![]() Iterate all fields: FieldAccess access = FieldAccess.get(SomeClass.class) įor(int i = 0, n = access. To make argument passing work, reflection APIs take a parameter that is an array of object s, one per argument. Int addNameIndex = access.getIndex("addName") Īccess.invoke(someObject, addNameIndex, "Awesome McLovin") SomeClass someObject = access.newInstance() įor maximum performance when methods or fields are accessed repeatedly, the method or field index should be used instead of the name: SomeClass someObject =. String name = (String)access.get(someObject, "name") Ĭonstructor reflection with ReflectASM: ConstructorAccess access = ConstructorAccess.get(SomeClass.class) įieldAccess access = FieldAccess.get(SomeClass.class) Īt(someObject, "name", "Awesome McLovin") String name = (String)access.invoke(someObject, "getName") įield reflection with ReflectASM: SomeClass someObject =. MethodAccess access = MethodAccess.get(SomeClass.class) Īccess.invoke(someObject, "setName", "Awesome McLovin") Method reflection with ReflectASM: SomeClass someObject =. To use reflectasm with maven, please use the following snippet in your pom.xml The above charts were generated on Oracle's Java 7u3, server VM. The source code for these benchmarks is included in the project. It can also access primitive fields via bytecode to avoid boxing. The access class uses bytecode rather than Java's reflection, so it is much faster. An access class is generated to set/get fields, call methods, or create a new instance. Young 218k 45 384 433 1 Wow I never knew that. ![]() Share Improve this answer Follow answered at 22:59 C. ReflectASM is a very small Java library that provides high performance reflection by using code generation. The first 15 runs (by default) of your reflected method is called using JNI after that, bytecode is generated and calling that reflected method would perform identically to calling that method directly in Java code. ![]() import use the ReflectASM discussion group for support. It takes any object as a parameter and uses the Java reflection API to print out every field name and value. One of my favorite uses of reflection is the below Java dump method. Most other modern languages use reflection as well, and in scripting languages (such as Python) they are even more tightly integrated, since it feels more natural within the general programming model of those languages. Lots of modern frameworks use reflection extensively for this very reason. The code can be written against known interfaces, but the actual classes to be used can be instantiated using reflection from configuration files. Reflection is important since it lets you write programs that do not have to "know" everything at compile time, making them more dynamic, since they can be tied together at runtime. More advanced uses lets you list and call methods, constructors, etc. if you declared it as an Object) - this might seem trivial, but such reflection is not possible in less dynamic languages such as C++. at runtime.įor example, all objects in Java have the method getClass(), which lets you determine the object's class even if you don't know it at compile time (e.g. Reflection is a language's ability to inspect and dynamically call classes, methods, attributes, etc. Support introspection, but do not support reflection. The distinction is necessary here as some languages Reflection is then theĪbility to make modifications at runtime by making use of Not reflection, but rather Type Introspection. The ability to inspect the code in the system and see object types is In dynamically typed languages, the use case described above is less necessary (since the compiler will allow any method to be called on any object, failing at runtime if it does not exist), but the second case of looking for methods which are marked or work in a certain way is still common. There are some good reflection examples to get you started at Īnd finally, yes, the concepts are pretty much similar in other statically typed languages which support reflection (like C#). JUnit 4, for example, will use reflection to look through your classes for methods tagged with the annotation, and will then call them when running the unit test. One very common use case in Java is the usage with annotations. Reflection in Java is one of the advance topic of core java. So, to give you a code example of this in Java (imagine the object in question is foo) : Method method = foo.getClass().getMethod("doSomething", null) Java's static typing system isn't really designed to support this unless the object conforms to a known interface, but using reflection, your code can look at the object and find out if it has a method called 'doSomething' and then call it if you want to. The name reflection is used to describe code which is able to inspect other code in the same system (or itself).įor example, say you have an object of an unknown type in Java, and you would like to call a 'doSomething' method on it if one exists.
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