The article was initially published at carloschac.in
See also:
๐ฉ Immutability in Java ๐ฅ Made Easy
Carlos Chacin โ๐ฝ ใป Apr 12 '20
In this article, we are going to compare some of the features of the Immutables.org library, Google AutoValue and Project Lombok:
- Generated the
Builder
pattern by default? - Generated helper methods for, i.e.,
Optional
andList
? - The number of lines of code to write?
- Required IDE's plugins?
- Are the objects immutable?
The three libraries are based on an annotation processor to generate/modify code for us:
- Immutable classes
-
equals
,hashCode
andtoString
methods - other utilities
NOTE: Immutables
and AutoValue
generate new classes with the processor, and Lombok
modifies the bytecode of the original class.
๐ก Overview
Immutables Java annotation processors to generate simple, safe, and consistent value objects. Do not repeat yourself, try Immutables, the most comprehensive tool in this field!
AutoValue provides an easier way to create immutable value classes, with a lot less code and less room for error, while not restricting your freedom to code almost any aspect of your class exactly the way you want it.
Project Lombok is a java library that automatically plugs into your editor and build tools, spicing up your java.
Never write another getter or equals method again, with one annotation your class has a fully-featured builder, Automate your logging variables, and much more.
๐ The Model
We are going to create a class using the three libraries to be able to create an object representation with the following fields.
Optional<Integer> myOptional;
String myString;
List<String> myList;
๐ฉ Creating the model with AutoValue
package autovalue;
import com.google.auto.value.AutoValue;
import java.util.List;
import java.util.Optional;
@AutoValue
public abstract class MyModel {
public abstract Optional<Integer> myOptional();
public abstract String myString();
public abstract List<String> myList();
// Builder not generated by default
// We have to write this boilerplate code
@AutoValue.Builder
public abstract static class Builder {
public abstract Builder setMyOptional(Optional<Integer> myOptional);
public abstract Builder setMyString(String myString);
public abstract Builder setMyList(List<String> myList);
public abstract MyModel build();
}
}
- Generated the
Builder
pattern by default? ๐ด - Generated helper methods for, i.e.,
Optional
andList
? ๐ด Let's see in the next section - The number of lines of code to write? 28 โ
- It requires IDE plugin ๐ด
- Are the objects immutable? ๐ด Let's see in the next section
๐ฉ Creating the model with Lombok
package lombok;
import java.util.List;
import java.util.Optional;
@Value
@Builder
public class MyModel {
Optional<Integer> myOptional;
String myString;
List<String> myList;
}
- Generated the
Builder
pattern by default? ๐ด - Generated helper methods for, i.e.,
Optional
andList
? ๐ด Let's see in the next section - The number of lines of code to write? 14 โ
- It requires IDE plugins ๐ด
- Are the objects immutable? ๐ด Let's see in the next section
๐ฉ Creating the model with Immutables
package immutables;
import org.immutables.value.Value;
import java.util.List;
import java.util.Optional;
@Value.Immutable
public interface MyModel {
Optional<Integer> myOptional();
String myString();
List<String> myList();
}
- Generated the
Builder
pattern by default? โ - Generated helper methods for, i.e.,
Optional
andList
? โ , Let's see in the next section - The number of lines of code to write? 15 โ
- It doesn't require IDE plugin โ
- Are the objects immutable? โ , Let's see in the next section
๐ตTests
Let's check some Pseudo-code:
We are going to create two identical lists with the same element inside:
list1=List.of("OneValue")
list2=List.of("OneValue")
We are going to create two identical value objects like this:
MyModel1: (
myOptional=Optional.of(1)
myString="Hello"
myList=list1 // Using list 1
)
MyModel2: (
myOptional=Optional.of(1)
myString="Hello"
myList=list2 // Using list 2
)
Even when using different references for the lists, the objects should be equal by value.
model1 == model2 // TRUE
After mutating one of the lists, the comparison of the objects should be the same
list1.add("AnotherValue")
model1 == model2 // TRUE
๐ญ Testing AutoValue
@Test
void immutability() {
// Create 2 lists containing the same element
var myList1 = new ArrayList<String>();
myList1.add("OneValue");
var myList2 = List.of("OneValue");
// Create model 1, assigning the list1
var myModel1 = new AutoValue_MyModel.Builder()
.setMyOptional(Optional.of(1)) // ๐ฅ ๐ด No helper for Optional
.setMyString("Hello")
.setMyList(myList1) // ๐ฅ ๐ด No helper for List
.build();
// Create model 2, assigning the list2
var myModel2 = new AutoValue_MyModel.Builder() // ๐ฅ ๐ด No helper for copying
.setMyOptional(Optional.of(1))
.setMyString("Hello")
.setMyList(myList2)
.build();
// Compare the 2 objects
// Test passes since the fields contain the same values
assertThat(myModel1).isEqualTo(myModel2);
// Mutate the list used on Model 1
myList1.add("AnotherValue");
// Compare the 2 objects:
// - PASSES objects are NOT equal for AutoValue ๐ฎ ๐ด
assertThat(myModel1).isNotEqualTo(myModel2);
}
๐ญ Testing Lombok
@Test
void immutability() {
// Create a mutable list with 1 element
var myList1 = new ArrayList<String>();
myList1.add("OneValue");
var myList2 = List.of("OneValue");
// Create model 1, assigning the list1
var myModel1 = MyModel.builder()
.myOptional(Optional.of(1)) // ๐ฅ ๐ด No helper for Optional
.myString("Hello")
.myList(myList1) // ๐ฅ ๐ด No helper for List
.build();
// Create model 2, assigning the list2
var myModel2 = MyModel.builder() ๐ฅ ๐ด // No helper for copying
.myOptional(Optional.of(1))
.myString("Hello")
.myList(myList2)
.build();
// Compare the 2 objects
// Test passes since the fields contain the same values
assertThat(myModel1).isEqualTo(myModel2);
// Mutate the list used on Model 1
myList1.add("AnotherValue");
// Compare the 2 objects:
// - PASSES objects are NOT equal for Lombok ๐ฎ ๐ด
assertThat(myModel1).isNotEqualTo(myModel2);
}
๐ญ Testing Immutables
@Test
void immutability() {
// Create a mutable list with 1 element
var myList1 = new ArrayList<String>();
myList1.add("OneValue");
var myList2 = List.of("OneValue");
// Create model 1, assigning the list1
var myModel1 = ImmutableMyModel.builder()
.myOptional(1) // ๐ฉ โ
Helper for Optional
.myString("Hello")
.myList(myList1)
.build();
// Create model 2, assigning the list2
var myModel2 = ImmutableMyModel.builder()
.from(myModel1) // ๐ฉ โ
Helper for copying
.addMyList("OneValue") // ๐ฉ โ
Helper for List
.build();
// Compare the 2 objects
// Test passes since the fields contain the same values
assertThat(myModel1).isEqualTo(myModel2);
// Mutate the list used on Model 1
myList1.add("AnotherValue");
// Compare the 2 objects:
// - Test PASSES objects ARE EQUAL for Immutables ๐ฉ โ
assertThat(myModel1).isEqualTo(myModel2);
}
๐ Results
AutoValue | Lombok | Immutables | |
---|---|---|---|
Line of Code to write/maintain | 28 | 14 | 15 |
Builder (by default) | ๐ด | ๐ด | โ |
Required IDE Plugin | โ | ๐ด | โ |
Immutability | ๐ด | ๐ด | โ |
Helper for Optional | ๐ด | ๐ด | โ |
Helper for Collections | ๐ด | ๐ด | โ |
Helper for Copying | ๐ด | ๐ด | โ |
The code and the tests for the above examples are available on GitHub:
cchacin / immutables-autovalue-lombok
โ๏ธ Immutables/AutoValue/Lombok ๐ฅ Which One?
โ๏ธ Immutables/AutoValue/Lombok ๐ฅ Which One?
Blog post: https://dev.to/cchacin/immutables-autovalue-lombok-which-one-2j33
๐ Conclusions
Even when the three libraries are doing a great job to avoid the boilerplate code, I personally use the
Immutables
library in most of the projects because of the safe defaults.To be fair, both
Lombok
andAutoValue
can achieve also immutability but it requires paying more attention when creating the classes and that can cause problems.One main advantage of
AutoValue
is that it generates less code and that would be convenient if you are developing on/forAndroid
.The configuration options for
AutoValue
andLombok
are pretty limited compared withImmutables
but that topic was not covered in this article.Lombok requires a plugin if you want to be able to see all the modified/added methods to the bytecode.
Top comments (11)
You might want to check the vavr functional library. It has monads like Scala and it doesn't use annotations.
Hey Carlos,
From the final table I feel that your method to compare these libraries were: get all features that I care in Immutables and compare with the others.
It is your space and you have the right, but I don't think that is fair to the readers.
I'm more familiar with Lombok and there are some goods parts that are absent here. For instance?
If I don't want a builder? If my class has 3 attributes I don't really need a builder. How do I do that with the others? Will still be the same amount of boiler plate?
About "helper for copying": an builder in Lombok creates a toBuilder method that allows you to make a builder with all values, change the ones you want and rebuild the object.
Having an abstract class/interface defining your model, how these play together with jackson or hibernate where you have to annotate your class, how does it work?
What about if my fields are made of mutable fields, will Immutable still be immutable by default?
I don't even know the answer for all these questions but I think a fairer comparison would try to go beyond the set of features that your favorite library offers.
Hi Canem,
Thank you for reading the post and adding your comments and feedback.
As mentioned in the post, this is a comparison of some of the three libraries' features, not an extensive review of every single feature.
The particular set of evaluated features is based on the features that I consider essential for my use cases and are also defined at the beginning of the post.
Answering your question below:
Immutables is even more flexible than Lombok in that case, allowing you to choose between a simple constructor with the parameters, but also a static factory method
Good catch, Even when I do not evaluate that in the comparison, I'll remove the java comment in the lombok example.
For Hibernate/JPA, I do not use these libraries, IIRC the JPA standard requires JavaBeans mutable objects. But I do use them in particular for De/Serialization with Jackson, Jsonb, Gson, etc. and those play well with Interfaces and abstract classes.
Yes, and that is one of the critical aspects of the library, AutoValue and Lombok generate shallowly immutable classes.
There are a lot of additional features in the Immutables library that I consider useful. Lombok and AutoValue are not providing those, but I agree with the fact that it depends on the need and uses cases.
The three libraries work pretty well, and if you don't need any additional features from the immutables library, AutoValue and Lombok are also valid options.
I just checked the Lombok generated code and I cannot see the utility method for copying/cloning:
Can you point me to an example or documentation around that?
Its some time now, but maybe it still helps. The copy-function of lombok is @With, which creates a copy with one property changed.
For your example it might be something like
myModel1.withMyString("other string")
which will create a copy of
myModel1
with the changedmyString
value.Thats what I also like about lombok, that you can use just the parts you need. Immutable is hard to use for legacy code, since you need to adapt all at once, while lombok leaves you with the chance to enhance classes with just the stuff you need. Copy a class? Add
@With
to it. Want a builder? Add@Builder
to a class. Get rid of existing getters and setters? Just add@Getter
and/or@Setter
to it and delete whats already there.With lombok you could still generate code for JPA entities, since you can chose what you want to use, e.g. getters, setters, constructors, etc. Of cause there are pitfalls to watch out for, but it is usable, since it doesn't turn it immutable automatically.
In Testing Immutables you're not comparing a mutated myList1 vs myList2 like you did in the previous tests.
Hi am312, good catch, that variable is not actually used in the Immutables example, I'll update the example to remove that. Thanks
in order to do an apples-to-apples comparison, shouldn't you be using it? I guess you're trying to demonstrate if the libraries are doing a deep comparison of the collections' contained objects or just testing for ==.
I'm curious why you expect two objects which contain different lists to be equal? That is certainly not intuitive. Does Immutables allow for configuring deep equals comparisons?
Hey Carlos,
Why you don't test JAVA 14 record feature ?