Use CGLIB NODEP to write the technical principles of Java library analysis

Use CGLIB NODEP to write the technical principles of Java library analysis CGLIB is a powerful code generation library. It uses Java bytecode to operate technology to dynamically generate class and agent objects during runtime.The Nodep version of CGLIB is an unreasonable version, which means that it can be used independently without relying on other class libraries. The NodeP version of CGLIB is mainly based on ASM (Java bytecode operation framework) to operate Java bytecode.By dynamically generating the Java bytecode, new classes and related methods can be generated at runtime to achieve functions such as AOP (facing surface programming) and dynamic proxy.This allows Java developers to modify and enhance the class more flexibly without modifying the source code. Let's analyze the technical principles of CGLib Nodep to write the Java class library: 1. Introduce the CGLib Nodep Library: Introduce the CGLIB Nodep Library in the Java project to use the code generation function.You can add it to the dependence of the project by Maven or manually downloading the jar package. 2. Create an ENHANCER object: ENHANCER is the main class used to generate agents and subclasses in CGLIB.By creating an enhancer object, we can set information such as loaders, father -class, callbacks and other information to control the behavior of generating classes. Enhancer enhancer = new Enhancer(); enhancer.setClassLoader(MyClassLoader.class.getClassLoader()); enhancer.setSuperclass(MyClass.class); enhancer.setCallback(new MyMethodInterceptor()); 3. Set up callback: The callback is the code executed when the specific method is called in the generated class.You can realize the custom MethodInterCePTOR interface, and define specific logic by rewriting the intercept method.In the intercept method, we can insert other code before and after the method execution to enhance the method. public class MyMethodInterceptor implements MethodInterceptor { @Override public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable { // Insert the code before the method execution System.out.println("Before method execution!"); // Call the original method Object result = proxy.invokeSuper(obj, args); // Insert the code after the method executes System.out.println("After method execution!"); return result; } } 4. Generate class: By calling the Create method, we can generate a new class or agent object. MyClass myObject = (MyClass) enhancer.create(); When running, CGLIB dynamically generates bytecode based on the set parent class, interface, and callback information, and loads it to JVM.The generated class has the same methods and attributes as the parent class, and can achieve additional logic according to the callback code. To sum up, the technical principles of writing the Java class library using CGLIB NODEP are achieved by using byte code operation technology.With the powerful function of CGLIB, we can generate new classes and agent objects at runtime, and insert custom code in the generated class to achieve modification and enhancement of classes.This technology is very useful in AOP and dynamic agents, which can make the Java program more flexible and scalable.