In -depth understanding of the Java reflection library and its working principle

In -depth understanding of the Java reflection library and its working principle introduction: In Java, the reflection mechanism is a powerful tool that allows the program to check and modify its own structure, attributes and behaviors during runtime.The reflex library in Java provides a set of APIs that enable developers to dynamically operate class, methods and fields, and in some cases, they can load and call these classes even if they cannot obtain class information during compilation.Essence 1. The principle of reflection The working principle of the Java reflection is to obtain the class information by analyzing the bytecode of the class during runtime.When the Java compiler compiles the Java source code into bytecode, a large amount of class information is retained in the class file, including the structure, methods and fields of the class.The reflex library uses the information saved in the class file to dynamically load and operate the operation. The Java reflection provides three core categories: Class, Constructor, and Method.The Class class represents the runtime type of a class, the constructor class represents the constructor of the class, and the method class represents the method of the Method class.Using these classes, we can get all the information of the class at runtime and modify and call. Second, the scene of using the Java reflection library 1. Dynamically load class to avoid hard coding when the class is determined during compilation 2. Get the structural information of the class during runtime and perform the corresponding operation 3. Create an instance of the class and operate its attributes 4. The method of calling the class, including private methods Third, the use of Java reflective library The following uses a few simple examples to illustrate how to use the Java reflection library: 1. Dynamic loading class and creating objects // Dynamic loading class Class<?> clazz = Class.forName("com.example.MyClass"); // Create an object instance Object obj = clazz.getDeclaredConstructor().newInstance(); 2. Get the field information and modify the attribute value // Get the field Field field = clazz.getDeclaredField("myField"); // Settable accessable field.setAccessible(true); // Modify the attribute value field.set(obj, "new value"); 3. Classification method // Method method = clazz.getDeclaredMethod("myMethod", String.class); // Settable accessable method.setAccessible(true); // Call method method.invoke(obj, "arg1"); Through the above examples, we can see that the Java reflection library allows us to load and operate the class dynamically during runtime.The reflection mechanism provides developers with greater flexibility and scalability, which can cope with various developments. in conclusion: The Java reflection library is a powerful tool that allows developers to check and modify the structure, attributes and behaviors of the class during runtime.Through the reflection mechanism, developers can dynamically load and operate the operation, so that the program has higher scalability and flexibility.However, the use of reflection also needs to be cautious, because reflection can lead to performance expenses, and it may also destroy packaging and safety.Therefore, the profit and disadvantages need to be weighing when using reflexes and choose according to the actual situation.