分享我在阿里工作十年接触过Java框架设计模式一、前言二、责任链设计模式（Chain of Responsibility Pattern）三、工厂模式（Factory Pattern）四、单例设计模式

public void doFilter(ServletRequest request, ServletResponse response)
        throws IOException, ServletException {
        ...
        internalDoFilter(request,response);
        ...
    }

private void internalDoFilter(ServletRequest request, 
                                  ServletResponse response)
        throws IOException, ServletException {

        // Call the next filter if there is one
        if (pos < n) {

            //获取filter链中下标为pos的filter
            ApplicationFilterConfig filterConfig = filters[pos++];
            Filter filter = null;
            try {
                filter = filterConfig.getFilter();
                support.fireInstanceEvent(InstanceEvent.BEFORE_FILTER_EVENT,
                                          filter, request, response);

                if (request.isAsyncSupported() && "false".equalsIgnoreCase(
                        filterConfig.getFilterDef().getAsyncSupported())) {
                    request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR,
                            Boolean.FALSE);
                }

                ...

                //调用自定义filter的dofilter方法
                filter.doFilter(request, response, this);

                support.fireInstanceEvent(InstanceEvent.AFTER_FILTER_EVENT,
                                          filter, request, response);
            } 
            ....

    }
   .....
}

@Test
public void testBeanFactoy() throws NamingException, SQLException, ParseException, IOException {

    //创建Bean工厂
    DefaultListableBeanFactory bf = new DefaultListableBeanFactory();

    //给bean工厂添加bean定义,解析xml里面的bean放入bean工厂
    loadBeanDefinitions(bf);

    //根据名字从bean工厂获取bean
    Hello hello = (Hello) bf.getBean("hello");
    hello.sayHello();

    Hello2 hello2 = (Hello2) bf.getBean("hello2");
    hello2.sayHello();

}

protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws IOException {
    XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

    String[] configLocations = new String[] { "beans2.xml" };
    if (configLocations != null) {
        beanDefinitionReader.loadBeanDefinitions(configLocations);
    }
}

protected Object doGetBean(
            final String name, final Class requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException {

    final String beanName = transformedBeanName(name);
    Object bean = null;

    // 解决set循环依赖
    Object sharedInstance = getSingleton(beanName);
    if (sharedInstance != null && args == null) {
        ...
    }

    else {
        ...
        // 创建单件bean.
        if (mbd.isSingleton()) {
            sharedInstance = getSingleton(beanName, new ObjectFactory() {
                public Object getObject() throws BeansException {
                    try {
                        return createBean(beanName, mbd, args);
                    }
                    catch (BeansException ex) {
                    ...
                        throw ex;
                    }
                }
            });
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
        }
       //创建原型bean
        else if (mbd.isPrototype()) {
            ...
        }
        //创建request作用域bean
        else {
            ...
        }
    }
            ...
    return bean;
}

public Object getSingleton(String beanName, ObjectFactory singletonFactory) {
    Assert.notNull(beanName, "'beanName' must not be null");
    synchronized (this.singletonObjects) {
        Object singletonObject = this.singletonObjects.get(beanName);
        if (singletonObject == null) {
            ...
            beforeSingletonCreation(beanName);
            ...
            try {
                singletonObject = singletonFactory.getObject();
            }
            catch (BeanCreationException ex) {
                ...
            }
            finally {
                if (recordSuppressedExceptions) {
                    this.suppressedExceptions = null;
                }
                afterSingletonCreation(beanName);
            }
            addSingleton(beanName, singletonObject);
        }
        return (singletonObject != NULL_OBJECT ? singletonObject : null);
    }
}

protected void addSingleton(String beanName, Object singletonObject) {
    synchronized (this.singletonObjects) {
        this.singletonObjects.put(beanName, (singletonObject != null ? singletonObject : NULL_OBJECT));
        this.singletonFactories.remove(beanName);
        this.earlySingletonObjects.remove(beanName);
        this.registeredSingletons.add(beanName);
    }
}

private final Map singletonObjects = CollectionFactory.createConcurrentMapIfPossible(16);

    <bean id="hello" class="com.zlx.demo.Hello" scope="prototype"/>

protected <T> T doGetBean(
        final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
        throws BeansException {

    final String beanName = transformedBeanName(name);
    Object bean;

    // Eagerly check singleton cache for manually registered singletons.
    Object sharedInstance = getSingleton(beanName);
    if (sharedInstance != null && args == null) {
     ...
    }

    else {
        ...

        try {
            ...

            // Create bean instance.
            if (mbd.isSingleton()) {
                ...
            }
            //创建原型bean
            else if (mbd.isPrototype()) {
                // It's a prototype -> create a new instance.
                Object prototypeInstance = null;
                try {
                    beforePrototypeCreation(beanName);
                    prototypeInstance = createBean(beanName, mbd, args);
                }
                finally {
                    afterPrototypeCreation(beanName);
                }
                bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
            }

            else {
                ...
            }
        }
        catch (BeansException ex) {
            cleanupAfterBeanCreationFailure(beanName);
            throw ex;
        }
    }
 ...
    return (T) bean;
}

    public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {

        //如果XML打开了优化开关，或者设置为了代理目标类，或者目前类没有接口
        if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {
            Class<?> targetClass = config.getTargetClass();
            if (targetClass == null) {
                throw new AopConfigException("TargetSource cannot determine target class: " +
                        "Either an interface or a target is required for proxy creation.");
            }

            //如果有接口，或者通过Proxy.newProxyInstance生成的，则使用jdk动态代理
            if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
                return new JdkDynamicAopProxy(config);
            }

            //使用cglib
            return new ObjenesisCglibAopProxy(config);
        }
        else {
            //使用jdk动态代理
            return new JdkDynamicAopProxy(config);
        }
    }

class ScopedProxyBeanDefinitionDecorator implements BeanDefinitionDecorator {

    private static final String PROXY_TARGET_CLASS = "proxy-target-class";

    @Override
    public BeanDefinitionHolder decorate(Node node, BeanDefinitionHolder definition, ParserContext parserContext) {
        boolean proxyTargetClass = true;
        if (node instanceof Element) {
            Element ele = (Element) node;
            if (ele.hasAttribute(PROXY_TARGET_CLASS)) {
                proxyTargetClass = Boolean.valueOf(ele.getAttribute(PROXY_TARGET_CLASS));
            }
        }

        // 创建scoped的代理类，并注册到容器
        BeanDefinitionHolder holder =
                ScopedProxyUtils.createScopedProxy(definition, parserContext.getRegistry(), proxyTargetClass);
        String targetBeanName = ScopedProxyUtils.getTargetBeanName(definition.getBeanName());
        parserContext.getReaderContext().fireComponentRegistered(
                new BeanComponentDefinition(definition.getBeanDefinition(), targetBeanName));
        return holder;
    }

}

  <bean id="lavaPvgInfo" class="com.alibaba.lava.privilege.PrivilegeInfo"
        scope="request">
        <property name="aesKey" value="666" />
        <aop:scoped-proxy />
    </bean>

public MethodInterceptor[] getInterceptors(Advisor advisor) throws UnknownAdviceTypeException {
    List<MethodInterceptor> interceptors = new ArrayList<MethodInterceptor>(3);

    //从advistor中获取advice
    Advice advice = advisor.getAdvice();

    //如果实现了MethodInterceptor则直接加入，比如AspectJAroundAdvice，AspectJAfterAdvice
    if (advice instanceof MethodInterceptor) {
        interceptors.add((MethodInterceptor) advice);
    }

    //否者看是否有当前advice的适配器，首先检验是否支持，支持则返回对应的适配器
    for (AdvisorAdapter adapter : this.adapters) {
        if (adapter.supportsAdvice(advice)) {
            interceptors.add(adapter.getInterceptor(advisor));
        }
    }
    if (interceptors.isEmpty()) {
        throw new UnknownAdviceTypeException(advisor.getAdvice());
    }
    return interceptors.toArray(new MethodInterceptor[interceptors.size()]);
}

class MethodBeforeAdviceAdapter implements AdvisorAdapter, Serializable {

    public boolean supportsAdvice(Advice advice) {
        return (advice instanceof MethodBeforeAdvice);
    }

    public MethodInterceptor getInterceptor(Advisor advisor) {
        MethodBeforeAdvice advice = (MethodBeforeAdvice) advisor.getAdvice();
        return new MethodBeforeAdviceInterceptor(advice);
    }

}

public class MethodBeforeAdviceInterceptor implements MethodInterceptor, Serializable {

    private MethodBeforeAdvice advice;

    /**
     * Create a new MethodBeforeAdviceInterceptor for the given advice.
     * @param advice the MethodBeforeAdvice to wrap
     */
    public MethodBeforeAdviceInterceptor(MethodBeforeAdvice advice) {
        Assert.notNull(advice, "Advice must not be null");
        this.advice = advice;
    }

    public Object invoke(MethodInvocation mi) throws Throwable {
        this.advice.before(mi.getMethod(), mi.getArguments(), mi.getThis() );
        return mi.proceed();
    }

}