java Lombok@Data annotation项目是否创建了任何类型的构造函数？

Question

我有一个带有@Data注释的类，但我不确定是生成了带参数的构造函数，还是生成的唯一构造函数是vanilla Java中的默认构造函数（无参数）

Answer 1

如果没有定义构造函数，将生成@RequiredArgsConstructor

该Project Lombok @Data page说明：

@Data is like having implicit @Getter, @Setter, @ToString, @EqualsAndHashCode and @RequiredArgsConstructor annotations on the class (except that no constructor will be generated if any explicitly written constructor exists).

Answer 2

@Data仅在创建@RequiredArgsConstructor。Lombok的Data annotation和constructors文档站点解释：

@RequiredArgsConstructor generates a constructor with 1 parameter for each field that requires special handling. All non-initialized final fields get a parameter, as well as any fields that are marked as @NonNull that aren't initialized where they are declared. For those fields marked with @NonNull, an explicit null check is also generated. The constructor will throw a NullPointerException if any of the parameters intended for the fields marked with @NonNull contain null. The order of the parameters match the order in which the fields appear in your class.

假设您有一个使用Lombok@Data注释的POJO：

public @Data class Z {
    private String x;
    private String y;
}

无法将对象创建为Z z = new Z(x, y);，因为Z类上没有“必需”的参数。它使用零参数创建构造函数，因为@Data为您的属性提供setter和getter，您可以在创建实例后调用setX和setY

您可以将x和y设置为@NonNull或final，以便它们必须通过构造函数传递，或者使用@allargsconstuctor注释类Z