Lombok @Builder未初始化集合 [英] Lombok @Builder not initializing collections

问题描述

我正在使用Lombok的 @Data 和 @Builder 注释，如下所示:

I am using Lombok's @Data and @Builder annotations like this:

@Data
@Builder(toBuilder = true)
class Movie {

    // Some other fields here.

    private final List<Actor> actors;

}

当我使用构建器创建新的 Movie 而不指定任何参与者时，我希望Lombok将我的列表初始化为 Collections.emptyList().但这不会发生:

When I create a new Movie using the builder, without specifying any actors, I would expect Lombok to initialize my List to Collections.emptyList(). But this does not happen:

List<Actor> actors = Movie.builder().build().getActors();
System.out.println(actors); // Prints 'null'.

在 @Builder 批注的文档中，在Vanilla Java的代码示例( https://projectlombok.org/features/Singular-snippet.html ).在此处的Vanilla Java示例的第112行，似乎列表应该初始化为空列表.

In the documentation for the @Builder annotation, it is stated at line 55 and 56 in the code-example for Vanilla Java (https://projectlombok.org/features/Builder.html) that I should look at the code example for @Singular (https://projectlombok.org/features/Singular-snippet.html). At line 112 in the Vanilla Java example here, it seems like the list should be initialized to the empty list.

我检查了一下，如果我用 @Singular 注释列表，确实会发生这种情况:

I checked, and it does indeed happen if I annotate the list with @Singular:

@Data
@Builder(toBuilder = true)
class Movie {

    // Some other fields here.

    @Singular
    private final List<Actor> actors;

}

List<Actor> actors = Movie.builder().build().getActors();
System.out.println(actors); // Prints '[]'.

这是Lombok中的错误，还是我做错了什么?根据文档，似乎在两种情况下都应将列表初始化为空列表(因为 @Builder 文档是指 @Singular 文档).

Is this a bug in Lombok, or is there something that I am doing wrong? According to the documentation, it seems like the list should be initialized to the empty list in both cases (because the @Builder doc refers to the @Singular doc).

推荐答案

仅当使用 @Singular 时，您会得到一个空列表.在构建器文档页面上，它说:

Only when you use @Singular, you get an empty list. On the Builder documentation page it says:

…带有 @Singular 批注，lombok会将该构建器节点视为一个集合.

…with the @Singular annotation, lombok will treat that builder node as a collection.

在没有 @Singular 的情况下，lombok将其视为任何其他对象.因此它将是 null 而不是空的Collection.

Without the @Singular, lombok treats it as any other object. So it will be null instead of an empty Collection.

披露:我是Lombok开发人员

Disclosure: I am a Lombok developer

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