Research and practice of CGLIB NODEP framework technical principles
Research and practice of CGLIB NODEP framework technical principles
introduction:
CGLIB is a powerful, high -performance code generation library, which is widely used in the Java project.There are CGLIB applications in many common frameworks such as Spring and Hibernate.Nodep is a lightweight version of CGLIB, which removes dependence on ASM, making it easier to integrate and use.This article will explore the technical principles of the CGLIB NODEP framework, help readers understand the implementation mechanism behind it, and provide some Java code examples.
text:
1. What is the CGLIB NODEP framework?
The CGLIB Nodep framework is a lightweight version based on the CGLIB library.CGLIB is a code generating library based on the ASM bytecode operating library, which is used to expand the Java class during runtime.However, as a bytecode operating library, ASM may have some complexity and difficulties in use.In order to reduce the difficulty of use, the Nodep version removes the dependence on ASM and provides a more concise and easy -to -use API.
2. The implementation principle of CGLIB NODEP
The implementation principle of the CGLIB Nodep framework mainly involves two core concepts, namely the "Enhancer" (enhancer) and "callback".
2.1 Enhancer (enhancer)
Enhancer is one of the core categories of the CGLIB Nodep framework, which is responsible for generating proxy classes during runtime.Enhancer creates a subclass to achieve proxy by inheriting the target class.When generating a proxy class, Enhancer will intercept the method of the agent class so that the corresponding logic can be performed when the method calls.
Here are a simple Java code example to demonstrate how to use Enhancer to create proxy classes:
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(TargetClass.class);
enhancer.setCallback((MethodInterceptor) (obj, method, args, proxy) -> {
System.out.println("Before method: " + method.getName());
Object result = proxy.invokeSuper(obj, args);
System.out.println("After method: " + method.getName());
return result;
});
TargetClass proxy = (TargetClass) enhancer.create();
proxy.someMethod();
In the above code, Enhancer sets the target class by calling the `setsuperclass` method, and then set a method interceptor through the` setcallback` method.Methods can execute additional logic before and after the method call.Finally, generate an agent object by calling the `Create` method.
2.2 Callback (callback)
Callback is another important concept of the CGLIB NODEP framework.It defines the logic of specific execution in the proxy class.CGLIB Nodep provides multiple types of callbacks, including Methodinterceptor, Noop, Lazyloader, etc.
-MethodInterceptor: Execute additional logic before and after the method call, which can modify, replace, and block the execution of the original method.
-Noop: without any operation, return to the original.
-Lazyloader: Using a delay loading method, the object initializes the object only when accessing.
Below is an example of using MethodinterCeptor:
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(TargetClass.class);
enhancer.setCallback((MethodInterceptor) (obj, method, args, proxy) -> {
if (method.getName().equals("someMethod")) {
System.out.println("Before method: " + method.getName());
Object result = proxy.invokeSuper(obj, args);
System.out.println("After handling method: " + method.getName());
return result;
}
return proxy.invokeSuper(obj, args);
});
TargetClass proxy = (TargetClass) enhancer.create();
proxy.someMethod();
In the above code, we decide whether the method name is `Somethod` to decide special processing of this method.Other methods will execute the original method by calling the `Proxy.invokesuper (OBJ, ARGS)`.
3. The actual application of CGLIB NODEP
The actual application of CGLib Nodep is very wide, especially in the development of the framework.Here are some common application scenarios:
3.1 dynamic proxy
CGLib Nodep can be used to achieve dynamic proxy, generate proxy objects for target class, and perform additional logic before and after method calls.This provides a convenient way to implement it for AOP (programming).
3.2 Object level cache
By using the Lazyloader callback, CGLIB Nodep can achieve a delayed loading and cache mechanism based on object -level.Only when the real access object can be initialized or obtained from the cache.
3.3 Object tracking and monitoring
CGLIB Nodep can be tracked and monitored by the MethodInterceptor callback in the agency class.By calling the relevant information before and after the method call, it can be used for log records, performance analysis, etc.
in conclusion:
Through this article, we understand the technical principles and practical applications of the CGLIB Nodep framework.As the lightweight version of CGLib Nodep, CGLIB Nodep removes dependence on ASM and simplifies the use of developers.We hope that this article can help readers more deeply understand the implementation mechanism behind CGLib Nodep and be able to apply it flexibly in actual projects.
