RequestMapping注解方式的handler

约定不等于承诺〃 2022-12-12 15:18 179阅读 0赞

## 1：@XXXMapping ##

为了是实现通过方法定义handler，springmvc定义了如下的一些注解：

org.springframework.web.servlet.bind.annotation.@RequestMapping
    org.springframework.web.servlet.bind.annotation.@GetMapping
    org.springframework.web.servlet.bind.annotation.@PostMapping
    org.springframework.web.servlet.bind.annotation.@PutMapping
    org.springframework.web.servlet.bind.annotation.@DeleteMapping
    org.springframework.web.servlet.bind.annotation.@PatchMapping

我们知道每种handler都需要有对应的HandlerMapping来管理`requestPath->Handler`的对应关系，对于这类注解`这个HandlerMapping就是RequestMappingHandlerMapping`,其UML图如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center]  
作为例子，看下以下定义的handler在程序中`最终获取的Handler是什么样子的`：

我们可以通过`org.springframework.web.servlet.handler.AbstractHandlerMapping#getHanlder`方法中调用模板方法的获取的Handler的信息：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 1]  
可以看到该handler的类型是`org.springframework.web.method.HandlerMethod`类型的，该类型是为了专门用来在封装`作为handler方法`,当然，本例就属于这种情况。

## 2：初始化入口 ##

获取的工作是由`org.springframework.web.mvc.annotation.RequstMappingHandlerMapping`类完成的，其中方法的入口是在其父类`org.springframework.web.servlet.handler.AbstractHandlerMethodMapping`中，该类因为实现了`org.springframework.beans.factory,InitializingBean`接口，因此spring容器在初始化时会在`属性设置完毕后`调用其`afterPropertiesSet()`方法，但是最开始的入口并不是这里，而是在`org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping#afterPropertiesSet`源码如下：

org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping#afterPropertiesSet
    @Override
    public void afterPropertiesSet() { 
    	this.config = new RequestMappingInfo.BuilderConfiguration();
    	this.config.setUrlPathHelper(getUrlPathHelper());
    	this.config.setPathMatcher(getPathMatcher());
    	this.config.setSuffixPatternMatch(this.useSuffixPatternMatch);
    	this.config.setTrailingSlashMatch(this.useTrailingSlashMatch);
    	this.config.setRegisteredSuffixPatternMatch(this.useRegisteredSuffixPatternMatch);
    	this.config.setContentNegotiationManager(getContentNegotiationManager());
    
    	super.afterPropertiesSet();
    }

注意代码`super.afterPropertiesSet();`就会调用`org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#afterPropertiesSet`完成相关HandlerMethod的初始化。

## 3：AbstractHandlerMethodMapping\#initHandlerMethods ##

### 3.1：测试使用的controller ###

我们以如下的controller来进行说明：

@Controller
    @RequestMapping("/testinterceptor")
    public class TestinterceptorController { 
    
    	@RequestMapping("/hi")
    	@ResponseBody
    	public String hi() { 
    		String msg = "testinterceptor hi";
    		System.out.println(msg);
    		return msg;
    	}
    
    	@GetMapping("/hey")
    	@ResponseBody
    	public String hey() { 
    		String msg = "testinterceptor hey";
    		System.out.println(msg);
    		return msg;
    	}
    }

### 3.2：initHandlerMethods ###

方法：

protected void initHandlerMethods() { 
    	for (String beanName : getCandidateBeanNames()) { 
    		if (!beanName.startsWith(SCOPED_TARGET_NAME_PREFIX)) { 
    			processCandidateBean(beanName);
    		}
    	}
    	handlerMethodsInitialized(getHandlerMethods());
    }

这里循环所有的bean名称来进行处理，为了方便我们的调试，增加`"testinterceptorController".equalsIgnoreCase(beanName)`的条件变量：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 2]

循环内部是通过方法`processCandidateBean`来处理的，接下来看这个方法。

### 3.3：processCandidateBean ###

源码：

protected void processCandidateBean(String beanName) { 
    		Class<?> beanType = null;
    		try { 
    			// <1>
    			beanType = obtainApplicationContext().getType(beanName);
    		}
    		catch (Throwable ex) { 
    			// An unresolvable bean type, probably from a lazy bean - let's ignore it.
    			if (logger.isTraceEnabled()) { 
    				logger.trace("Could not resolve type for bean '" + beanName + "'", ex);
    			}
    		}
    		// <2>
    		if (beanType != null && isHandler(beanType)) { 
    			// <3>
    			detectHandlerMethods(beanName);
    		}
    }

`<1>`处代码是获取bean的类型，这里debug如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 3]  
`<2>`处代码是判断当前的bean是否是一个handler，在AbstractHandlerMethodMapping中定义的是抽象方法`protected abstract boolean isHandler(Class<?> beanType);`其具体实现是在RequestMappingHandlerMapping中，源码如下：

@Override
    protected boolean isHandler(Class<?> beanType) { 
    	return (AnnotatedElementUtils.hasAnnotation(beanType, Controller.class) ||
    			AnnotatedElementUtils.hasAnnotation(beanType, RequestMapping.class));
    }

就是判断是否有`@Controller`注解或者是`@RequestMapping`注解，很明显，我们这里是满足要求的。因此会继续执行`<3>`处代码。  
3.4：detectHandlerMethods(beanName)  
源码：

protected void detectHandlerMethods(Object handler) { 
        // <1>
    	Class<?> handlerType = (handler instanceof String ?
    			obtainApplicationContext().getType((String) handler) : handler.getClass());
    
    	if (handlerType != null) { 
    		Class<?> userType = ClassUtils.getUserClass(handlerType);
    		// <2>
    		Map<Method, T> methods = MethodIntrospector.selectMethods(userType,
    				(MethodIntrospector.MetadataLookup<T>) method -> { 
    					try { 
    						return getMappingForMethod(method, userType);
    					}
    					catch (Throwable ex) { 
    						throw new IllegalStateException("Invalid mapping on handler class [" +
    								userType.getName() + "]: " + method, ex);
    					}
    				});
    		if (logger.isTraceEnabled()) { 
    			logger.trace(formatMappings(userType, methods));
    		}
    		// <3>
    		methods.forEach((method, mapping) -> { 
    			Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
    			registerHandlerMethod(handler, invocableMethod, mapping);
    		});
    	}
    }

`<1>`处代码是获取类型，变量`handler`一般是String类型的，其实就是bean名称，所以会通过容器获取类型，`<2>`处是获取定义的所有方法，例如如下的定义，

@Controller
    @RequestMapping("/testinterceptor")
    public class TestinterceptorController { 
    
    	@RequestMapping("/hi")
    	@ResponseBody
    	public String hi(String hiName, String hiAge) { 
    		String msg = "testinterceptor hi";
    		System.out.println(msg);
    		return msg;
    	}
    
    	@GetMapping("/hey")
    	@ResponseBody
    	public String hey(String heyName, String heyAge) { 
    		String msg = "testinterceptor hey";
    		System.out.println(msg);
    		return msg;
    	}
    }

`<1>`和`<2>`debug信息:  
![在这里插入图片描述][20201010151448168.jpg_pic_center]  
`<3>`处的循环所有方法并进行注册，接下来看下方法registerHandlerMethod是如何完成方法注册的。

### 3.4：registerHandlerMethod ###

源码：

protected void registerHandlerMethod(Object handler, Method method, T mapping) { 
    	this.mappingRegistry.register(mapping, handler, method);
    }

直接调用`org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.MappingRegistry#register方法`,源码：

public void register(T mapping, Object handler, Method method) { 
    	this.readWriteLock.writeLock().lock();
    	try { 
    	    // <1>
    		HandlerMethod handlerMethod = createHandlerMethod(handler, method);
    		// <2>
    		assertUniqueMethodMapping(handlerMethod, mapping);
    		// <3>
    		this.mappingLookup.put(mapping, handlerMethod);
    		// <4>
    		List<String> directUrls = getDirectUrls(mapping);
    		// <5>
    		for (String url : directUrls) { 
    			this.urlLookup.add(url, mapping);
    		}
    		// <6>
    		String name = null;
    		if (getNamingStrategy() != null) { 
    			name = getNamingStrategy().getName(handlerMethod, mapping);
    			addMappingName(name, handlerMethod);
    		}
    
    		CorsConfiguration corsConfig = initCorsConfiguration(handler, method, mapping);
    		if (corsConfig != null) { 
    			this.corsLookup.put(handlerMethod, corsConfig);
    		}
    		// <7>
    		this.registry.put(mapping, new MappingRegistration<>(mapping, handlerMethod, directUrls, name));
    	}
    	finally { 
    		this.readWriteLock.writeLock().unlock();
    	}
    }

`<1>`处代码生成HandlerMethod对象，单起一部分讲解，`<2>`是保证完全相同的`@RequestMapping`只存在一个，源码如下：

private void assertUniqueMethodMapping(HandlerMethod newHandlerMethod, T mapping) {
    	HandlerMethod handlerMethod = this.mappingLookup.get(mapping);
    	if (handlerMethod != null && !handlerMethod.equals(newHandlerMethod)) {
    		throw new IllegalStateException(
    				"Ambiguous mapping. Cannot map '" +	newHandlerMethod.getBean() + "' method \n" +
    				newHandlerMethod + "\nto " + mapping + ": There is already '" +
    				handlerMethod.getBean() + "' bean method\n" + handlerMethod + " mapped.");
    	}
    }

其中异常中的信息在开发过程中应该是经常见到的`（毕竟ctrlc，ctrlv比较多！！！）`,另外这里需要注意这里冲突的mapping其实并不是一个对象，因为每次都是重新生成的新对象，但是RequestMappingInfo重写了hashCode和equals方法，这样在get的时候信息完全相同的就认为是相同的key，其中源码如下：

org.springframework.web.servlet.mvc.method.RequestMappingInfo#hashCode
    @Override
    public int hashCode() { 
    	return (this.patternsCondition.hashCode() * 31 +  // primary differentiation
    			this.methodsCondition.hashCode() + this.paramsCondition.hashCode() +
    			this.headersCondition.hashCode() + this.consumesCondition.hashCode() +
    			this.producesCondition.hashCode() + this.customConditionHolder.hashCode());
    }
    
    org.springframework.web.servlet.mvc.method.RequestMappingInfo#equals
    @Override
    public boolean equals(Object other) { 
    	if (this == other) { 
    		return true;
    	}
    	if (!(other instanceof RequestMappingInfo)) { 
    		return false;
    	}
    	RequestMappingInfo otherInfo = (RequestMappingInfo) other;
    	return (this.patternsCondition.equals(otherInfo.patternsCondition) &&
    			this.methodsCondition.equals(otherInfo.methodsCondition) &&
    			this.paramsCondition.equals(otherInfo.paramsCondition) &&
    			this.headersCondition.equals(otherInfo.headersCondition) &&
    			this.consumesCondition.equals(otherInfo.consumesCondition) &&
    			this.producesCondition.equals(otherInfo.producesCondition) &&
    			this.customConditionHolder.equals(otherInfo.customConditionHolder));
    }

`<3>`处存储Mapping和HandlerMethod的对应关系，其实就是`@RequestMapping信息和所在方法的对应关系`。`<4>`获取Mapping中的url，需要注意，这里的URL必须是`直接URL,即直接确定的URL`，如`hi/{id}`，`hey/*`就不是直接URL,如`hi/hey`就是直接URL，如下的定义：

@RequestMapping(value = { "multi_url_1", "multi_url_2", "multi_url_3" }, method = RequestMethod.GET)
    @ResponseBody
    public String multiValue(){}

该值debug如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 4]  
`<5>`处代码存储`url->mapping的对应关系`，urlLookUp的定义是`MultiValueMap<String, T> urlLookup = new LinkedMultiValueMap<>();`因为相同的url可能存在不通过的mapping，所以这里使用的是MultiValueMap，比如如下就是这种情况：

@RequestMapping(value = "/url_1", method = RequestMethod.GET)
    @ResponseBody
    public String url_1(){}
    @RequestMapping(value = "/url_1", method = RequestMethod.POST)
    @ResponseBody
    public String url_2(){}

在`@RequestMapping`中只有method不一样，url都是`url_1`，但也是不同的RequestMappingInfo。`<6>`处代码生成mapping的名称，然后保存其对应的HandlerMethod，其中nameLookUp定义是`Map<String, List<HandlerMethod>> nameLookup = new ConcurrentHashMap<>();`，不同的handlermethod对应的Maping的名字可能是一样的，所以这样存储，这和mapping名称的生成策略有关系，策略为`类简单名称大写字符拼接+#+方法名`，源码：

org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMethodMappingNamingStrategy#getName
    public String getName(HandlerMethod handlerMethod, RequestMappingInfo mapping) { 
    	if (mapping.getName() != null) { 
    		return mapping.getName();
    	}
    	StringBuilder sb = new StringBuilder();
    	String simpleTypeName = handlerMethod.getBeanType().getSimpleName();
    	for (int i = 0; i < simpleTypeName.length(); i++) { 
    		if (Character.isUpperCase(simpleTypeName.charAt(i))) { 
    			sb.append(simpleTypeName.charAt(i));
    		}
    	}
    	sb.append(SEPARATOR).append(handlerMethod.getMethod().getName());
    	return sb.toString();
    }

比如某个controller叫做MotherFuckerController,方法名称hi，另一个controller叫做是MoonFineController，同样有方法hi，则生成的名字就是重复的了,结果都是`MFC#hi`。`<7>`处用`mapping+handlermethod+directUrls+name`定义MappingRegistration并以mapping为key存放。接下来继续看生成HandlerMethod的`createHandlerMethod`方法。

### 3.5：createHandlerMethod ###

protected HandlerMethod createHandlerMethod(Object handler, Method method) { 
    		HandlerMethod handlerMethod;
    	if (handler instanceof String) { 
    		String beanName = (String) handler;
    		// <1>
    		handlerMethod = new HandlerMethod(beanName,
    				obtainApplicationContext().getAutowireCapableBeanFactory(), method);
    	}
    	else { 
    		handlerMethod = new HandlerMethod(handler, method);
    	}
    	return handlerMethod;
    }

主要看`<1>`处代码，源码如下：

public HandlerMethod(String beanName, BeanFactory beanFactory, Method method) { 
    	Assert.hasText(beanName, "Bean name is required");
    	Assert.notNull(beanFactory, "BeanFactory is required");
    	Assert.notNull(method, "Method is required");
    	this.bean = beanName;
    	this.beanFactory = beanFactory;
    	Class<?> beanType = beanFactory.getType(beanName);
    	if (beanType == null) { 
    		throw new IllegalStateException("Cannot resolve bean type for bean with name '" + beanName + "'");
    	}
    	// <HandlerMethod_1>
    	this.beanType = ClassUtils.getUserClass(beanType);
    	this.method = method;
    	// <HandlerMethod_2>
    	this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
    	this.parameters = initMethodParameters();
    	// <HandlerMethod_3>
    	evaluateResponseStatus();
    }

`<HandlerMethod_1>`处代码处理如果是代理类时获取其原始类型。`<HandlerMethod_2>`处代码是如果该方法是桥接方法则获取其原始方法。`<HandlerMethod_3>`处代码是处理使用了`@ResponseStatus`的情况。

## 4：请求时获取HandlerMethod ##

请求的入口自然是在`org.springframework.web.servlet.DispatcherServlet#doDispatch`中的如下代码调用,对这里有疑问的朋友可以参考[一次GET请求在springmvc中是的处理流程][GET_springmvc]:

mappedHandler = getHandler(processedRequest);

getHandler源码：

protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { 
    	if (this.handlerMappings != null) { 
    		for (HandlerMapping mapping : this.handlerMappings) { 
    			HandlerExecutionChain handler = mapping.getHandler(request);
    			if (handler != null) { 
    				return handler;
    			}
    		}
    	}
    	return null;
    }

其中我们这里因为使用的是`@XXXMapping`的方式，所以这里的mapping就是`RequestHandlerMapping`，而getHandler方法是在[AbstractHandlerMapping][]中定义的，源码如下：

public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
    	// 获取request对应的handler
    	Object handler = getHandlerInternal(request);
    	if (handler == null) {
    		handler = getDefaultHandler();
    	}
    	if (handler == null) {
    		return null;
    	}
    	// Bean name or resolved handler?
    	// 如果是查询到的handler是String，则从容器中获取对应名称的handler对象
    	if (handler instanceof String) {
    		String handlerName = (String) handler;
    		handler = obtainApplicationContext().getBean(handlerName);
    	}
    	// 获取符合请求的HandlerInterceptor并设置到
    	HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
    
    	if (logger.isTraceEnabled()) {
    		logger.trace("Mapped to " + handler);
    	}
    	else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
    		logger.debug("Mapped to " + executionChain.getHandler());
    	}
    
    	if (CorsUtils.isCorsRequest(request)) {
    		CorsConfiguration globalConfig = this.corsConfigurationSource.getCorsConfiguration(request);
    		CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
    		CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
    		executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
    	}
    
    	return executionChain;
    }

主要看方法`Object handler = getHandlerInternal(request);`该模板方法实现是在`org.springframework.web.servlet.handler.AbstractHandlerMethodMapping`中，那么就让我们从这里开始吧！

### 4.1：AbstractHandlerMethodMapping\#getHandlerInternal ###

源码：

protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception { 
        // <1>
    	String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
    	this.mappingRegistry.acquireReadLock();
    	try { 
    		// <2>
    		HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
    		// <3>
    		return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
    	}
    	finally { 
    		this.mappingRegistry.releaseReadLock();
    	}
    }

`<1>`处代码获取请求路径，如`http://localhost:8080/testinterceptor/consume_and_produce?myParam=myValue`，lookupPaht为`/testinterceptor/consume_and_produce`,`<2>`处代码为获取HandlerMethod的核心方法，单独分析，`<3>`处代码如果HandlerMethod所属的bean还没有获取，则获取，并重新创建HandlerMethod对象，源码如下：

public HandlerMethod createWithResolvedBean() { 
    	Object handler = this.bean;
    	if (this.bean instanceof String) { 
    		Assert.state(this.beanFactory != null, "Cannot resolve bean name without BeanFactory");
    		String beanName = (String) this.bean;
    		handler = this.beanFactory.getBean(beanName);
    	}
    	return new HandlerMethod(this, handler);
    }

### 4.2：AbstractHandlerMethodMapping\#lookupHandlerMethod ###

源码：

protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception { 
    	// <1>
    	List<Match> matches = new ArrayList<>();
    	// <2>
    	List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
    	if (directPathMatches != null) { 
    		// <3>
    		addMatchingMappings(directPathMatches, matches, request);
    	}
    	// <4>
    	if (matches.isEmpty()) { 
    		// No choice but to go through all mappings...
    		addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
    	}
    	
    	if (!matches.isEmpty()) { 
    		// <5>
    		Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
    		// <6>
    		matches.sort(comparator);
    		// <7>
    		Match bestMatch = matches.get(0);
    		// <8>
    		if (matches.size() > 1) { 
    			if (logger.isTraceEnabled()) { 
    				logger.trace(matches.size() + " matching mappings: " + matches);
    			}
    			if (CorsUtils.isPreFlightRequest(request)) { 
    				return PREFLIGHT_AMBIGUOUS_MATCH;
    			}
    			Match secondBestMatch = matches.get(1);
    			// <9>
    			if (comparator.compare(bestMatch, secondBestMatch) == 0) { 
    				Method m1 = bestMatch.handlerMethod.getMethod();
    				Method m2 = secondBestMatch.handlerMethod.getMethod();
    				String uri = request.getRequestURI();
    				throw new IllegalStateException(
    						"Ambiguous handler methods mapped for '" + uri + "': {" + m1 + ", " + m2 + "}");
    			}
    		}
    		// <10>
    		request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.handlerMethod);
    		// <11>
    		handleMatch(bestMatch.mapping, lookupPath, request);
    		// <12>
    		return bestMatch.handlerMethod;
    	}
    	else { 
    	    // <13>
    		return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
    	}
    }

`<1>`处的Match是`Mpping+HanlderMethod`的封装对象，源码如下：

private class Match { 
        // Mappping, 如果是RequestMappingInfoHandlerMapping，则是RequestMappingInfo
        // public abstract class RequestMappingInfoHandlerMapping extends AbstractHandlerMethodMapping<RequestMappingInfo>
    	private final T mapping;
    	// HanlderMethod, 如@RequestMapping注解修饰方法+bean信息组合
    	private final HandlerMethod handlerMethod;
    	...snip...
    }

该集合就是用于封装匹配的mapping即其对应的方法信息的，`<2>`处代码是根据请求路径获取Mapping信息`（注意此时的mapping仅仅只是满足路径匹配要去的，其它要求不一定满足，如method，consumes，produces，params，heanders等）`，`<3>`处通过请求方法，头信息，参数等进一步过滤mapping。`<4>`处如果是没有匹配的，则通过遍历的方式再筛一遍`（无奈之举,其实我觉得意义不大，所以老外写的注释是：No choice but to go through all mappings...）`。`<5>`处是创建`MatchComparator`，其实现了`java.util.Comparator`接口，然后通过`<6>`按照Mapping的匹配程度进行排序，匹配程度从高到低进行排序，`<7>`处是获取第一个元素，其就是最匹配元素，`<8>`处是处理最匹配和次匹配Mapping完全相同的情况`（当@RequestMapping信息完全相同的时候）`，例如下面这种就会出现这种问题：

@RequestMapping(value = { "/common_requestmapping"})
    @RequestMapping(value = { "/common_requestmapping", "xxx"})

使用请求`http://localhost:8080/testinterceptor/common_requestmapping`，访问如下图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 5]  
以上的异常其实就是通过`<9>`处的代码产生的，虽然第二个提供了多个value，但是这种是不影响mapping的优先级的，还有如果是虽然存在相同优先级的，但是不是最匹配和次匹配重复，也是可以的，如下映射：

@RequestMapping(value = { "/common_requestmapping"},method = RequestMethod.GET)--最匹配
    @RequestMapping(value = { "/common_requestmapping", "xxx"})
    @RequestMapping(value = { "/common_requestmapping", "yyy"})

访问`http://localhost:8080/testinterceptor/common_requestmapping`：  
![在这里插入图片描述][20201015102816473.jpg_pic_center]  
`<9>`就是比较最高优先级和次高优先级是否相同，如果是相同的话，则无法确定使用哪一个，直接抛出异常`java.lang.IllegalStateException`的运行时异常。`<10>,<11>`,都是往requst中设置一些属性。`<12>`返回最匹配的HandlerMethod。`<13>`代码是处理无法正常访问的原因的，比如其它都是匹配的，但是请求方法不匹配，如`@RequestMapping(value = {"/error_method"}, method = RequestMethod.GET)`如果如下使用post方式访问，则会返回`405 Method Not Allowed`错误，如下图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 6]

## 最后：都让开，我要喝瑞幸 ##

![在这里插入图片描述][20200828090303329.png_pic_center]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 2]: /images/20221123/7ee3d0eef56b4cb883a163f3694f03d0.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 3]: /images/20221123/70ff61fccc6145e7aa0df6f6221bf1d2.png
[20201010151448168.jpg_pic_center]: /images/20221123/41561c384e1046b3ad8f40ba41c0820f.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 4]: /images/20221123/a7d8f82836f641049d8cf1ae5b3f17a6.png
[GET_springmvc]: https://blog.csdn.net/wang0907/article/details/108917070
[AbstractHandlerMapping]: https://blog.csdn.net/wang0907/article/details/108925784
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 5]: /images/20221123/8846e4d06a6d4b43bfe520c53833d239.png
[20201015102816473.jpg_pic_center]: /images/20221123/d42ef46f17934928bd467090224baa3e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dhbmcwOTA3_size_16_color_FFFFFF_t_70_pic_center 6]: /images/20221123/491bb1f3969b4563814bf42e05e5f37b.png
[20200828090303329.png_pic_center]: /images/20221123/2268f590ecb94a05b47787ea1762da63.png