wheel isn't preferred.

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