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1. Java reflection invoke method how to#
2. Java reflection invoke method manual#
3. Java reflection invoke method code#

That is why the analysis does not accept Class arguments coming from static fields, since the contents of those can change at any time, even if the fields are final.Īlthough this may seem too restrictive, it covers the most commonly used patterns of the Reflection API calls. The analysis follows a simple rule: if all the writes to the array happen in linear sections of code, i.e., no control flow splits, then the array is effectively constant for the purpose of analyzing the call. Therefore, all the changes to the array between the time it is allocated and the time it is passed as an argument need to be tracked. This last restriction is due to the fact that Java does not have immutable arrays. The calls are intercepted and processed only when it can be unequivocally determined that the parameters can be reduced to a constant.įor example, the call Class.forName(String) will be replaced with a Class literal only if the String argument can be constant folded, assuming that the class is actually on the classpath.Īdditionally, a call to Class.getMethod(String, Class) will be processed only if the contents of the Class argument can be determined with certainty.

Java reflection invoke method code#

Second, GraalVM can employ constant folding and optimize the code further. If the target elements cannot be resolved, e.g., a class is not on the classpath or it does not declare a field/method/constructor, then the calls are replaced with a snippet that throws the appropriate exception at run time.įirst, at run time there are no calls to the Reflection API. If the target elements can be resolved, the calls are removed and instead the target elements are embedded in the code. If the arguments to these calls can be reduced to a constant, Native Image tries to resolve the target elements.

The analysis intercepts calls to Class.forName(String), Class.forName(String, ClassLoader), Class.getDeclaredField(String), Class.getField(String), Class.getDeclaredMethod(String, Class), Class.getMethod(String, Class), Class.getDeclaredConstructor(Class), and Class.getConstructor(Class). See also the guide on assisted configuration of Java resources and other dynamic features.

Java reflection invoke method manual#

Where the analysis fails, the program elements reflectively accessed at run time must be specified using a manual configuration. Native Image tries to resolve the target elements through a static analysis that detects calls to the Reflection API. (Note: loading classes with Class.forName(String) are included here since it is closely related to reflection.) Native Image has partial support for reflection and needs to know ahead-of-time the reflectively accessed program elements.Įxamining and accessing program elements through .* or loading classes with Class.forName(String) at run time requires preparing additional metadata for those program elements. We will get the metadata of below class named Guru99Base.Java reflection support (the .* API) enables Java code to examine its own classes, methods, fields and their properties at run time. Public Class getInterfaces() : Returns an array of interfaces implemented by the specified class.public Class getSuperclass(): Returns the super class reference.Public String getName (): Returns the name of the class.

Java reflection invoke method how to#

Example 1: How to get Metadata of Class.How to get complete information about a class.The package provides many classes to implement reflection java.Methods of the class is used to gather the complete metadata of a particular class. One advantage of reflection API in Java is, it can manipulate private members of the class too.

Reflection API in Java is used to manipulate class and its members which include fields, methods, constructor, etc. Java Reflection is the process of analyzing and modifying all the capabilities of a class at runtime.