java Lombok 中带有 @Builder 或 @Getter 注释的默认字段值
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Default field value with @Builder or @Getter annotation in Lombok
提问by Hazel Troost
I'm using Lombok @Builderannotation, but I'd like some of the Stringfields to be optional and default to ""to avoid NPEs. Is there an easy way to do this? I can't find anything.
我正在使用 Lombok@Builder注释，但我希望某些String字段是可选的并且默认""为避免 NPE。是否有捷径可寻？我找不到任何东西。
Alternately, a way to customize @Getterto return a default value if the variable is null.
或者，@Getter如果变量是null.
采纳答案by JafarKhQ
Starting from version v1.16.16they added @Builder.Default.
从v1.16.16他们添加的版本开始@Builder.Default。
@Builder.Defaultlets you configure default values for your fields when using@Builder.
@Builder.Default允许您在使用@Builder.
example:
例子：
@Setter
@Getter
@Builder
public class MyData {
private Long id;
private String name;
@Builder.Default
private Status status = Status.NEW;
}
PS:Nice thing they also add warning in case you didn't use @Builder.Default.
PS：好在他们还添加了警告，以防您没有使用@Builder.Default.
Warning:(35, 22) java: @Builder will ignore the initializing expression entirely. If you want the initializing expression to serve as default, add @Builder.Default. If it is not supposed to be settable during building, make the field final.
警告:(35, 22) java: @Builder 将完全忽略初始化表达式。如果您希望初始化表达式用作默认值，请添加@Builder.Default。如果它不应该在构建过程中设置，请将字段设为 final。
回答by ntalbs
You have to provide the builder class like the below:
您必须提供如下所示的构建器类：
@Builder
public class XYZ {
private String x;
private String y;
private String z;
private static class XYZBuilder {
private String x = "X";
private String y = "Y";
private String z = "Z";
}
}
Then the default value for x, y, zwill be "X", "Y", "Z".
那么x, y,的默认值z将是"X", "Y", "Z"。
回答by JeanValjean
Another way to go is to use @Builder(toBuilder = true)
另一种方法是使用 @Builder(toBuilder = true)
@Builder(toBuilder = true)
public class XYZ {
private String x = "X";
private String y = "Y";
private String z = "Z";
}
and then you use it as follows:
然后按如下方式使用它：
new XYZ().toBuilder().build();
With respect to the accepted answer, this approach is less sensible to class renaming. If you rename XYZbut forget to rename the inner static class XYZBuilder, then the magic is gone!
关于公认的答案，这种方法对类重命名不太明智。如果您重命名XYZ但忘记重命名内部静态类XYZBuilder，那么魔法就消失了！
It's all up to to you to use the approach you like more.
使用您更喜欢的方法完全取决于您。
