Among software design patterns, the proxy pattern is a common design pattern that provides a way to separate access to an object from the specific implementation of the object. The proxy mode can be divided into two types: static proxy and dynamic proxy. They have significant differences in implementation mechanisms, usage scenarios, advantages and disadvantages, etc.

This article will explore the choices and differences between static and dynamic proxies in detail so that readers can better understand and apply these two proxy modes.

1. Static proxy

Static proxy is a simple implementation of the proxy pattern, which usually implements the same interface between the proxy class and the proxy class, and the proxy class holds a reference to the proxy class object. 

When the client calls a method of the proxy class, the proxy class will forward the request to the proxy class object and add some additional processing logic if necessary.

The implementation of static proxy is relatively simple, the code is more readable, and it is suitable for some simple scenarios. However, static proxies also have some limitations. First of all, if there are many proxy classes, then a corresponding proxy class needs to be written for each proxy class, which will lead to an increase in the amount of code and redundancy.

Secondly, static proxy usually need to modify the code of the proxy class when the proxy logic changes, which violates the "open-close principle", that is, the software entity should be open to expansion and closed to modification.

2. Dynamic proxy

Dynamic proxy is a technology that dynamically generates proxy classes at runtime. It uses Java's reflection mechanism to dynamically generate a proxy class based on the specified interface at runtime, and forwards the request to the proxy class object.

Dynamic proxy does not require writing a special proxy class for each proxy class, so it can greatly reduce the amount of code and improve code reusability.

The implementation of dynamic proxy is relatively complex, but it has higher flexibility and scalability. It can dynamically change the proxy logic according to different needs without modifying the code of the proxy class. In addition, dynamic proxy can also easily implement some common proxy logic, such as logging, performance monitoring, etc.

However, dynamic proxies also have some limitations. First, it requires that the proxied class must implement one or more interfaces, otherwise the proxy class cannot be generated. 

This limits the application of dynamic proxies in some scenarios. Secondly, because dynamic proxies rely on the reflection mechanism, they may be slightly inferior to static proxies in performance.

3. Selection of static proxy and dynamic proxy

When choosing between using a static proxy or a dynamic proxy, you need to weigh it based on specific scenarios and needs. Here are some suggestions:

If the number of proxy classes is small and the proxy logic is simple, you can consider using static proxy. The implementation of static proxy is simple and straightforward, easy to understand and maintain.

If the number of proxy classes is large, or the proxy logic needs to change frequently, it is recommended to use dynamic proxy. Dynamic proxies can reduce the amount of code and improve code reusability and scalability.

If the proxied class does not implement the interface, or the class that needs to be proxied is a class rather than an interface, then only static proxies can be used. Because dynamic proxies are implemented based on interfaces, classes that do not implement interfaces cannot be proxied.

When considering performance factors, if the proxy logic is executed very frequently and has strict performance requirements, you may need to consider a static proxy. While the performance penalty for dynamic proxies is not noticeable in most cases, it can become a bottleneck in extreme cases.

4. Summary

Static proxy and dynamic proxy are two common ways to implement proxy patterns. They have differences in implementation mechanisms, usage scenarios, advantages and disadvantages. When choosing which proxy mode to use, you need to weigh it based on specific scenarios and needs.

For simple scenarios and fixed proxy logic, static proxies may be a better choice; for complex scenarios and frequently changing proxy logic, dynamic proxies are more advantageous.

In practical applications, we can also combine other design patterns and technical means to further optimize the implementation of the proxy pattern.

For example, you can use the factory pattern to manage the creation process of proxy classes to improve code reusability and maintainability; you can also use AOP (aspect-oriented programming) technology to implement common proxy logic across multiple classes and reduce code coupling. Spend.

In short, the proxy pattern is a powerful design pattern that can help us separate object access and specific implementation, and improve the flexibility and scalability of the code. By in-depth understanding of the differences and choices between static and dynamic proxies, we can better apply this design pattern and bring greater value to software design and development.