Detailed Introduction to Java Reflection Technology

Detailed Introduction to Java Reflection Technology Java reflection technology is a powerful and flexible feature in the Java language, providing the ability to inspect and manipulate classes, methods, fields, and constructors at runtime. Through reflection, we can dynamically check and manipulate the properties and methods of classes without directly accessing the source code, thereby achieving some flexible and dynamic functions. The core class of reflection is a set of classes under the java. lang. reflect package, including Class, Method, Field, Constructor, and so on. These classes allow us to obtain class information, manipulate methods and fields, and create instances of the class through a series of methods. Here are some common use cases of Java reflection technology: 1. Obtain class information: Using reflection can obtain information such as class names, modifiers, parent classes, interfaces, constructors, methods, and fields. By calling methods of the Class class, such as getName(), getModifiers(), getSuperclass(), etc., we can dynamically obtain the metadata of the class. Example code: Class<?> clazz = MyClass.class; String className = clazz.getName(); int modifiers = clazz.getModifiers(); Class<?> superClass = clazz.getSuperclass(); 2. Create instances of classes: Through reflection, we can dynamically create instances of classes at runtime. The newInstance() method of the Constructor class can be used to call the class's constructor to create a new instance. Example code: Class<?> clazz = MyClass.class; Constructor<?> constructor = clazz.getConstructor(); Object instance = constructor.newInstance(); 3. Method for calling objects: Reflection can be used to dynamically call methods on objects. Using the invoke() method of the Method class, we can pass object instances and method parameters to call the method. Example code: Class<?> clazz = MyClass.class; Method method = clazz.getMethod("myMethod", int.class, String.class); Object instance = clazz.newInstance(); Object result = method.invoke(instance, 10, "Hello"); 4. Obtain and set the field values of an object: Reflection can also be used to obtain and set the field values of an object. By using the get() and set() methods of the Field class, you can obtain and set the values of the fields. Example code: Class<?> clazz = MyClass.class; Field field = clazz.getField("myField"); Object instance = clazz.newInstance(); Object value = field.get(instance); field.set(instance, "New Value"); It should be noted that as reflection is an advanced technology, it may affect performance and security. When using reflection, careful consideration should be given to its usage scenario and abuse should be avoided.