The technical principles and practice of the CGLIB NODEP framework
The technical principles and practice of the CGLIB NODEP framework
CGLIB is an open source byte code generating library that provides enhanced functions for Java applications by creating and modifying the byte code of the Java class.NODEP is an attached bag of the CGLIB library. It provides a streamlined version without any dependencies and can be used in the environment that cannot be introduced in other external dependencies.
The technical principles of the CGLIB Nodep framework are mainly based on Java bytecode operation and dynamic agency mechanism.It uses the ASM library to operate the byte code of the class file to enhance the class by creating and modifying the byte code.CGLIB can generate a subclass of a target class during runtime, and to achieve the interception and enhancement of the method by inheriting the target class and rewriting the method.
Below is a simple example of using the CGLIB NODEP framework, showing how to create a proxy class, intercept the method of target category, and add additional logic before and after the method execution:
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 Example {
public static void main(String[] args) {
// Create the target class
TargetClass target = new TargetClass();
// Create an enhancer object to generate proxy classes
Enhancer enhancer = new Enhancer();
// Set the target class as the parent class
enhancer.setSuperclass(TargetClass.class);
// Set the callback interface to intercept the target class
enhancer.setCallback(new MethodInterceptor() {
@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
// Method to add logic before execution
System.out.println("Before method execution");
// Call the target class method
Object result = proxy.invoke(target, args);
// Add logic after execution
System.out.println("After method execution");
return result;
}
});
// Create proxy objects
TargetClass proxy = (TargetClass) enhancer.create();
// The method of calling the proxy object
proxy.doSomething();
}
}
class TargetClass {
public void doSomething() {
System.out.println("Doing something...");
}
}
In the above example, we first created a target class `targetClass`, and then use the CGLIB's Enhancer object to generate the proxy class.By setting the target class as the parent class and the callback interface, we can intercept and enhance the target class in the agency class.In the `intercept` method of the callback interface, we can add additional logic before and after the method execution.
When we run the above example, the results will be output:
Before method execution
Doing something...
After method execution
It can be seen that when calling the `Dosomething` method of the proxy object, the proxy class successfully intercepts the method of the target class, and adds additional logic before and after the method execution.
Through the CGLIB Nodep framework, we can more conveniently implement the dynamic agent and enhancement of the Java class.It has a wide range of applications in many fields, such as AOP (facing surface programming), testing framework, persistence, etc.By being familiar with and mastering the technical principles and practice of the CGLIB Nodep framework, we can better use it to improve the functions and performance of the Java application.
