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 constructor 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 constructor 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. initargs) method.Java reflection support (the .* API) enables Java code to examine its own classes, methods, fields and their properties at run time. The following example shows the usage of .newInstance(Object.
InvocationTargetException − if the underlying constructor throws an exception.ĮxceptionInInitializerError − if the initialization provoked by this method fails. InstantiationException − if the class that declares the underlying constructor represents an abstract class. IllegalArgumentException − if the number of actual and formal parameters differ if an unwrapping conversion for primitive arguments fails or if, after possible unwrapping, a parameter value cannot be converted to the corresponding formal parameter type by a method invocation conversion if this constructor pertains to an enum type. IllegalAccessException − if this Constructor object is enforcing Java language access control and the underlying constructor is inaccessible. a float in a Float) ReturnsĪ new object created by calling the constructor this object represents. Initargs − array of objects to be passed as arguments to the constructor call values of primitive types are wrapped in a wrapper object of the appropriate type (e.g.
IllegalAccessException, IllegalArgumentException, InvocationTargetException Declarationįollowing is the declaration for .newInstance(Object. Individual parameters are automatically unwrapped to match primitive formal parameters, and both primitive and reference parameters are subject to method invocation conversions as necessary. initargs) method uses the constructor represented by this Constructor object to create and initialize a new instance of the constructor's declaring class, with the specified initialization parameters.
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