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I love Java, but there are few things that I hate about it. One of them is it’s verbosity. You have to write a lot of code to achieve what you could achieve with almost half or fewer lines of code in other functional/scripting languages.
There are many justifications for it’s verbosity -
ダウンロードしたlombok.jarとMVNRepositoryで指定したバージョンは合わせた方が良いと思われる。 eclipse再起動! インストーラの操作をするとインストーラで指定したeclipseのディレクトリ階層にlombok.jarが配置される。 同じ階層にeclipse.iniというファイルがあり. I did install Lombok in Spring Tool Suite 4 just some days ago for Mac and Windows. And none problems. Execute java -jar lombok.jar. Note: normally or by default, it does not find the installer, it is the common scenario in my experience.; Two. Press the Specify Location button. Note: for Mac, go to the Contents directory within the.app file and find the STS.ini file, it could be. Start Lombok Installation - Once the jar downloaded in Local repository, goto the jar location from command prompt and run the following command java -jar lombok-1.16.18.jar and we should be greeted by Lombok installation window provided by lombok like this.
- Java’s verbosity makes it more expressive and understandable.
- It improves readability of code.
- It makes Java programs easier to debug.
- Insert more justifications here…
While all of the above justifications are true, the amount of boilerplate code required to be written to do even minimal jobs can be very annoying.
Consider the following example of a Plain Old Java Object (POJO) -
This is a small class with only five fields, but we had to write almost 50 lines of code for something so simple. Most of the code in the above class was required to write getters and setters. Now, imagine hundreds of similar data classes in your project and imagine the number of lines of code that has to be written just to provide getters and setters.
Getters
, Setters
, toString
, hashCode
methods are something which are alike in almost all your data classes, So there must be a better way to handle these common constructs right?Enter Project Lombok! It is an honest attempt to reduce Java’s boilerplate code using simple set of annotations.
How Project Lombok helps in reducing boilerplate code?
Project lombok works like magic from the outside. It provides you with a series of annotations that you can use in your classes. It, then generates and injects code into your classes at compile time by processing these annotations.
Let’s make the above User class boilerplate-free by using Lombok’s annotations -
The annotations
@Getter
and @Setter
will automatically generate the default getters and setters for all the fields in your class. Awesome! isn’t it?Well! At this point, you might say that what’s the need for all this when any good IDE can generate getters and setters for you?
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Yeah! But, think about it, the code for getters and setters will still lie around your class files and you will have to manage this code. Also, whenever you change or add a new property, you will need to modify existing getters/setters or add new ones.
But, with lombok, you won’t need to do any of it. You can just write your data classes and forget about other boilerplates.
Installation and Usage
Lombok is available as a single jar file on the Project’s website. Download
lombok.jar
and follow the instructions here to install and use it in your development environment -Usage with javac
Lombok works out of the box with
javac
. Just add it in the classpath while compiling your program and you’re ready to go!Installing and using Lombok in eclipse
lombok.jar
comes with an installer. Just double click the jar, the installer will open which will automatically detect all the supported IDE’s in your machine -I have eclipse installed in my machine and the installer has detected it. Click
Install/Update
to install lombok.jar in eclipse.Note however that
lombok.jar
will still need to be added in the classpath of any projects that will use lombok annotations. If you’re using maven, you can simply add the following dependencies in the pom.xml file to include lombok -For gradle, add the following to your build.gradle file
If you don’t use any build system in your project, do the following to add lombok in classpath -
Installation in IntelliJ Idea
Lombok doesn’t have direct support for intellij idea. But there is a plugin that adds support for most features. To install lombok plugin in intellij -
That’s it. Now you can use lombok in your project. Don’t forget to add lombok dependencies as described above in your
pom.xml
or build.gradle
file.Lombok Annotations
In this section I’ll discuss about different annotations provided by lombok for reducing boilerplate code. You can choose to use the annotations that fits your need -
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1. @Getter and @Setter
Lombok’s
@Getter
and @Setter
annotations are used to generate the default getter and setter methods for the instance variables of a class.These annotations can be applied at field level, or at class level. If you apply the annotations at class level, getters and setters will be generated for all the non-static fields of your class.
Let’s see an example -
The above lombok annotated code is equivalent to the following Java code -
The generated getter and setter methods will be public by default, but, you can modify this behaviour by specifying an
AccessLevel (PRIVATE, PROTECTED, PACKAGE, PUBLIC, or NONE)
with the annotation -Getter/Setter generation for any field can be disabled manually by using the special
AccessLevel.NONE
access level. This lets you override the behaviour of @Getter
, @Setter
annotation on a class -Getters and Setters will not be generated if there is already a method with the same name and parameters in your class.
2. @NonNull
@NonNull
annotation is used to generate null-checks for the annotated fields. If it is used on an instance variable, all the setter methods, or constructors generated by lombok will contain a null-check for that instance variable.If the
@NonNull
annotation is used on the parameter of a method or constructor, a null-check for that parameter will be inserted inside the method or constructor.The null-check looks like -
if(param null) throw new NullPointerException('param');
. It is inserted at the very beginning of your method. For constructors, it is inserted immediately after any this() or supper() calls.Note that, if a null check is already present at the top of a method or constructor, it will not be generated by lombok. Let’s consider a simple example -
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The above annotated code is equivalent to the following java code -
3. @ToString
Add
@ToString
annotation to your classes to generate an implementation of toString()
method. The default implementation will print your class name along with the value of each fields separated by commas -Following is the equivalent Java Code -
If you want to include field names as well in the toString() method, use
@ToString(includeFieldNames=true)
.By default, all the non-static fields of the class will be printed. If you want to exclude some fields from toString(), use
@ToString(exclude='fieldName')
. Moreover, you can specify exactly which fields to include in toString() using - @ToString(of={'field1', 'field2'})
Also, you can use
@ToString(callSuper=true)
to include the output of the superclass implementation of toString() to the output.4. @EqualsAndHashCode
You can annotate a class with
@EqualsAndHashCode
to generate implementations of equals()
and hashCode()
methods. By default, it will use non-static and non-transient fields, but you can exclude more fields using exclude
parameter, or, you can include selected fields using of
parameter.Also, like
@ToString
, you can use callSuper=true
with @EqualsAndHashCode
as well. This will cause lombok to call the equals/hashCode method of super class before considering fields in the current class.And following is the equivalent Java code -
5. @NoArgsConstructor, @RequiredArgsConstructor and @AllArgsConstructor
@NoArgsConstructor
will generate a constructor with no parameters. If this is not possible, typically, because of final variables which must be initialized, compiler will generate an error. If @NoArgsConstructor(force=true)
is used then all the final variables will be initialized with 0/false/null.Download Lombok Jar For Mac Osx
The above lombok annotated code, after processing looks like -
@RequiredArgsConstructor
generates a constructor with all un-initialized final fields and @NonNull fields. An explicit null check is also generated for fields marked with @NonNull
-For the above class, fields
id
, name
and department
are not included in the generated @RequiredArgsConstructor
because id
and name
are already initialized and department
is neither final nor annotated with @NonNull
. -@AllArgsConstructor
generates a constructor with all the fields in your class. Also, null-checks are added for fields marked with @NonNull
.Project Lombok Jar
6. @Data
@Data
annotation is the combination of @Getter
, @Setter
, @ToString
, @EqualsAndHashCode
and @RequiredArgsConstructor
annotations. It lets you generate all the boilerplate code that is normally associated with a Plain Old Java Object (POJO) with just a single annotation.Conclusion
Lombok Jar Maven
We explored the most commonly used annotations provided by lombok. However, there are a lot of other useful annotations available in the library. Some of my favourites are -
Download Lombok
I urge you to have a look at the Lombok’s Feature Page to explore these annotations as well. Thank you for reading my blog. Please ask any doubts or clarifications in the comment section below.