Java:避免在嵌套类中检查空值(深度空值检查) [英] Java: avoid checking for null in nested classes (Deep Null checking)

问题描述

想象一下，我有一个家庭班级.它包含一个人员列表.每个(类)Person 包含一个(类)地址.每个(类)地址都包含一个(类)邮政编码.任何中间"类可以为空.

Imagine I have a class Family. It contains a List of Person. Each (class) Person contains a (class) Address. Each (class) Address contains a (class) PostalCode. Any "intermediate" class can be null.

那么，有没有一种简单的方法可以访问 PostalCode，而不必在每一步都检查 null?即，有没有办法避免以下菊花链代码?我知道没有本地"Java 解决方案，但希望有人知道图书馆或其他东西.(检查 Commons & Guava 并没有看到任何东西)

So, is there a simple way to get to PostalCode without having to check for null in every step? i.e., is there a way to avoid the following daisy chaining code? I know there's not "native" Java solution, but was hoping if anyone knows of a library or something. (checked Commons & Guava and didn't see anything)

if(family != null) {
    if(family.getPeople() != null) {
        if(family.people.get(0) != null) {
            if(people.get(0).getAddress() != null) {
                if(people.get(0).getAddress().getPostalCode() != null) {
                    //FINALLY MADE IT TO DO SOMETHING!!!
                }
            }
        }
    }
}

不，不能改变结构.它来自我无法控制的服务.

No, can't change the structure. It's from a service I don't have control over.

不，我不能使用 Groovy，它很方便，Elvis"；操作员.

No, I can't use Groovy and it's handy "Elvis" operator.

不，我不想等待 Java 8 :D

No, I'd prefer not to wait for Java 8 :D

我不敢相信我是有史以来第一个厌倦编写这样的代码的开发人员，但我一直找不到解决方案.

I can't believe I'm the first dev ever to get sick 'n tired of writing code like this, but I haven't been able to find a solution.

推荐答案

您可以用于:

product.getLatestVersion().getProductData().getTradeItem().getInformationProviderOfTradeItem().getGln();

可选等价物:

Optional.ofNullable(product).map(
            Product::getLatestVersion
        ).map(
            ProductVersion::getProductData
        ).map(
            ProductData::getTradeItem
        ).map(
            TradeItemType::getInformationProviderOfTradeItem
        ).map(
            PartyInRoleType::getGln
        ).orElse(null);

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