Java static proxy and dynamic proxy in-depth learning

1. Proxy mode
The proxy mode is a commonly used Java design pattern. The characteristic is that the proxy class and the delegation class have the same interface. The proxy class is mainly responsible for preprocessing messages for the delegation class, filtering messages, forwarding messages to the delegation class, and afterwards Process messages etc.
There is usually an association between proxy classes and delegate classes. An object of a proxy class is associated with an object of a delegate class. The object of the proxy class itself does not actually implement the service, but by calling the relevant methods of the object of the delegate class. to provide specific services.
According to the creation period of the agent, the agent class can be divided into two types:
Static proxy: Created by programmers or automatically generated by specific tools and then compiled. The .class file of the proxy class already exists before the program is run.
Dynamic proxy: dynamically created using the reflection mechanism when the program is running.

2. Single static proxy

码如下:
public interface CountDao 
{ 
// 查看账户方法 
public void queryCount(); 
} 
public class CountDaoImpl implements CountDao 
{ 
public void queryCount() 
{ 
System.out.println("查看账户方法..."); 
} 
} 
public class CountTrancProxy implements CountDao 
{ 
private CountDao countDao; 
public CountProxy(CountDao countDao) 
{ 
this.countDao = countDao; 
} 
@Override 
public void queryCount() 
{ 
System.out.println("tranc start"); 
countDao.queryCount(); 
System.out.println("tranc end"); 
} 
} 
public class TestCount 
{ 
public static void main(String[] args) 
{ 
CountTrancProxy countProxy = new CountTrancProxy(new CountDaoImpl()); 
countProxy.updateCount(); 
} 
}

tranc start
View account method...
tranc end
3. Multiple static proxies
Added

码如下:
public class CountLogProxy implements CountDao 
{ 
private CountDao countDao; 
public CountLogProxy(CountDao countDao) 
{ 
this.countDao = countDao; 
} 
@Override 
public void queryCount() 
{ 
System.out.println("Log start"); 
countDao.queryCount(); 
System.out.println("Log end"); 
} 
}

Log start
before transaction processing
based on the above code View account method...
After transaction processing
Log end
4. Summary
In fact, proxy classes can be used to achieve the effect of proxy by inheritance or interface implementation. However, when multiple proxy classes need to be combined with each other, inheritance is not flexible and proxy classes need to be constantly rewritten. The way to implement interfaces is to easily combine proxy classes through aggregation.