![]() ![]() The second trade-off is that you must use a separate tool/plugin provided by the vendor to use the framework. ![]() And don’t forget that now you should debug generated code but not your code. Code generation changes your original code therefore, if something goes wrong, you cannot tell whether it is your mistake or a glitch in the code processing algorithms. It looks very promising, but are there any trade-offs here? And the answer is: yes.įirst off, you can run code that is not exactly yours. Those do not create and inject beans during startup using Class.newInstance(), do not use reflective method calls in listeners, etc. into your code, therefore making applications faster. By using annotation processing, type visitors, and other techniques, they add direct method calls, object instantiations, etc. And recent frameworks are trying to get rid of reflection completely by using ahead-of-time compilation and code generation. Those two metrics are vital in the age of microservices and serverless applications. Nowadays, we can see a rise of new frameworks like Micronaut and Quarkus that are targeted to two aims: fast start time and low memory footprint. The first candidate for reflection replacement is code generation. ![]() AOT Compilation and Code Generation: Make Applications Fast Again And I doubt that it will be changed in the near future mature frameworks are big and complex and used in many mission-critical systems, and because of this, developers should introduce big changes carefully. You need to dig really deep into all these invoke() and proxy() calls.īut if you look into event listener implementations in Spring or JPA callbacks in Hibernate, you will see familiar references inside. Traceability - if a reflective method call fails, it might be tricky to find a line of code that caused this because stack trace is usually huge. If you write a code that invokes a method via its reference and passes wrong parameters, the invocation will fail at runtime, not at compile time or load time. Type safety - if you use method reference in your code, it is just a method reference. We can see a great improvement in reflection API performance with every JVM release, JIT compiler’s optimization algorithms are getting better, but reflective method invocations are still about three times slower than direct ones. Speed - reflection calls are slower than direct calls. Some AOP frameworks rely on reflection for method execution interception.Īre there any problems with reflection? We can think of about three of them: Also, you can add aspect-oriented programming to this list. For the most popular IoC frameworks, the reflection API is a cornerstone because of extensive usage of class proxying, method reference usage, etc. Just think about annotation processing, data serialization, method binding via annotations, or configuration files. I’d dare to say that Java won’t become what it is now without reflection. "Reflection is the ability of a computer program to examine, introspect, and modify its own structure and behavior at runtime."įor most Java developers, reflection is not a new thing and it is used in many cases. In this article, we’ll look at reflection API, pros and cons for its usage, and review other options to replace reflection API calls - AOT compilation and code generation and LambdaMetafactory. Reflection calls have their cost, and if you develop a production-class framework, even tiny improvements may pay back in a short time. You can always implement method listener by storing instances for annotated methods and invoke them like it is implemented in many frameworks, but we decided to have a look at other options. In the previous version of the framework, a lot of boilerplate code registering listeners in screen’s init() method made your code almost unreadable, so the new concept should have cleaned this up. ![]() In the new version of the CUBA framework, we decided to improve many aspects of the architecture and one of the most significant changes was deprecating “classic“ event listeners in the controllers UI. In such cases, you always have an answer: use reflection! Sometimes, as a developer, you may bump into a situation when it’s not possible to instantiate an object using the new operator because its class name is stored somewhere in configuration XML or you need to invoke a method that's name is specified as an annotation property. ![]()
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