Reveal the technical principles of the CGLIB NODEP framework in the Java class library
CGLIB (Code Generation Library) is a powerful third -party Java bytecode generating library, which is widely used in many Java libraries.CGLIB Nodep is a variant of CGLib. It is part of the core code of CGLIB, which provides basic functions without relying on other external libraries.
The principles of CGLIB NODEP mainly include dynamically generating bytecode, inheritance or proxy target, method interception and object generation.
First, CGLIB Nodep uses Java's reflection mechanism to dynamically generate byte code.By analyzing the structure of the target class, CGLIB can generate new classes or modify the existing type byte code.The ability to generate byte code is the core of CGLIB NODEP.
Next, CGLib Nodep enhance its functions by inheriting or proxy target categories.By creating a subclass of a target class, CGLIB NODEP can inherit the attributes and methods of the target class, and can add additional logic to the subclass.This inheritance method enables the CGLIB Nodep to enhance the function by replacing the target class.
On the basis of inheritance or proxy, CGLIB NODEP can intercept the method of the target class.By adding additional codes to the generated bytecode, CGLIB NODEP can be used before, then or instead of the original method to perform additional operations before the target class is called.This method intercepts enables the CGLIB Nodep to enhance its method without modifying the source code of the target category.
Finally, CGLib Nodep also provides the function of object generation.By specifying the constructor and parameters of the target class, CGLIB Nodep can instantiate the object of the target class, and it can initialize the attribute assignment and other initialization operations.The function generated by this object enables CGLib Nodep to dynamically generate objects during runtime, thereby meeting more flexible needs.
The following is a simple example of using CGLIB NODEP:
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.proxy.Enhancer;
public class Main {
public static class TargetClass {
public void doSomething() {
System.out.println ("Original Method: Dosomething");
}
}
public static class MyInterceptor implements MethodInterceptor {
@Override
public Object intercept(Object obj, java.lang.reflect.Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println ("front operation");
Object result = proxy.invokeSuper(obj, args);
System.out.println ("rear operation");
return result;
}
}
public static void main(String[] args) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(TargetClass.class);
enhancer.setCallback(new MyInterceptor());
TargetClass proxy = (TargetClass) enhancer.create();
proxy.doSomething();
}
}
In the above example, we define a target class `targetClass`, one of which is a` dosomething` method.Then, we created a `MyInterceptor` class that implemented the` MethodinterCepTor` interface to intercept and enhance the target method.In the `Main` method, we use CGLIB's` Enhancer` class to generate the subclass of the target class, and specify the interceptor to be `MyInterCepTor`.Finally, when the created proxy object `proxy` is called to call the` dosomething` method, the front operation and rear operation of the interceptor will be automatically triggered.
In summary, the CGLIB NODEP framework is a dynamically generated technical principles such as bytecode, inheritance or proxy target class, method intercepting and object generation to achieve enhanced and functional expansion of the Java library.It has very wide application value in many scenarios.
