master-cglib-in-java

You are not a drop in the ocean, you are the entire ocean in a drop.

What’s CGLIB

CGLIB (Code Generation Library) is a Java library used for generating dynamic proxy classes and enhancing Java classes at runtime. It is an open-source library developed by CGLIB team and is widely used in Java frameworks such as Spring, Hibernate, and others.

CGLIB provides a way to generate classes dynamically by extending the functionality of Java’s reflection API. With CGLIB, developers can create proxy classes that intercept method invocations and perform additional actions before or after invoking the method. This is useful for implementing features such as caching, logging, and security checks in Java applications.

CGLIB is often used in conjunction with other Java frameworks, such as Spring, to provide additional functionality to applications. For example, in Spring, CGLIB is used to create proxy classes for beans that have been marked with certain annotations, such as @Transactional.

Overall, CGLIB is a powerful library for generating dynamic proxies and enhancing Java classes at runtime, and it is widely used in Java development.

How to use CGLIB

To use CGLIB in a Java project, you need to follow these steps:

Add CGLIB to your project’s dependencies. You can do this by adding the following dependency to your project’s build file (e.g. pom.xml for Maven):

<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>3.3.0</version>
</dependency>

Create a class that will be enhanced by CGLIB. This class should have at least one method that you want to intercept. For example:

public class MyClass {
    public void myMethod() {
        System.out.println("MyClass.myMethod() called");
    }
}

Create an interceptor class that will intercept method invocations on your enhanced class. This class should extend MethodInterceptor from CGLIB. For example:

import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;

public class MyInterceptor implements MethodInterceptor {
    public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
        System.out.println("Before " + method.getName() + " method call");
        Object result = proxy.invokeSuper(obj, args);
        System.out.println("After " + method.getName() + " method call");
        return result;
    }
}

Use CGLIB to enhance your class with the interceptor. To do this, create an instance of Enhancer from CGLIB, set the class to be enhanced, and set the interceptor. Then call create() method to generate the enhanced class. For example:

import net.sf.cglib.proxy.Enhancer;

public class Main {
    public static void main(String[] args) {
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(MyClass.class);
        enhancer.setCallback(new MyInterceptor());
        MyClass myClass = (MyClass) enhancer.create();
        myClass.myMethod();
    }
}

When you run the main() method, it will create an instance of MyClass enhanced with the interceptor MyInterceptor. When you call myMethod() on the enhanced instance, it will first call the interceptor’s intercept() method, which will print a message before and after the method call, and then delegate to the original method implementation.

Note that CGLIB can also be used to generate dynamic proxies for interfaces. In that case, you should use Enhancer.create() method with the interface class instead of setSuperclass().

1. –HTH–