Use CGLIB to implement common problems and solutions for dynamic proxy
Use CGLIB to implement common problems and solutions for dynamic proxy
In Java, dynamic proxy is a powerful mechanism that allows us to create proxy classes at runtime and forward the method call to actual objects.CGLIB is a commonly used open source library for dynamic proxy.This article will discuss the use of CGLIB to achieve common problems common to dynamic agents and provide solutions.
1. Unable to proxy the final class and methods
Problem description: CGLIB cannot represent the Final class and methods because they cannot be inherited or covered.
Solution: Before using CGLIB, you need to ensure that the target category and method are not final.If you need to act as a final class or method, you can consider using other dynamic proxy libraries, such as the JDK dynamic agent.
Example code:
public final class FinalClass {
public void finalMethod() {
System.out.println("Final method");
}
}
// Unable to use the CGLIB proxy FinalClass class, it will throw an exception
FinalClass proxy = (FinalClass) Enhancer.create(FinalClass.class, new YourMethodInterceptor());
2. Acting class appears ClassCastexception
Problem description: When creating a proxy class with CGLIB, ClassCastexception may appear abnormal, usually caused by type conversion errors.
Solution: Make sure the proxy type is correctly converted into the type of target class when calling the enhancer.create method.
Example code:
public class TargetClass {
public void targetMethod() {
System.out.println("Target method");
}
}
MethodInterceptor interceptor = new YourMethodInterceptor();
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(TargetClass.class);
enhancer.setCallback(interceptor);
// When creating a proxy class, correctly convert the type into the type of the target class
TargetClass proxy = (TargetClass) enhancer.create();
3. Unable to represent the static method
Problem description: CGLIB cannot represent the Static method because they do not belong to instance methods, but belong to the class method.
Solution: To proxy the Static method, you can consider using other dynamic proxy libraries, or to modify the byte code of the target class to achieve the goal.
Example code:
public class TargetClass {
public static void staticMethod() {
System.out.println("Static method");
}
}
// Unable to use the CGLIB proxy method method
TargetClass proxy = (TargetClass) Enhancer.create(TargetClass.class, new YourMethodInterceptor());
4. Unable to process cycle reference
Problem description: When the target class and proxy classes are cited, infinite recursive calls may be caused, and the StackoverFlowerror will eventually cause abnormalities.
Solution: Avoid circulating references when creating a proxy class.You can solve the problem of cycle reference by passing parameters or using dependency injection.
Example code:
public class TargetClass {
private ProxyClass proxy;
public void setProxy(ProxyClass proxy) {
this.proxy = proxy;
}
}
public class ProxyClass {
private TargetClass target;
public void setTarget(TargetClass target) {
this.target = target;
}
}
// Avoid circulating references
TargetClass target = new TargetClass();
ProxyClass proxy = new ProxyClass();
target.setProxy(proxy);
proxy.setTarget(target);
Summarize:
This article discusses the problems and solutions that use CGLIB to implement dynamic agents.Although CGLIB is a powerful library, it also has its restrictions.Before using CGLIB, you need to ensure that the target category and method are not final, and the type conversion must be properly handled.At the same time, pay attention to avoid circulating reference issues.By following these solutions, CGLIB can be used to achieve dynamic proxy.
