设计模式课程 设计模式精讲 16-5 代理模式源码解析

Posted 2022-11-17 1446358788-qq

1　　　　源码解析

1.1　　　　源码解析1（jdk中的应用）

1.2　　　　源码解析2（spring中的应用）

1.3　　　　源码解析3（mybaties中的应用）

 

 

 

1　　　　源码解析

1.1　　　　源码解析1（jdk中的应用）

java.lang.reflect.Proxy

public class Proxy implements java.io.Serializable 
    protected Proxy(InvocationHandler h) 
        doNewInstanceCheck();
        this.h = h;
    

//此处产生一个新的实例（目标对象）
public static Object newProxyInstance(ClassLoader loader,
                                          Class<?>[] interfaces,
                                          InvocationHandler h)
        throws IllegalArgumentException
    
        if (h == null) 
            throw new NullPointerException();
        

        final Class<?>[] intfs = interfaces.clone();
        final SecurityManager sm = System.getSecurityManager();
        if (sm != null) 
            checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
        

        /*
         * Look up or generate the designated proxy class.
         */
        Class<?> cl = getProxyClass0(loader, intfs);

        /*
         * Invoke its constructor with the designated invocation handler.
         */
        try 
            final Constructor<?> cons = cl.getConstructor(constructorParams);
            final InvocationHandler ih = h;
            if (sm != null && ProxyAccessHelper.needsNewInstanceCheck(cl)) 
                // create proxy instance with doPrivilege as the proxy class may
                // implement non-public interfaces that requires a special permission
                return AccessController.doPrivileged(new PrivilegedAction<Object>() 
                    public Object run() 
                        return newInstance(cons, ih);
                    
                );
             else 
                return newInstance(cons, ih);
            
         catch (NoSuchMethodException e) 
            throw new InternalError(e.toString());
        
    

 

1.2　　　　源码解析2（spring中的应用）

ProxyFactoryBean

public class ProxyFactoryBean extends ProxyCreatorSupport implements FactoryBean<Object>, BeanClassLoaderAware, BeanFactoryAware     
    
   //如果不声明，默认单例对象，注解声明多例，则声明多例对象
　　public Object getObject() throws BeansException 
        this.initializeAdvisorChain();
        if (this.isSingleton()) 
            return this.getSingletonInstance();
         else 
            if (this.targetName == null) 
                this.logger.warn("Using non-singleton proxies with singleton targets is often undesirable. Enable prototype proxies by setting the ‘targetName‘ property.");
            

            return this.newPrototypeInstance();
        
    

 

 

1.3　　　　源码解析3（mybaties中的应用）

MapperProxyFactory

public class MapperProxyFactory<T> 
　　public T newInstance(SqlSession sqlSession) 
        MapperProxy<T> mapperProxy = new MapperProxy(sqlSession, this.mapperInterface, this.methodCache);
        return this.newInstance(mapperProxy);