The technical principles of the CGLIB NODEP framework in the Java library
CGLIB is a powerful Java code generating library, which is widely used in the Java library.This article will explore the technical principles of the CGLIB NODEP framework in detail and provide relevant Java code examples.
1. CGLib Nodep framework Overview
CGLIB is a high -performance code generating library based on bytecode operation, which allows expansion of the Java class and realizing dynamic proxy during runtime.The CGLIB Nodep framework is an independent module of CGLib. It does not depend on any third -party library and can be used alone.
2. Technical principle introduction
The core technical principle of the CGLIB Nodep framework is through bytecode generation and class loading technology to dynamically generate subclasses to expand or modify the Java class.It mainly involves the following key concepts:
2.1 bytecode generation
CGLIB uses ASM library to directly generate the byte code, and operates the structure of the class through the access mode.Developers can use API provided by CGLIB to create objects such as ClassWriter, Methodvisitor, and use these objects to generate new classes or modify existing types of bytecode.
2.2 Class load and conversion
The CGLIB Nodep framework needs to be loaded into the JVM and was called through bytecode generating technology.CGLIB uses a custom classloader to load the generated subclasses, and calls the original class method to the subclass through bytecode enhanced technology.
2.3 Interceptor and Method Agency
Another core concept of the CGLib Nodep framework is the interceptor and method proxy.The interceptor is a class that implements the callback interface, which can insert additional logic before and after the target method execute.Method agent is actually a subclass of the target class, rewritten the method of the target class, and calls the logic of the interceptor at the right time.
3. CGLib Nodep framework application example
Below is a simple example that demonstrates the application of the CGLIB NODEP framework:
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
public class CGLibExample {
public static void main(String[] args) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(UserService.class);
enhancer.setCallback(new UserServiceInterceptor());
UserService userService = (UserService) enhancer.create();
userService.createUser("John");
}
static class UserService {
public void createUser(String name) {
System.out.println("Creating user: " + name);
}
}
static class UserServiceInterceptor implements MethodInterceptor {
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println("Before creating user");
Object result = proxy.invokeSuper(obj, args);
System.out.println("After creating user");
return result;
}
}
}
In this example, we define an UserService class with a CreateUser method for creating users.Then, we use the CGLIB's Enhancer class to create an agent object of UserService, and set the callback function to use the userviceInterceptor.In the Internet method, we inserted additional logic before and after the interceptor execute.After executing the main method, you can see the corresponding logs before creating users.
Summarize:
This article analyzes the technical principles of the CGLIB Nodep framework in the Java class library in detail, and gives a simple example code to illustrate its application.By using the CGLIB Nodep framework, developers can realize the function of similar dynamic proxy and modify or extend the Java class in a high -performance manner.
