richdougherty opened a new pull request, #1435: URL: https://github.com/apache/commons-lang/pull/1435
This PR contains several new proposed methods to add to `ObjectUtils` that support chaining functions for objects which might be null. ## The Problem It's a very common pattern in Java to need to traverse a chain of method calls, where any link in the chain might be null. For example, `a.getB().getC().getD()`. Handling the null checks can be verbose. Other languages have built-in support for this, like Kotlin's safe navigation operator (`?.`), which allows for a concise `a?.b?.c?.d`. (See: https://en.wikipedia.org/wiki/Safe_navigation_operator) In Java, the two most common approaches are nested conditionals or using `Optional`. Using conditionals: ```java // Requires intermediate local variables to avoid multiple calls (e.g., to map.get) Person person = peopleMap.get(key); Pet pet = (person != null) ? person.getPet() : null; String petName = (pet != null) ? pet.getName() : null; ``` Using `Optional`: ```java // Idiomatic, but can be longer and requires intermediate object allocation String petName = Optional.ofNullable(peopleMap.get(key)) .map(Person::getPet) .map(Pet::getName) .orElse(null); ``` ## Proposed solution The proposed solution is to The basic idea is to add methods, e.g. `ObjectUtils.applyIfNotNull(...)`, with overloads for one, two, or three functions. Example with new method: ```java // Concise, single-line, and avoids extra allocations String petName = ObjectUtils.applyIfNotNull(peopleMap.get(key), Person::getPet, Pet::getName); ``` The methods check for null at each step of the function chain. If any value is null (either the initial input or the result of an intermediate function), the chain is short-circuited and null is returned immediately. ## Discussion - Happy to rename these if you have preferences for something else. I tried a few options, e.g. `mapNonNull` or `chain`, but this is what I settled on. - I did write `FailableFunction` versions as well, but in the end removed them to keep things simple to start with. ## Checklist <!-- Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at https://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --> Thanks for your contribution to [Apache Commons](https://commons.apache.org/)! Your help is appreciated! Before you push a pull request, review this list: - [x] Read the [contribution guidelines](CONTRIBUTING.md) for this project. - [x] Read the [ASF Generative Tooling Guidance](https://www.apache.org/legal/generative-tooling.html) if you use Artificial Intelligence (AI). - [x] I used AI to create any part of, or all of, this pull request. - [x] Run a successful build using the default [Maven](https://maven.apache.org/) goal with `mvn`; that's `mvn` on the command line by itself. - [x] Write unit tests that match behavioral changes, where the tests fail if the changes to the runtime are not applied. This may not always be possible, but it is a best-practice. - [x] Write a pull request description that is detailed enough to understand what the pull request does, how, and why. - [x] Each commit in the pull request should have a meaningful subject line and body. Note that a maintainer may squash commits during the merge process. ## Comments - I've previously signed the CLA - my Apache username is `[email protected]`. Or you can see me on the contributor list here: https://commons.apache.org/proper/commons-collections/team.html - Generative AI was used for code review, not coding. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
