设计模式课程 设计模式精讲 16-5 代理模式源码解析

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();
        }
    }
}

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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);
    }
}