How Expedia Is Getting Rid of Java Bean Transformers

The consequence of this is that there is no available mapping framework able to transform your objects in a simple way.

The solutionA library that can automatically transform all kinds of Java Beans, including Immutable, mutable and mixed would save us a lot of work and BULL does.

BULL logoThe benefitsTo better show the benefits of having this library in place, let’s go through an example: imagine that you are working on a multi-tier application, built as follow:Application architecture using classic transformersThe FooController contains a Rest API that gets a request in input and returns a response after having performed a set of operations.

To obtain the response, the FooController needs to get the request/response data (mapped by Domain objects similar to this) moving across the three layers so we do need to implement, for each one of them: a Transformer (plus its test), that copies, and modifies if needed, the data from one object to the other in the next layer.

Summarising, for each layer, we will need 20 classes divided up as follows:1 Service class1 Service class’s test6 Domain objects6 Transformers6 Transformer’s testsMultiplied for the 3 layers gives a total of 60 classes.

Let’s now analyze the same scenario using BULL:Application architecture using BULLNow the situation looks quite different: the Transformer classes are not needed anymore and the total classes we need for all 3 layers are reduced to just 24, and overall we have 60% less code.

That implies:That implies:Less development time (so direct cost reduction)Reduced possibility of introducing errorsCode that is easier to maintainWhat BULL can doBULL has been built trying to make its usage as much easy as possible, indeed to transform an object it’s needed just one line of code:ToBean toBean = new BeanUtils().

transform(fromBean, ToBean.

class);Supported featurescopy of immutable beans.

copy of mutable beans.

copy of hybrid beans (some fields private and some not).

copy of Java beans without getter and setters.

Validation through annotationscopy with Java primitive typescopy with Java Collection typescopy with nested map fieldscopy with Array containing primitive and not object typescopy with property name mappingcopy with recursion copylambda function field transformationThe full list of features, always updated including examples, is available here.

Transformation in real lifeWe know that, in real life, it’s rare that we just need to copy information between two Java Beans almost identical, often occurs that:the destination object has a totally different structure than the source objectwe need to perform some operation on a specific field value before copying itthe destination object’s fields have to be validatedthe destination object has an additional field than the source object that needs to be filled with something coming from a different sourceHow we can solve this?.well BULL gives you the possibility to perform any kind of operation on a specific field!Taking advantage of lambda expressions the developer can define its own method that will be applied to the a value before copying it.

Let’s explain it better with an example:Given the following Source class:public class FromFoo { private final String id; private final String val; private final List<FromSubFoo> nestedObjectList; // all args constructor // getters}and the following Destination class:public class MixedToFoo { public String id; @NotNull private final Double val; // constructors // getters and setters}and assuming that the val field needs to be multiplied by a random value in our transformer, we have 2 problems:The val field has a different type than the Source object, indeed one is String and one is DoubleWe need to instruct the library on how we would apply out math operationWell, this is pretty simple, you just need to define your own Lambda Expression that does that:FieldTransformer<String, Double> valTransformer = new FieldTransformer<>("val", n -> Double.

valueOf(n) * Math.

random());The expression will be applied to the field with the name: “val” in the destination object.

The last step is to pass the function the BULL instance:beanUtils.

getTransformer() .

withFieldTransformer(valTransformer) .

transform(fromFoo, MixedToFoo.

class);For what concerns the “field validation” aspect, it’s even simpler as you only need to annotate your field with one of the existing javax.


constraints (or defining a custom one) and that’s it.

How did we get there?As we used to implement tons of Java Bean Transformers that, too often, required more implementation time than the core feature we were working on, we decided to start implementing something that would speed-up our development process and that could be useful to all the ones who were dealing with the same issue.

Thanks to the Hotels.

com company culture, we had half-a-day per week to spend on Innovation projects.

Taking the opportunity for implementing this, and other products, are now showing their benefit.

In this particular case, we markedly reduced the development time of several of the features we work on.

Why Open SourcingOSS also has long-term viability.

It’s created and supported by a worldwide community of organizations and individual developers, many of whom also live by open source values like collaboration and volunteerism.

OSS is supported by a community of developers.

These same development shops are constantly reviewing the OSS code they support, as are thousands of independent developers working on the project worldwide.

The result is a vast peer review process that ensures security and accountability.

OSS has strong values — and more often than not, OSS shops and developers hold similar values — they are advocates for more community participation, collaboration, and volunteerism.

They believe in working together to build free, high-quality products that are accessible to for-profit and nonprofit organizations alike.

This belief underlines the mission of the best OSS shops and developers.

It pushes them to build new features and contribute these features back to the community.

As a direct result, popular OSS projects are often on the cutting-edge of technology.

Key TakeawaysDedicating some business hours to Innovation may encourage developers to express their potentiality, creating solutions that would be useful in daily activitiesMake Open Source, products or solutions that solve a common problem may help other peoplePassion is a key ingredient for good softwareBULL provides a useful speed-up of the development phase whilst it reduces the possibility of introducing errorsIn real-world scenarios, BULL does not introduce any performance degradationUseful linksThird Party Libraries comparisonUsage examplesHow to test the library into a real applicationPerformancesCode repositoryJavadocSiteGitter chatTutorial projectThis article has been originally published by InfoQ.

 However, We are currently working on creating a tutorial for using the library in a real project, it will be published soon on Dzone, updates will come.

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