In the world of software development, the proxy pattern is a common design pattern that allows one class to represent the functionality of another class. This representation process can include additional operations such as access control, logging, or transaction processing.

There are two main types of proxy modes: static proxy and dynamic proxy. These two proxy methods are significantly different in principle, implementation, and usage scenarios. This article will explain in detail the difference between static and dynamic proxies, and how to choose which one to use.

1. Static proxy

Static proxy means that the proxy class is defined in advance in the code, and the proxy class and the proxy class are determined at compile time. It usually implements the proxy function by implementing the same interface as the proxy class, holding an instance of the proxy class in the proxy class, and calling methods of the proxy class.

The advantage of static proxy is that it is simple to implement and easy to understand.

Since the proxy class and the proxy class are determined at compile time, the performance overhead is relatively small. However, the disadvantage of static proxy is also obvious, that is, if methods are added to the interface, both the proxy class and the proxy class need to be modified synchronously, which increases the maintenance cost of the code.

In addition, when a large number of classes need to be proxied, static proxies will cause a large number of proxy classes to be created, which will also increase the complexity of the code.

2. Dynamic proxy

Dynamic proxy dynamically generates proxy classes at runtime, and the relationship between the proxy class and the proxy class is determined at runtime. Java's dynamic proxy is mainly implemented using Java's reflection mechanism. The proxy class calls the method of the proxy class by implementing the InvocationHandler interface and overriding the invoke method.

The advantage of dynamic proxies is their flexibility.

Since the proxy class is dynamically generated at runtime, it can easily handle situations where a large number of classes need to be proxied. In addition, when methods are added to the interface, the proxy class does not need to be modified, only the proxied class needs to be modified, which greatly reduces the maintenance cost of the code.

However, dynamic proxy also has some disadvantages, such as relatively large performance overhead (because it involves reflection), and it can only proxy classes that implement interfaces (it cannot proxy classes without interfaces).

3. How to choose

When choosing between using a static proxy or a dynamic proxy, we need to consider the following aspects:

Performance requirements

If the system has high performance requirements and the number of proxied classes is small, static proxies may be a better choice. Because the static proxy has determined the relationship between the proxy class and the proxy class during compilation, the performance overhead is relatively small. On the contrary, if the system does not have particularly high performance requirements and the number of proxied classes is large, then dynamic proxy may be more suitable.

Maintenance cost

If the interface changes frequently, or there are many classes that require proxies, then using dynamic proxies can greatly reduce code maintenance costs. Because dynamic proxy does not need to modify the proxy class when the interface changes, it only needs to modify the proxy class. In addition, dynamic proxies can easily handle situations where a large number of classes need to be proxied.

Implementation complexity

The implementation of static proxies is relatively simple and easy to understand. The implementation of dynamic proxy is relatively complex and requires the use of Java's reflection mechanism. Therefore, if the project team does not understand the reflection mechanism enough, or the project has high requirements for code legibility, it may be more inclined to choose a static proxy.

Special needs

If some classes do not implement the interface but still need to be proxied, then static proxies cannot meet this demand, and dynamic proxies can only be selected at this time. Because dynamic proxy implements the proxy function by implementing the InvocationHandler interface and overriding the invoke method, it does not depend on whether the proxied class implements the interface.

Summarize

To sum up, static proxy and dynamic proxy each have their own advantages and disadvantages. Which one to use needs to be decided based on the actual needs of the project. In actual development, we can comprehensively consider the project's performance requirements, maintenance costs, implementation complexity, and special needs to select the most appropriate proxy method.