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拦截器Interceptor的使用

自定义拦截器需要实现HandlerInterceptor接口。

package com.morris.spring.mvc.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyInterceptor implements HandlerInterceptor { 
   

    // 目标方法运行之前执行
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { 
   
        System.out.println("preHandle" + request.getRequestURI());
        return true;
    }

    // 目标方法运行之后执行
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception { 
   
        System.out.println("postHandle");
    }

    // 页面响应后执行
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception { 
   
        System.out.println("afterCompletion");
    }
}

配置拦截器以及要匹配的url：

com.morris.spring.mvc.config.MVCConfig#addInterceptors

// 添加拦截器
@Override
public void addInterceptors(InterceptorRegistry registry) { 
   
	registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**"); // /**拦截任意路径
	registry.addInterceptor(new LocaleChangeInterceptor()); // 不设置path就会拦截所有请求
}

源码分析

Interceptor的收集过程

RequestMappingHandlerMapping的实例化过程中，会完成所有的Interceptor的收集工作。

org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport#requestMappingHandlerMapping

@Bean
@SuppressWarnings("deprecation")
public RequestMappingHandlerMapping requestMappingHandlerMapping(
	@Qualifier("mvcContentNegotiationManager") ContentNegotiationManager contentNegotiationManager,
	@Qualifier("mvcConversionService") FormattingConversionService conversionService,
	@Qualifier("mvcResourceUrlProvider") ResourceUrlProvider resourceUrlProvider) { 
   

	RequestMappingHandlerMapping mapping = createRequestMappingHandlerMapping();
	mapping.setOrder(0);
	// 设置拦截器
	mapping.setInterceptors(getInterceptors(conversionService, resourceUrlProvider));
	mapping.setContentNegotiationManager(contentNegotiationManager);
	mapping.setCorsConfigurations(getCorsConfigurations());

	PathMatchConfigurer configurer = getPathMatchConfigurer();

	Boolean useSuffixPatternMatch = configurer.isUseSuffixPatternMatch();
	if (useSuffixPatternMatch != null) { 
   
		mapping.setUseSuffixPatternMatch(useSuffixPatternMatch);
	}
	Boolean useRegisteredSuffixPatternMatch = configurer.isUseRegisteredSuffixPatternMatch();
	if (useRegisteredSuffixPatternMatch != null) { 
   
		mapping.setUseRegisteredSuffixPatternMatch(useRegisteredSuffixPatternMatch);
	}
	Boolean useTrailingSlashMatch = configurer.isUseTrailingSlashMatch();
	if (useTrailingSlashMatch != null) { 
   
		mapping.setUseTrailingSlashMatch(useTrailingSlashMatch);
	}

	UrlPathHelper pathHelper = configurer.getUrlPathHelper();
	if (pathHelper != null) { 
   
		mapping.setUrlPathHelper(pathHelper);
	}
	PathMatcher pathMatcher = configurer.getPathMatcher();
	if (pathMatcher != null) { 
   
		mapping.setPathMatcher(pathMatcher);
	}
	Map<String, Predicate<Class<?>>> pathPrefixes = configurer.getPathPrefixes();
	if (pathPrefixes != null) { 
   
		mapping.setPathPrefixes(pathPrefixes);
	}

	return mapping;
}

org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport#getInterceptors

protected final Object[] getInterceptors(
	FormattingConversionService mvcConversionService,
	ResourceUrlProvider mvcResourceUrlProvider) { 
   
	if (this.interceptors == null) { 
   
		// interceptors默认为空
		InterceptorRegistry registry = new InterceptorRegistry();
		/** * @see DelegatingWebMvcConfiguration#addInterceptors(org.springframework.web.servlet.config.annotation.InterceptorRegistry) */
		addInterceptors(registry);
		// 添加两个默认的Interceptor
		registry.addInterceptor(new ConversionServiceExposingInterceptor(mvcConversionService));
		registry.addInterceptor(new ResourceUrlProviderExposingInterceptor(mvcResourceUrlProvider));
		this.interceptors = registry.getInterceptors();
	}
	return this.interceptors.toArray();
}

org.springframework.web.servlet.config.annotation.DelegatingWebMvcConfiguration#addInterceptors

protected void addInterceptors(InterceptorRegistry registry) { 
   
	this.configurers.addInterceptors(registry);
}

而MVCConfig实现了WebMvcConfigurer，最终会调到MVCConfig.addInterceptors()方法将我们自定义的Interceptor加入到RequestMappingHandlerMapping的interceptors属性中。

org.springframework.web.servlet.config.annotation.InterceptorRegistration#getInterceptor

protected Object getInterceptor() { 
   
	if (this.includePatterns.isEmpty() && this.excludePatterns.isEmpty()) { 
   
		return this.interceptor;
	}

	String[] include = StringUtils.toStringArray(this.includePatterns);
	String[] exclude = StringUtils.toStringArray(this.excludePatterns);
	// 包装为MappedInterceptor
	MappedInterceptor mappedInterceptor = new MappedInterceptor(include, exclude, this.interceptor);
	if (this.pathMatcher != null) { 
   
		mappedInterceptor.setPathMatcher(this.pathMatcher);
	}
	return mappedInterceptor;
}

org.springframework.web.servlet.handler.AbstractHandlerMapping#initApplicationContext

protected void initApplicationContext() throws BeansException { 
   
	extendInterceptors(this.interceptors);
	// 从spring mvc容器中获取所有的MappedInterceptor
	// 从这里可以看出，我们可以通过向spring mvc容器中注入MappedInterceptor来实现注入Interceptor
	detectMappedInterceptors(this.adaptedInterceptors);
	// 初始化interceptor
	// 将interceptors添加到adaptedInterceptors
	initInterceptors();
}

protected void initInterceptors() { 
   
	if (!this.interceptors.isEmpty()) { 
   
		for (int i = 0; i < this.interceptors.size(); i++) { 
   
			Object interceptor = this.interceptors.get(i);
			if (interceptor == null) { 
   
				throw new IllegalArgumentException("Entry number " + i + " in interceptors array is null");
			}
			this.adaptedInterceptors.add(adaptInterceptor(interceptor));
		}
	}
}

最后所有的Intercepor位于RequestMappingHandlerMapping的adaptedInterceptors属性。

Interceptor的执行过程

所有的请求都会经过DispatcherServlet的doDispatch()方法。

org.springframework.web.servlet.DispatcherServlet#doDispatch

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { 
   
	HttpServletRequest processedRequest = request;
	HandlerExecutionChain mappedHandler = null;
	boolean multipartRequestParsed = false;

	WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

	try { 
   
		ModelAndView mv = null;
		Exception dispatchException = null;

		try { 
   
			// 判断请求头中是否有文件，如果有会将请求包装为MultipartHttpServletRequest
			processedRequest = checkMultipart(request);
			multipartRequestParsed = (processedRequest != request);

			// Determine handler for the current request.
			// HandlerExecutionChain，获取Handler
			mappedHandler = getHandler(processedRequest);
			if (mappedHandler == null) { 
   
				noHandlerFound(processedRequest, response);
				return;
			}

			// Determine handler adapter for the current request.
			// 获取HandlerAdapter
			HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

			// Process last-modified header, if supported by the handler.
			String method = request.getMethod();
			boolean isGet = "GET".equals(method);
			if (isGet || "HEAD".equals(method)) { 
   
				long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
				if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) { 
   
					return;
				}
			}

			// 调用拦截器的HandlerInterceptor.preHandle()
			if (!mappedHandler.applyPreHandle(processedRequest, response)) { 
   
				return;
			}

			// Actually invoke the handler.
			/** * @see AbstractHandlerMethodAdapter#handle(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, java.lang.Object) */
			mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

			if (asyncManager.isConcurrentHandlingStarted()) { 
   
				return;
			}

			applyDefaultViewName(processedRequest, mv);
			// 调用拦截器的HandlerInterceptor.postHandle()
			mappedHandler.applyPostHandle(processedRequest, response, mv);
		}
		catch (Exception ex) { 
   
			dispatchException = ex;
		}
		catch (Throwable err) { 
   
			// As of 4.3, we're processing Errors thrown from handler methods as well,
			// making them available for @ExceptionHandler methods and other scenarios.
			dispatchException = new NestedServletException("Handler dispatch failed", err);
		}
		// 进行异常处理
		// 视图渲染
		// 调用拦截器的HandlerInterceptor.afterCompletion()
		processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
	}
	catch (Exception ex) { 
   
		// 调用拦截器的HandlerInterceptor.afterCompletion()
		triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
	}
	catch (Throwable err) { 
   
		// 调用拦截器的HandlerInterceptor.afterCompletion()
		triggerAfterCompletion(processedRequest, response, mappedHandler,
							   new NestedServletException("Handler processing failed", err));
	}
	finally { 
   
		if (asyncManager.isConcurrentHandlingStarted()) { 
   
			// Instead of postHandle and afterCompletion
			if (mappedHandler != null) { 
   
				mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
			}
		}
		else { 
   
			// Clean up any resources used by a multipart request.
			if (multipartRequestParsed) { 
   
				cleanupMultipart(processedRequest);
			}
		}
	}
}

将handler与interceptors封装为HandlerExecutionChain。

org.springframework.web.servlet.handler.AbstractHandlerMapping#getHandlerExecutionChain

protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) { 
   
	HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
								   (HandlerExecutionChain) handler : new HandlerExecutionChain(handler));

	// 获取url
	String lookupPath = this.urlPathHelper.getLookupPathForRequest(request, LOOKUP_PATH);
	for (HandlerInterceptor interceptor : this.adaptedInterceptors) { 
   
		if (interceptor instanceof MappedInterceptor) { 
   
			MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
			// 将url与interceptor配置的url进行匹配
			if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) { 
   
				// 能匹配上的interceptor加入到HandlerExecutionChain中
				chain.addInterceptor(mappedInterceptor.getInterceptor());
			}
		}
		else { 
   
			// 直接向容器中注入的MappedInterceptor
			// 没配置path的直接加入到HandlerExecutionChain中
			chain.addInterceptor(interceptor);
		}
	}
	return chain;
}

在handler执行之前HandlerInterceptor.interceptor：

org.springframework.web.servlet.HandlerExecutionChain#applyPreHandle

boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception { 
   
	HandlerInterceptor[] interceptors = getInterceptors();
	if (!ObjectUtils.isEmpty(interceptors)) { 
   
		for (int i = 0; i < interceptors.length; i++) { 
   
			HandlerInterceptor interceptor = interceptors[i];
			// 调用HandlerInterceptor.preHandle
			if (!interceptor.preHandle(request, response, this.handler)) { 
   
				// 调用HandlerInterceptor.afterCompletion
				triggerAfterCompletion(request, response, null);
				return false;
			}
			this.interceptorIndex = i;
		}
	}
	return true;
}

这里要注意的是调用了HandlerInterceptor的preHandle()方法就一定会调用HandlerInterceptor的afterCompletion()，假如目前有A、B、C三个Interceptor，执行了A和B的preHandle()，在执行C的preHandle()方法时返回false，那么还是执行A和B的afterCompletion()，而且是先执行B.afterCompletion()，再执行A.afterCompletion()。

在handler执行之后，视图解析之前执行HandlerInterceptor.postHandle：

org.springframework.web.servlet.HandlerExecutionChain#applyPostHandle

void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)
	throws Exception { 
   

	HandlerInterceptor[] interceptors = getInterceptors();
	if (!ObjectUtils.isEmpty(interceptors)) { 
   
		// i在这里是从大到小，也就是按interceptors的逆序执行
		for (int i = interceptors.length - 1; i >= 0; i--) { 
   
			HandlerInterceptor interceptor = interceptors[i];
			// 调用HandlerInterceptor.postHandle
			interceptor.postHandle(request, response, this.handler, mv);
		}
	}
}

在视图渲染之后执行HandlerInterceptor.afterCompletion：

org.springframework.web.servlet.HandlerExecutionChain#triggerAfterCompletion

void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex)
	throws Exception { 
   

	HandlerInterceptor[] interceptors = getInterceptors();
	if (!ObjectUtils.isEmpty(interceptors)) { 
   
		// i在这里是从大到小，也就是按interceptors的逆序执行
		for (int i = this.interceptorIndex; i >= 0; i--) { 
   
			HandlerInterceptor interceptor = interceptors[i];
			try { 
   
				// 调用HandlerInterceptor.afterCompletion
				interceptor.afterCompletion(request, response, this.handler, ex);
			}
			catch (Throwable ex2) { 
   
				logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
			}
		}
	}
}