Some of these methods are: forName() method: The Class class has a wide variety of methods that are useful in obtaining a reflection of the class executing and performing a wide range of actions with that class. Using an instance of Class, we can view, analyse and modify the attributes of a class while it is running, and can even invoke methods of that class. An instance of the class Class is used to represent both classes and interfaces in a Java application which is running. The Class is a final class in the java.lang package of Java’s standard library, and extends the Object class which forms the basis of all classes in java. Now that we have had an overview of the basic idea of Reflection, let us go through the class which plays the most significant role in reflection in java. Exposure of Internal Fields and Attributesĭue to the ability of Reflection API to access private members and invoke private functions, the internal details of classes and entities are exposed to the outside world and defeats the purpose of Abstraction in object oriented concepts, which may be seen as a violation of object oriented programming concepts. Also, the security permission requirements can pose a threat to code residing in a secure system. Reflection API requires cetain security permissions that are not available during execution under a securely managed system. As it tends to slow down processing, it isn’t recommended for use in sections of code that require high availability and low turnaround. This is because many functionalities make use of dynamic resolution which prevents to the use of certain Virtual machine optimisations. The use of reflection API can lead to high performance overhead and lead to lower performance. Inspite of being an extremely powerful tool, Reflection API and its usage does have a set of disadvantages such as, Low Performace Debugging and Testing toolsĭebugging requires the ability to view internal details of a class which include its private members.Debugging and Testing tools may use reflection to make systematic invocations to the classes by use of reflection and ensure test case coverage. Using these, the visual development environments make the information of the classes readily available to the user so that they can write proper code. IDEs, especially those which are capable of visual development, such as Eclipse or Netbeans, and class browsers can make extensive use of Reflection. Using the concepts of reflection, a programmer can make use of externally available user-defined classes by creating instances of those extensible objects by using their fully qualified name Developing IDEs and Class Browsers Other than these, the class is one of the most important classes in use for Reflection as the objects of Class can store the actual information of the class that we want to investigate or reflect. This class allows the programmer to dynamically create and manipulate Arrays This class provides information regarding the constructors of the class being reflected and inspected. This class provides information about the methods of the class being reflected and inspected. This class supports the dynamic proxy classes Method This class provides information about the class and other members’ access modifiers of the class being reflected. This class provides information about the fields present in the class whose reflection is being looked at. Let us have a look at some of the classes within the package Field It contains several interfaces and classes which define methods that are used for reflection of other classes. The core collection of classes and information related to Reflection in Java is encapsulated as the package. Reflection is heavily used in Java frameworks such as Spring, Hibernate, Junit etc. Using the concept of Reflection, a programmer can now manipulate all attributes of a class – including its methods, constructors, and fields even at runtime, and even invoke methods of that class and get a complete snapshot of it. In Java, the process of analyzing, viewing and modifying all the internal attributes, behaviors and capabilities of a class at runtime is called Reflection. Exposure of Internal Fields and Attributes.In the java.instrument module, the Instrumentation class has added a new redefineModule method since Java 9. Otherwise, it will lead to an IllegalCallerException.Īnother way to add opens to the target module is using the Java agent. This method will succeed only when we call it from the module being modified, from the modules it has granted open access to, or from the unnamed module. One thing to note: the Module.addOpens method is caller-sensitive. In the above code snippet, the srcModule opens the “ ” package to the targetModule. To add opens at runtime, we can use the Module.addOpens method: srcModule.addOpens("", targetModule)
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