spring5.1.x源码解析之十二(列出10大设计模式)

桃扇骨 2023-05-21 07:17 9阅读 0赞

### 文章目录 ###

*   *  责任链模式
     *  工厂模式
     *  装饰者模式
     *  策略模式
     *  模板设计模式
     *  适配器设计模式
     *  观察者模式
     *  原型模式
     *  代理模式
     *  单例模式

## 责任链模式 ##

org.springframework.aop.framework.CglibAopProxy.DynamicAdvisedInterceptor\#intercept

public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
        
    		
    		...
    		retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();
    		...
    		}

public Object proceed() throws Throwable {
        
    ...
    			//将this作为参数传递,保证当前实例中调用链的执行
    	interceptorOrInterceptionAdvice).invoke(this);
    	...
    	}

## 工厂模式 ##

org.springframework.beans.factory.support.AbstractBeanFactory\#doGetBean

protected <T> T doGetBean(final String name, @Nullable final Class<T> requiredType,
    							  @Nullable final Object[] args, boolean typeCheckOnly) throws BeansException {
        
    ...
    	sharedInstance = getSingleton(beanName, () -> {
        
    						try {
        
    							return createBean(beanName, mbd, args);
    						} catch (BeansException ex) {
        
    							// Explicitly remove instance from singleton cache: It might have been put there
    							// eagerly by the creation process, to allow for circular reference resolution.
    							// Also remove any beans that received a temporary reference to the bean.
    							destroySingleton(beanName);
    							throw ex;
    						}
    					});
    ...
    	}

## 装饰者模式 ##

org.springframework.beans.factory.xml.XmlBeanDefinitionReader\#loadBeanDefinitions(org.springframework.core.io.Resource)

@Override
    	public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
        
    		return loadBeanDefinitions(new EncodedResource(resource));
    	}

## 策略模式 ##

针对不同Resource有不同的实现,从而使用不同的Factory解析  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L051YW5fRmVuZw_size_16_color_FFFFFF_t_70]

## 模板设计模式 ##

声明一个抽象方法,使方法的调用延迟到子类初始化  
org.springframework.dao.support.DaoSupport\#afterPropertiesSet

public final void afterPropertiesSet() throws IllegalArgumentException, BeanInitializationException {
        
    		// Let abstract subclasses check their configuration.
    		//模板设计模式,主要子类实现
    		checkDaoConfig();
    
    		// Let concrete implementations initialize themselves.
    		try {
        
    			//对dao初始化
    			initDao();
    		}
    		catch (Exception ex) {
        
    			throw new BeanInitializationException("Initialization of DAO failed", ex);
    		}
    	}

## 适配器设计模式 ##

org.springframework.web.servlet.DispatcherServlet\#initStrategies

protected void initStrategies(ApplicationContext context) {
        
    		//处理文件上传,如果想使用multipart,则需要添加对应解析器
    		initMultipartResolver(context);
    		//国际化,分别支持url,session,cookie三种配置
    		initLocaleResolver(context);
    		//theme主题控制页面风格,
    		initThemeResolver(context);
    		//处理映射器:Controller映射处理,可设置多个,分别根据优先级处理
    		initHandlerMappings(context);
    		//适配器,通过处理映射器得到处理,轮询适配器,查找能够处理当前HTTP请求的,从而适配当前HTTP请求
    		//适配器设计模式
    		initHandlerAdapters(context);
    		//异常处理器,返回一个ModelAndView
    		initHandlerExceptionResolvers(context);
    		//当Controller没有返回视图,response没有流,则通过实现了此接口的类来确定此种情况下返回viewName的约定
    					//支持前后缀等
    		initRequestToViewNameTranslator(context);
    		//选择view渲染
    		initViewResolvers(context);
    		//请求存储
    			//场景,重定向的时候,定向后依旧能使用定向前数据
    		initFlashMapManager(context);
    	}

## 观察者模式 ##

org.springframework.beans.factory.parsing.ReaderContext的eventListener对象,监控每次情况

public void fireDefaultsRegistered(DefaultsDefinition defaultsDefinition) {
        
    		this.eventListener.defaultsRegistered(defaultsDefinition);
    	}
    
    	/**
    	 * Fire an component-registered event.
    	 */
    	public void fireComponentRegistered(ComponentDefinition componentDefinition) {
        
    		this.eventListener.componentRegistered(componentDefinition);
    	}
    
    	/**
    	 * Fire an alias-registered event.
    	 */
    	public void fireAliasRegistered(String beanName, String alias, @Nullable Object source) {
        
    		this.eventListener.aliasRegistered(new AliasDefinition(beanName, alias, source));
    	}

调用  
org.springframework.beans.factory.xml.DefaultBeanDefinitionDocumentReader\#processBeanDefinition

protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
        
    		//dbHolder包含配置文件中配置的各种属性,如class,name,id之类的属性
    		BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
    		if (bdHolder != null) {
        
    			//若存在默认标签的子节点下再有自定义属性,则再次对自定义标签解析
    			bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
    			try {
        
    				// Register the final decorated instance.
    				//对解析后的dbHolder进行注册
    				BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
    			}
    			catch (BeanDefinitionStoreException ex) {
        
    				getReaderContext().error("Failed to register bean definition with name '" +
    						bdHolder.getBeanName() + "'", ele, ex);
    			}
    			// Send registration event.
    			//发出响应事件,通知相关监听器，这个bean已经加载完成
    			getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
    		}
    	}

## 原型模式 ##

protected RootBeanDefinition getMergedBeanDefinition(
    			String beanName, BeanDefinition bd, @Nullable BeanDefinition containingBd)
    			throws BeanDefinitionStoreException {
        
    	...
    	//原型模式
    						mbd = ((RootBeanDefinition) bd).cloneBeanDefinition();
    	...
    	}

@Override
    	public RootBeanDefinition cloneBeanDefinition() {
        
    		return new RootBeanDefinition(this);
    	}
    
    	public RootBeanDefinition(RootBeanDefinition original) {
        
    		super(original);
    		this.decoratedDefinition = original.decoratedDefinition;
    		this.qualifiedElement = original.qualifiedElement;
    		this.allowCaching = original.allowCaching;
    		this.isFactoryMethodUnique = original.isFactoryMethodUnique;
    		this.targetType = original.targetType;
    	}

## 代理模式 ##

org.springframework.aop.framework.DefaultAopProxyFactory\#createAopProxy

public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
        
    		/*
    		optimize:只对cglib有效,控制cglib是否采用激进的优化策略
    		proxyTargetClass:true则表示cglib代理,而且表示目标类本身被代理而不是目标类的接口
    		hasNoUserSuppliedProxyInterfaces:是否存在代理接口
    		 */
    		//如果开启cglib激进策略,proxy-target-class=true(表示目标类本身被代理,采用cglib),存在代理接口
    		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.");
    			}
    			//如果代理类是接口,targetClass是代理类
    			if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
        
    				return new JdkDynamicAopProxy(config);
    			}
    			return new ObjenesisCglibAopProxy(config);
    		}
    		else {
        
    			return new JdkDynamicAopProxy(config);
    		}
    	}

## 单例模式 ##

就不讲了

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