The implementation principle of CGLIB dynamic proxy in Java
The implementation principle of CGLIB dynamic proxy in Java
introduction:
In Java, dynamic proxy is a very common design pattern that allows us to dynamically create proxy classes at runtime to replace the function of the original object.Java provides two dynamic proxy implementation methods, one is an interface -based JDK dynamic agent, and the other is a class -based CGLIB dynamic agent.This article will focus on the implementation principle of CGLIB dynamic proxy and provide the corresponding Java code example.
1. Introduction to CGLIB dynamic agency:
CGLIB (Code Generation Library) is an open source code generating library. It acts as an agent by generating a subclass of the target class.Unlike the JDK dynamic proxy, the CGLIB dynamic proxy does not require the target class to implement the interface, so it can be represented by those classes that do not provide interfaces.
2. The implementation principle of CGLIB dynamic proxy:
The implementation principle of CGLIB dynamic proxy mainly involves two core categories: Enhancer and MethodInterCector.
-The Enhancer class is responsible for generating subclasses of the target class and realizing actual proxy logic.
The steps of CGLIB dynamic proxy are as follows:
Step 1: Create an enhancer object and set the proxy target class and Methodinterceptor.
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(TargetClass.class);
enhancer.setCallback(new CustomMethodInterceptor());
Step 2: The instance of the proxy class is generated through the `Create () method of the enhancer object.
TargetClass proxy = (TargetClass) enhancer.create();
Step 3: Call the proxy method method to trigger the enhanced logic defined in the MethodInterCector.
proxy.doSomething();
3. Java code example:
In the next example, we will create a simple target class `targetClass`, which contains a` dosomething () method.We will then use the CGLIB dynamic agent to create its proxy classes and add some additional operations when calling the proxy method.
First, we need to add CGLIB dependence.It can be implemented by adding the following code to the pom.xml file of the Maven project::
<dependencies>
<dependency>
<groupId>cglib</groupId>
<artifactId>cglib</artifactId>
<version>3.3.0</version>
</dependency>
</dependencies>
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 CGLibDynamicProxyExample {
public static void main(String[] args) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(TargetClass.class);
enhancer.setCallback(new CustomMethodInterceptor());
// Step 2: In examples
TargetClass proxy = (TargetClass) enhancer.create();
// step 3: Call the proxy method method to trigger the enhanced logic defined in MethodInterCepptor
proxy.doSomething();
}
}
public class TargetClass {
public void doSomething() {
System.out.println("Doing something...");
}
}
public class CustomMethodInterceptor implements MethodInterceptor {
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println("Before method execution");
Object result = proxy.invokeSuper(obj, args);
System.out.println("After method execution");
return result;
}
}
In the above example, the `CustomMethodInterceptor` realizes the` Methodinterceptor` interface, and defines the operation of the operation before and after calling the proxy method in the `intercept` method.
When we run the example code, the output result will be shown below:
Before method execution
Doing something...
After method execution
Through the above examples, we can clearly see how the CGLIB dynamic proxy generates an agent class during runtime, and uses the enhanced logic defined by the `MethodInterCePTor` interface.
in conclusion:
CGLIB dynamic proxy is a class -based proxy implementation method, allowing us to dynamically create the proxy object of the target class during runtime.It generates enhanced logic provided by the target class and uses the enhanced logic provided by the `MethodinterCepptor` interface to add additional operations when calling the method.This powerful function makes the CGLIB dynamic proxy a ideal choice for AOP (cutting surface programming) in Java.
