Detailed explanation of the technical principles of the CGLIB NODEP framework in the Java class library
CGLIB Nodep is a dynamic bytecode enhanced framework commonly used in the Java library. It generates dynamic expansion and enhance the target class by generating proxy classes.In this article, we will introduce the technical principles of the CGLIB NODEP framework in detail and provide some Java code examples.
CGLib Nodep is a high -performance bytecode processing framework based on ASM framework. It generates a proxy class by operating bytecode.Compared with the Java dynamic proxy framework, CGLIB NODEP can enhance the method of class, not just interfaces.This makes it very useful when AOP (facing surface programming).
The running process of the CGLIB NODEP framework can be divided into the following steps:
1. Find the target class: First of all, we need to find the target class that needs to be agent.This target class can be an ordinary Java class without implementing specific interfaces.
2. Create an enhancer object: ENHANCER is the core category of the CGLIB NODEP framework, which is used to generate an agent class.We need to create an enhancer object and set the target class as the parent class.
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(TargetClass.class);
3. Set the callback function: The callback function is a section of code used to execute when the target method is called.We can implement the custom METHODINTERCEPTOR interface and pass it as a callback function to the ENHANCER object.
enhancer.setCallback(new MyMethodInterceptor());
4. Generate proxy category: By calling the Create method of the ENHANCER object, CGLIB Nodep will generate a proxy byte code based on the target class and callback functions, and return an instance of the proxy class.
TargetClass proxy = (TargetClass) enhancer.create();
5. Call the proxy class method: Now we can use the generated proxy class to call the target class.When calling the proxy method method, CGLib Nodep will intercept the call of the target class method and execute the code in the setting function.
proxy.methodName();
Through the above steps, we can enhance it without modifying the source code of the target category.For example, we can add logistics and performance monitoring functions to the callback function.
The following is a complete example code, which demonstrates the use 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;
class TargetClass {
public void doSomething() {
System.out.println("TargetClass: Doing something...");
}
}
class MyMethodInterceptor implements MethodInterceptor {
@Override
public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
System.out.println("Before method: " + method.getName());
Object result = methodProxy.invokeSuper(o, objects);
System.out.println("After method: " + method.getName());
return result;
}
}
public class CGLibNodepExample {
public static void main(String[] args) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(TargetClass.class);
enhancer.setCallback(new MyMethodInterceptor());
TargetClass proxy = (TargetClass) enhancer.create();
proxy.doSomething();
}
}
In the above code, we created an ordinary Java class called TargetClass and set up a Dosomething method.Then, we created a MyMethodInterCeptor class as a callback function, and used Enhancer to generate targetClass's proxy classes.In the callback function, we added additional printing sentences before and after the goal.
When running the example code, the output result is as follows:
Before method: doSomething
TargetClass: Doing something...
After method: doSomething
It can be seen from the output results that CGLIB NODEP successfully intercepted the call of the target method and added additional logic before and after the method execution.
In summary, the CGLIB Nodep framework is used to generate the proxy class by operating bytecode to achieve dynamic expansion and enhance the target class.The principle is to create an enhancer object, set the target class and callback function, and then generate the byte code of the proxy class.This allows us to execute custom logic before and after the target class.
