设计模式总结

工厂模式

只对结果负责，封装创建过程，如BeanFactory

    Object getBean(String name) throws BeansException;

单例模式

保证独一无二，如ApplicationContext

原型模式

拔一根猴毛，吹出千万个，如BeanUtils

    public static void copyProperties(Object source, Object target) throws BeansException {
        copyProperties(source, target, null, (String[]) null);
    }

代理模式

招人办事，增强职责，如JdkDynamicAopProxy

final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializable {

    @Override
    public Object getProxy(@Nullable ClassLoader classLoader) {
        if (logger.isDebugEnabled()) {
            logger.debug("Creating JDK dynamic proxy: target source is " + this.advised.getTargetSource());
        }
        Class[] proxiedInterfaces = AopProxyUtils.completeProxiedInterfaces(this.advised, true);
        findDefinedEqualsAndHashCodeMethods(proxiedInterfaces);
        return Proxy.newProxyInstance(classLoader, proxiedInterfaces, this);
    }

    @Override
    @Nullable
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        MethodInvocation invocation;
        Object oldProxy = null;
        boolean setProxyContext = false;

        TargetSource targetSource = this.advised.targetSource;

还有CglibAopProxy

class CglibAopProxy implements AopProxy, Serializable {

      //...

    private static class StaticUnadvisedInterceptor implements MethodInterceptor, Serializable {
        @Override
        @Nullable
        public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
            Object retVal = methodProxy.invoke(this.target, args);
            return processReturnType(proxy, this.target, method, retVal);
        }
      //...

     private static class EqualsInterceptor implements MethodInterceptor, Serializable {
        @Override
        public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) {
            Object other = args[0];
            if (proxy == other) {
                return true;
            }
            if (other instanceof Factory) {
                Callback callback = ((Factory) other).getCallback(INVOKE_EQUALS);
                if (!(callback instanceof EqualsInterceptor)) {
                    return false;
                }
                AdvisedSupport otherAdvised = ((EqualsInterceptor) callback).advised;
                return AopProxyUtils.equalsInProxy(this.advised, otherAdvised);
            }
            else {
                return false;
            }
        }

    //...

委派模式

干活算你的（普通员工），功劳算我的（项目经理），如DispatcherServlet

@Nullable
    protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
        if (this.handlerMappings != null) {
            for (HandlerMapping hm : this.handlerMappings) {
                if (logger.isTraceEnabled()) {
                    logger.trace(
                            "Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
                }
                HandlerExecutionChain handler = hm.getHandler(request);
                if (handler != null) {
                    return handler;
                }
            }
        }
        return null;
    }

还有BeanDefinitionParserDelegate

模板模式

在Spring的AbstractApplicationContext.java中，refresh()是典型的模板模式，代码如下

@Override
    public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            //1.调用容器准备刷新的方法，获取容器的当时时间，同时给容器设置同步标志
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            //2.告诉子类启动refreshBeanFactory()方法，Bean定义资源文件的载入，从子类的refreshBeanFactory()方法启动
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            //3.为BeanFactory配置容器特性，例如类加载器、事件处理等
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                registerBeanPostProcessors(beanFactory);

    

还有JdbcTemplate、HttpServlet

适配器模式

兼容转换头，如AdvisorAdapter、HandlerAdapter

    boolean supportsAdvice(Advice advice);
    MethodInterceptor getInterceptor(Advisor advisor);

装饰器模式

包装，同宗同源，如BufferdReader、InputStream、OutputStream、HttpHeadResponseDecorator

public class BufferedReader extends Reader {

//...
    public BufferedReader(Reader in, int sz) {
        super(in);
        if (sz <= 0)
            throw new IllegalArgumentException("Buffer size <= 0");
        this.in = in;
        cb = new char[sz];
        nextChar = nChars = 0;
    }

观察者模式

任务完成时通知，如ContextLoaderListener