Lombok - the wrong way

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id="page-container"><section id="content" role="main" class="main-content content--lombok-the-wrong-way"><section class="content__section section-post"><div class="viewport"><div class="post__grid grid--content"><article class="post__content text--rich" role="main" data-blog-post="" data-submenu="" data-submenu_h1="data-submenu_h2="><div class="title-area"><h1 class="banner__title">Lombok - the wrong way</h1><div class="taxonomy__tags"><ul class="article__tags tags__list"><li class="list__item item--tag"><a href="/blog/?tag=java" class="no-border">Java</a></li><li class="list__item item--tag"><a href="/blog/?tag=software engineering" class="no-border">Software Engineering</a></li><li class="list__item item--tag"><a href="/blog/?tag=lombok" class="no-border">Lombok</a></li></ul></div><div class="block-author author--big"><div class="grid--two-columns"><div class="author__meta"><a href="/blog/?author=Łukasz%20Lenart"><figure alt="webp image" class="employee__image" style="background-image:url('/user/webp/user/themes/softwaremill/assets/team/IFEnlXzvQ7ci5C3.webp')"/></a><div class="author__desc"><p class="name"><a href="/blog/?author=Łukasz%20Lenart">Łukasz Lenart</a></p><p><span class="date">02 Feb 2022.</span><span class="time-to-read">6 minutes read</span></p></div></div><div class="author__social-media"><div class="author__socialmedia block-socialmedia"><ul class="socialmedia__list"><li><a target="_blank" href="https://www.linkedin.com/in/lukaszlenart"><figure class="socialmedia__ico ui-ico ico--black ico--linkedin"><svg version="1.1" class="ico-linkedin" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewbox="-949 471.7 20.9 19.3" enable-background="new -949 471.7 20.9 19.3" xml:space="preserve"><rect class="svg__ico" x="-948.5" y="477.9" fill="#FFFFFF" width="4.1" height="13"/><path class="svg__ico" fill="#FFFFFF" 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c0,0.4,0.1,0.8,0.2,1.2c-4-0.2-7.8-2.1-10.3-5.2c-1.3,2.3-0.6,5.3,1.6,6.8c-0.8,0-1.6-0.2-2.2-0.7v0.1c0,2.4,1.7,4.5,4.1,5 c-0.4,0.1-0.9,0.2-1.3,0.2c-0.3,0-0.6,0-0.9-0.1c0.6,2.1,2.6,3.5,4.7,3.5c-1.8,1.4-4,2.1-6.2,2.2c-0.4,0-0.8,0-1.2-0.1 c2.3,1.5,5,2.2,7.7,2.2c9.3,0,14.3-7.7,14.3-14.4V476c0.8-0.8,1.6-1.8,2.2-2.7c-0.9,0.4-1.9,0.7-2.9,0.8 C-924.6,473.4-923.8,472.4-923.4,471.2z"/></svg></figure></a></li><li><a target="_blank" href="https://github.com/lukaszlenart"><figure class="socialmedia__ico ui-ico ico--black ico--github"><svg version="1.1" class="ico-github" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" viewbox="-946 469 25.9 25" enable-background="new -946 469 25.9 25" xml:space="preserve"><path class="svg__ico" fill="#FFFFFF" d="M-933.2,469c-7.1,0-12.8,5.8-12.8,12.8c0,5.5,3.6,10.4,8.8,12.1c0.7,0.1,0.9-0.3,0.9-0.6v-2.2 c-3.6,0.8-4.3-1.7-4.3-1.7c-0.2-0.8-0.7-1.5-1.4-1.9c-1.2-0.8,0.1-0.7,0.1-0.7c0.8,0.1,1.6,0.6,2,1.3c0.7,1.3,2.3,1.8,3.6,1.1 c0,0,0.1,0,0.1,0c0-0.7,0.3-1.3,0.8-1.7c-2.8-0.3-5.8-1.4-5.8-6.3c0-1.3,0.4-2.5,1.3-3.4c-0.4-1.1-0.4-2.3,0.2-3.4 c0,0,1.1-0.3,3.5,1.3c1.1-0.3,2.1-0.4,3.2-0.4c1.1,0,2.2,0.2,3.2,0.4c2.4-1.7,3.5-1.3,3.5-1.3c0.4,1.1,0.5,2.3,0.2,3.4 c0.9,0.9,1.3,2.1,1.3,3.4c0,4.9-3,6-5.8,6.3c0.6,0.6,0.9,1.5,0.8,2.4v3.5c0,0.3,0.2,0.8,0.9,0.6c5.2-1.8,8.7-6.6,8.7-12.2 C-920.3,474.7-926.1,469.1-933.2,469z"/></svg></figure></a></li></ul></div></div></div></div></div><p><img src="/user/webp/user/themes/softwaremill/assets/img/post-image/7xWqh4wzFnYgUdj.webp" alt="Lombok - the wrong way webp image"/></p><div><p>I’ve been using the <a href="https://www.scala-lang.org/">Scala language</a> for a couple of years, yet I decided to join a new project written purely in Java as I was curious what new and interesting had happened in the Java ecosystem during these years. It’s also a totally new kind of problems to solve as the main purpose of the project is to help companies resolve the <a href="https://en.wikipedia.org/wiki/Vehicle_routing_problem">Vehicle Routing Problem</a> — VRP in short.</p><p>Also, the project is built on top of <a href="https://spring.io/projects/spring-boot">Spring Boot</a> with Lombok library which I haven’t been using for a very long time. And this story is about Lombok, at least part of it :)</p><h2>Background</h2><p>As you might know, Lombok is used to simplify Java development, to avoid playing with most of the boilepart in Java like getters/setters, constructors, builders, and so on.</p><p>On the first glance, it looks like a silver bullet to all the problems that have been reported by the Java community for years. With a single annotation, you can save a lot of time instead of manually writing all these setters/getters, implementing proper constructors or <a href="https://stackoverflow.com/search?q=%5Bjava%5D%2BhashCode%2Bequals&amp;s=4f9d81bb-6238-49bb-8d4c-2c223c56213b">digging StackOverflow</a> how to implement <code>hashCode</code> and <code>equals</code> in the right way.</p><p>Here is a simple example how Lombok saves your time (this is a real example from the project I’m working right now):</p><pre><code>@Data @Builder @Jacksonized @JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class) public class Job { public enum Type { DELIVERY, PICKUP; @JsonValue @Override public String toString() { return super.toString().toLowerCase(); private long id; private Type type; }</code></pre><p>With just a few annotations on top of the class, you get a full-blown class with JSON support. You can also use a <em>builder</em> to construct instances of the class in a clean and efficient way. Let’s see how this class is used:</p><pre><code>return stop.getOrders().stream() .map(order -&gt; Job.builder() .id(order.getId()) .type( order.getDeliveryLocation().equals(stop.getLocation()) ? Job.Type.DELIVERY : Job.Type.PICKUP) .build()) .collect(Collectors.toList());</code></pre><p>So you can use the builder to simply create a new instance, you can use fluent API to have easy to read code. </p><p>At first glance, everything seems right, doesn’t it?</p><h2>Wrong!</h2><p>I’ll just focus on the one aspect here — the <code>Builder</code> annotation. It gives me the <code>.builder()</code> method that returns an instance of the <code>Builder</code> class with dedicated methods to set proper values for each field defined in the <code>Job</code> class.</p><p>Yet, if you take a closer look, you will notice a line with <code>enum</code> Type definition. This enum tells me what kind of <code>Job</code> objects I can create — either <code>PICKUP</code> or <code>DELIVERY</code>. Yet the <code>Builder</code> doesn’t pursuit so, check the code below:</p><pre><code>Job.builder().id(1L).build()</code></pre><p>Does this create a proper instance? What type of job did I create? Is the <code>Job</code> instance valid?</p><p>As you can see, all the questions are valid and you cannot acknowledge them. What the above code built is totally invalid object — from the business point of view to be clear, but we do implement a business logic and not just code that should look nice.</p><p>Sure, you can complain that this is a developer’s fault, they should know what they are doing, they should know all those inner dependencies between <code>id</code> and <code>type</code> — this isn’t API responsibility to be clear and helpful … right ;-)</p><p>Also, using the <code>Builder</code> annotation this way, you do nothing than this:</p><pre><code>var job = new Job(); job.setId(1L); job.setType(PICKUP); return job;</code></pre><p>Just because you hide this, it doesn’t mean you create a good quality code.</p><h2>Thinking</h2><p>I think (therefore I am ;-) ) most of developers using Lombok these days stopped thinking about the domain they are modeling. They just throw a set of annotations into a class and go further, it sounds like they are paid by the line of code they are producing.</p><p>Lombok isn’t a hammer to nail all the problems, it’s a tool as any other and it’s our (developers') responsibility to use it properly.</p><p><strong>How can I improve this code?</strong> The answer is easy: take a look on it from business perspective, what does the domain expect to look like?</p><p>If you take look from such an angle, you’ll notice that you can create two kind of jobs: either a <code>pickup</code> job or a <code>delivery</code> job. There is no option to create any other kind of job right now (this can change in the future, but that’s another story to tell).</p><p>Having this in mind the only changeable thing is the <code>id</code> which uniquely identifies a job object. So we can model the class with two static constructors to only allow create two kind of jobs:</p><pre><code>@Data @AllArgsConstructor(access = AccessLevel.PRIVATE) @Jacksonized @JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class) public class Job { public enum Type { DELIVERY, PICKUP; @JsonValue @Override public String toString() { return super.toString().toLowerCase(); public static Job pickup(long id) { return new Job(id, Type.PICKUP); public static Job delivery(long id) { return new Job(id, Type.DELIVERY); private long id; private Type type; }</code></pre><p>Just by adding two <a href="https://en.wikipedia.org/wiki/Factory_method_pattern">factory methods</a> (yep, there is such a design pattern) — <code>pickup()</code> and <code>delivery()</code> — and by making constructor private I limited how this class can be constructed. This also simplifies the usage of the class:</p><pre><code>return stop.getOrders().stream() .map(order -&gt; order.getDeliveryLocation().equals(stop.getLocation()) ? Job.delivery(order.getId()) : Job.pickup(order.getId()) .collect(Collectors.toList());</code></pre><p>With the new approach, I was able clearly expose what kind of objects a user of my API can create, what is needed to create those objects and just left two entry points into the API. User of the API doesn’t need to know if there is any dependency between <code>id</code> and <code>type</code>.</p><p>Another thing that shows up is the <code>enum</code> — it doesn’t have to to be exposed at all, it’s an internal <code>Job</code>‘s thing that should be hidden. How to do it?</p><pre><code>@Data @AllArgsConstructor(access = AccessLevel.PRIVATE) @Jacksonized @JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class) public class Job { private enum Type { DELIVERY, PICKUP; @JsonValue @Override public String toString() { return super.toString().toLowerCase(); public static Job pickup(long id) { return new Job(id, Type.PICKUP); public static Job delivery(long id) { return new Job(id, Type.DELIVERY); private long id; private Type type; public boolean isPickup() { return Type.PICKUP.equals(this.type); public boolean isDelivery() { return Type.DELIVERY.equals(this.type);