![]() ![]() By modifying the compiler’s AST, Lombok is indirectly altering the final bytecode generation itself. Lombok does not really fall into these categories: What it does is modify the compiler data structures used to represent the code i.e., its abstract syntax tree (AST). Maybe the most common case for annotation processors is to generate new source files or perform some kind of compile-time checks. Then, as the compile process is going on, whenever the compiler finds an annotation it sort of asks: “Hey, anybody in the classpath interested in this For those processors raising their hands, the compiler then transfers control to them along with compile context for them to, well… process. The idea is that users can put annotation processors (written by oneself, or via third-party dependencies, like Lombok) into the build classpath. Annotation processing is a feature added to the Java compiler at version 5. Lombok acts as an annotation processor that “adds” code to your classes at compile time. Let’s see how Lombok does its magic and some usage examples. Lombok’s creators are a couple of very smart guys, and certainly have a taste for humor-you cannot miss this intro they made at a past conference! It enables us to drastically reduce the amount of “boilerplate” code we need to write. Add some constructs and class patterns we Java developers often need to use and we frequently end up with many lines of code that bring little or no real value other than complying with some set of constraints or framework conventions. However, as a programming language, Java has some idiosyncrasies of its own as well as design choices that can make it rather verbose. Java is mature and performant, and the community and ecosystem around it are huge and lively. To do this you need to call the delombok command provided in the lombok.Java has many things going for it beyond just the JVM itself, which is a remarkable piece of software. Fortunately Lombok easily allows us to revert all “lomboked” classes to vanilla Java using a process called delombok. Not every dependency added to the project stays there forever and sometimes we need to get rid of one to move forward. The compiler then uses this modified AST to generate bytecode for Lombok-generated methods and fields as if they were written by a developer. By using a non-public API, they managed to modify ASTs provided by the compiler to add new methods, fields, and even classes during the compilation phase. The standard’s original intention is that libraries would only inspect ASTs, particularly annotations, and use them to implement custom code validations or generation of new source files.īut Lombok creators figured out that they can use this feature differently. On it, the compiler performs various checks and transformations and then uses the resulting AST to generate the final bytecode instructions.īased in this, Java 6 has introduced the Pluggable Annotation Processing API (standardized by JSR 269), which allows Java libraries to execute custom code during compilation. An AST contains all information about the original code such as classes, methods, and program statements. During compilation, it does some heavy lifting and converts the source code into a tree structure called abstract syntax tree (AST). If annotations are used on the class level Lombok will generate getters and setters for all fields in the class.īut before we come to that we have to understand the Java compiler a little better. To make this case even more concise, Lombok allows using these annotations on the class level. What about these repetitive annotations? It’s handy to use them like this if you need to expose only a couple of fields in your class, but if you need to generate accessors for all your fields, it becomes annoying. I would argue this code is already much better than what we’ve started with, but it still does not look concise. It has elements that are common to POJO classes: getters, setters, equals, hashCode, and toString method. Take a look at this regular POJO class with just three fields: name, surname, and age. In this post, I’ll show you how to rewrite POJOs in only a few lines of code with Lombok. The situation got better with the introduction of lambdas and streams in Java 8, but it is still sub-par in some areas, like writing plain old Java objects POJO. On the other hand, it’s very verbose and requires writing massive amounts of boilerplate code for common tasks. On one hand, it’s a mature programming language with a diverse number of frameworks and libraries that make development relatively easy. I have a love/hate relationship with Java. ![]()
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