This leads to dysfunctional and unportable code, and breaks the object oriented principle of abstraction and containment. For example - We can access the private members of a class which is illegal with non-reflective operations. Reflection needs a runtime permission which may not be available when running under a security manager, such as in an Applet.Įxposure of Internals: Java reflection enables us to perform certain operations which are illegal in non-reflective operations. The following issues affect both offline baking and. Security Restrictions: There are certain security impacts to using Reflection. Below are some tips for keeping the performance impact of reflection probes to a minimum. In performance sensitive applications, reflective operations must be avoided in loops and frequently called sections of code. Any use outside of that should be heavily scrutinized. Explaining the Java Reflection API and providing techniques for using it effectively, this guide describes the capabilities that allow a program to examine. When an operation can be performed non-reflective as well as reflective operation, always prefer the non-reflective operation. Reflection was created for a specific purpose, to discover the functionality of a class that was unknown at compile time, similar to what the dlopen and dlsym functions do in C. with this flexibility comes its disadvantage - certain java virtual machine optimizations cannot be performed when types are resolved dynamically leading to slower performance as compared to normal class and method operations. Performance overhead: Reflection works by dynamically resolving and inspecting classes and its members. For example, if you want to map a lot of schema-types to a single Java type based on a reliable naming convention and consistent structure, SAX could be a great choice for that.What are the disadvantages of Reflection? And even if you do want to, there's nothing that requires you to make your structures one-to-one with the XML schema. There's no requirement that you map XML structures to types. Stax - A balance between usability and efficiency.A little awkward for a lot of Java developers SAX - Very fast and low memory requirements.Heavy memory footprint and a little sluggish If you want to work with XML using dynamic approaches, there are a number ways to accomplish that in Java. Assuming there's no other reason you need these class definitions, it's not clear why you would want to generate classes in the first place. But how else are you going to let your foot shoot it self in the foot?īasically what it comes down to here is that you are asking is it's a good idea to generate a ton of statically defined classes and then use reflection to avoid referencing them in a static way. Using Reflections you can query for example: Subtypes of a type Types annotated with an annotation Methods with annotation, parameters, return type Resources found in classpath And more. Of course the real problem of using reflection here is it gives you the power to consume a WSDL so poorly designed that you need these kinds of shenanigans to consume it. Java runtime metadata analysis Reflections scans and indexes your project's classpath metadata, allowing reverse transitive query of the type system on runtime. Get a profiler to tell you where your real problems are. Don't let fear keep you from trying ideas. Make it obvious where the problem is.Īs for performance, there are real issues but mostly I've been surprised how fast aspect oriented solutions are. If someone suspects reflection is causing an object to behave oddly, don't make their effort to find the cause an epic journey through the code base. Create an isolated space to use it where it's walled off from the rest of your code, and forbid its use where you don't have a real good need for it. Following such rules makes reasoning about the code easier. You must weigh all that against the benefit you're going to get by using reflection to help you consume this WSDL. Consequently, reflective operations have slower performance than their non-reflective counterparts, and should be avoided in sections of code which are called frequently in performance-sensitive applications. Once reflection is on the table you have to read all the code in the code base to know how immutable it is. Because reflection involves types that are dynamically resolved, certain Java virtual machine optimizations can not be performed. When you know there is no reflection used in the code base you can look at only the class to know that it is immutable. This makes reasoning about how the code behaves difficult. Reflection is a powerful tool that should be used wisely.įor example, a class that has been carefully designed to create immutable objects can be quietly defeated with reflection. These perfectly valid concerns are used by some shops as excuses to swear off ever using reflection. Reflection can cause performance problems.Reflection can break protections like private.There are two fundamental things about reflection that can make it bad.
0 Comments
Leave a Reply. |