Springboot拦截器使用及其底层源码剖析

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"博主最近看了一下公司刚刚开发的微服务，准备入手从基本的过滤器以及拦截器开始剖析，以及在帮同学们分析一下上次的jetty过滤器源码与本次Springboot中tomcat中过滤器的区别。正题开始，拦截器顾名思义是进行拦截请求的一系列操作。先给大家示例一下使用操作"}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"1 @Configuration\n2 public class WebConfiguration implements WebMvcConfigurer {\n3 \n4 @Override\n5 public void addInterceptors(InterceptorRegistry registry) {\n6 registry.addInterceptor(new TstCfg());\n7 }\n8 }"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":" 1 /**\n 2 * @title: TstCfg\n 3 * @Author junyu\n 4 * 旧巷里有一个穿着白衬衫笑起来如太阳般温暖我的少年。\n 5 * 记忆里有一个穿着连衣裙哭起来如孩子般讨人喜的女孩。\n 6 * 他说，哪年树弯了腰，人见了老，桃花落了白发梢，他讲的笑话她还会笑，那便是好。\n 7 * 她说，哪年国改了号，坟长了草，地府过了奈何桥，她回头看时他还在瞧，就不算糟。\n 8 * @Date: 2020/7/29 11:53\n 9 * @Version 1.0\n10 */\n11 public class TstCfg extends HandlerInterceptorAdapter {\n12 \n13 @Override\n14 public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {\n15 System.out.println(\"前\");\n16 return super.preHandle(request, response, handler);\n17 }\n18 \n19 @Override\n20 public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {\n21 System.out.println(\"后\");\n22 }\n23 \n24 @Override\n25 public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {\n26 System.out.println(\"一直会出现\");\n27 System.out.println(1/0);\n28 }\n29 }"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"首先我们可能会想到，我们的拦截器是何时装配到拦截器数组中"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　其实就是在springboot启动时执行doCreateBean时，进行调用创建的org.springframework.boot.autoconfigure.web.servlet.WebMvcAutoConfiguration$EnableWebMvcConfiguration会在这里放入进去所有实现了WebMvcConfigurer接口的类，一共有7个，其中就有我们自己实现了WebMvcConfigurer接口的WebConfiguration类，"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/77/77276a0638d6e124c71070f5ceee6115.png","alt":"","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"我们的写的配置类WebConfiguration，继承了WebMvcConfigurer并重写了addInterceptors方法，所以我们的拦截器就在这时候装配进去了。这次知道为什么我们写的配置拦截器的配置示例需要继承------WebMvcConfigurer，我们当然也可以去继承已经实现了这个类的其他类，因为都可以去添加拦截器，博主亲试过，所以就不贴图了！"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/56/56b3d1aefd182aecd73eb96ec801971b.png","alt":"","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　　 好了，拦截器已经添加完了，那什么时候调用我们拦截器呢？一步一步脚印来，当浏览器请求我们地址的 时候，分一下几步："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"　第一步：tomcat容器首先会接受到请求，这里将会走DispatcherServlet，看到这个大家都熟悉了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/e6/e65dde8ef7900ca7e2a5b4115fe5dce7.png","alt":"","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 第二步：当然不会先走我们的拦截器了，我们的拦截器是在Springboot框架进行管理的，现在还在servlet，所以会先走到filter过滤器这一步，来贴图：官方代码太长，一屏截不下，前面有一个创建过滤器链的过程：等下次在给大家讲一下jetty的过滤器链与tomcat的过滤器链的区别"}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"ApplicationFilterChain filterChain = ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/46/46f77cfd2722babe4a1053ee4f42bd70.png","alt":"","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 第三步：所以一旦连过滤器都没通过的话，会直接return回去，不会再进行拦截器的调用。来贴代码，过滤器通过后如何调用我们拦截器的"}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"1 private void internalDoFilter(ServletRequest request,\n 2 ServletResponse response)\n 3 throws IOException, ServletException {\n 4 //这里将会调用所有过滤器链的过滤器，不做重点讲解了，看看下面拦截器的调用\n 5 // Call the next filter if there is one\n 6 if (pos < n) {\n 7 ApplicationFilterConfig filterConfig = filters[pos++];\n 8 try {\n 9 Filter filter = filterConfig.getFilter();\n10 \n11 if (request.isAsyncSupported() && \"false\".equalsIgnoreCase(\n12 filterConfig.getFilterDef().getAsyncSupported())) {\n13 request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR, Boolean.FALSE);\n14 }\n15 if( Globals.IS_SECURITY_ENABLED ) {\n16 final ServletRequest req = request;\n17 final ServletResponse res = response;\n18 Principal principal =\n19 ((HttpServletRequest) req).getUserPrincipal();\n20 \n21 Object[] args = new Object[]{req, res, this};\n22 SecurityUtil.doAsPrivilege (\"doFilter\", filter, classType, args, principal);\n23 } else {\n24 filter.doFilter(request, response, this);\n25 }\n26 } catch (IOException | ServletException | RuntimeException e) {\n27 throw e;\n28 } catch (Throwable e) {\n29 e = ExceptionUtils.unwrapInvocationTargetException(e);\n30 ExceptionUtils.handleThrowable(e);\n31 throw new ServletException(sm.getString(\"filterChain.filter\"), e);\n32 }\n33 return;\n34 }\n35 \n36 // We fell off the end of the chain -- call the servlet instance\n37 try {\n38 if (ApplicationDispatcher.WRAP_SAME_OBJECT) {\n39 lastServicedRequest.set(request);\n40 lastServicedResponse.set(response);\n41 }\n42 \n43 if (request.isAsyncSupported() && !servletSupportsAsync) {\n44 request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR,\n45 Boolean.FALSE);\n46 }\n47 // Use potentially wrapped request from this point\n48 if ((request instanceof HttpServletRequest) &&\n49 (response instanceof HttpServletResponse) &&\n50 Globals.IS_SECURITY_ENABLED ) {\n51 final ServletRequest req = request;\n52 final ServletResponse res = response;\n53 Principal principal =\n54 ((HttpServletRequest) req).getUserPrincipal();\n55 Object[] args = new Object[]{req, res};\n56 SecurityUtil.doAsPrivilege(\"service\",\n57 servlet,\n58 classTypeUsedInService,\n59 args,\n60 principal);\n61 } else {\n62 //过滤器终于完事了，现在终于开始正式调用我们的方法了，我们看看service方法做了什么吧！\n63 servlet.service(request, response);\n64 }\n65 } catch (IOException | ServletException | RuntimeException e) {\n66 throw e;\n67 } catch (Throwable e) {\n68 e = ExceptionUtils.unwrapInvocationTargetException(e);\n69 ExceptionUtils.handleThrowable(e);\n70 throw new ServletException(sm.getString(\"filterChain.servlet\"), e);\n71 } finally {\n72 if (ApplicationDispatcher.WRAP_SAME_OBJECT) {\n73 lastServicedRequest.set(null);\n74 lastServicedResponse.set(null);\n75 }\n76 }\n77 } \n复制代码"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其实最终它会调用到DispatcherServlet的doDispatch方法"}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":" 1 protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {\n 2 HttpServletRequest processedRequest = request;\n 3 HandlerExecutionChain mappedHandler = null;\n 4 boolean multipartRequestParsed = false;\n 5 \n 6 WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);\n 7 \n 8 try {\n 9 ModelAndView mv = null;\n10 Exception dispatchException = null;\n11 \n12 try {\n13 processedRequest = checkMultipart(request);\n14 multipartRequestParsed = (processedRequest != request);\n15 \n16 // Determine handler for the current request.\n17 mappedHandler = getHandler(processedRequest);\n18 if (mappedHandler == null) {\n19 noHandlerFound(processedRequest, response);\n20 return;\n21 }\n22 \n23 // Determine handler adapter for the current request.\n24 HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());\n25 \n26 // Process last-modified header, if supported by the handler.\n27 String method = request.getMethod();\n28 boolean isGet = \"GET\".equals(method);\n29 if (isGet || \"HEAD\".equals(method)) {\n30 long lastModified = ha.getLastModified(request, mappedHandler.getHandler());\n31 if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {\n32 return;\n33 }\n34 }\n35 //所有拦截器开始在调用方法前拦截，如果你拦截器中返回false，则直接return不会再调用该方法！下面有源代码\n36 if (!mappedHandler.applyPreHandle(processedRequest, response)) {\n37 return;\n38 }\n39 \n40 // Actually invoke the handler.\n41 //底层进行invoke反射，调用当前请求的方法，不用再往里面看了\n42 mv = ha.handle(processedRequest, response, mappedHandler.getHandler());\n43 \n44 if (asyncManager.isConcurrentHandlingStarted()) {\n45 return;\n46 }\n47 \n48 applyDefaultViewName(processedRequest, mv);\n49 //调用拦截器的postHandle，下面有源代码\n50 mappedHandler.applyPostHandle(processedRequest, response, mv);\n51 }\n52 catch (Exception ex) {\n53 dispatchException = ex;\n54 }\n55 catch (Throwable err) {\n56 // As of 4.3, we're processing Errors thrown from handler methods as well,\n57 // making them available for @ExceptionHandler methods and other scenarios.\n58 dispatchException = new NestedServletException(\"Handler dispatch failed\", err);\n59 }\n60 //该方法中多做了一些逻辑，其实最后也调用了triggerAfterCompletion方法，最终调用拦截器方法的afterCompletion方法\n61 processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);\n62 }\n63 catch (Exception ex) {\n64 //所以不管是否出现异常，拦截器方法的afterCompletion方法是一定会调用的！\n65 triggerAfterCompletion(processedRequest, response, mappedHandler, ex);\n66 }\n67 catch (Throwable err) {\n68 //所以不管是否出现异常，拦截器方法的afterCompletion方法是一定会调用的！\n69 triggerAfterCompletion(processedRequest, response, mappedHandler,\n70 new NestedServletException(\"Handler processing failed\", err));\n71 }\n72 finally {\n73 if (asyncManager.isConcurrentHandlingStarted()) {\n74 // Instead of postHandle and afterCompletion\n75 if (mappedHandler != null) {\n76 mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);\n77 }\n78 }\n79 else {\n80 // Clean up any resources used by a multipart request.\n81 if (multipartRequestParsed) {\n82 cleanupMultipart(processedRequest);\n83 }\n84 }\n85 }\n86 }\n复制代码"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"现在终于开始了我们拦截器的方法了，一个一个来："}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"1 boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {\n 2 HandlerInterceptor[] interceptors = getInterceptors();\n 3 if (!ObjectUtils.isEmpty(interceptors)) {\n 4 for (int i = 0; i < interceptors.length; i++) {\n 5 HandlerInterceptor interceptor = interceptors[i];\n 6 //调用所有拦截器的preHandle方法\n 7 if (!interceptor.preHandle(request, response, this.handler)) {\n 8 //就算preHandle方法没有通过，仍然会调用这个triggerAfterCompletion方法。\n 9 triggerAfterCompletion(request, response, null);\n10 return false;\n11 }\n12 this.interceptorIndex = i;\n13 }\n14 }\n15 return true;\n16 }"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":" 1 void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv)\n 2 throws Exception {\n 3 \n 4 HandlerInterceptor[] interceptors = getInterceptors();\n 5 if (!ObjectUtils.isEmpty(interceptors)) {\n 6 for (int i = interceptors.length - 1; i >= 0; i--) {\n 7 HandlerInterceptor interceptor = interceptors[i];\n 8 //调用拦截器的postHandle方法，\n 9 interceptor.postHandle(request, response, this.handler, mv);\n10 }\n11 }\n12 }"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":" 1 void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex)\n 2 throws Exception {\n 3 \n 4 HandlerInterceptor[] interceptors = getInterceptors();\n 5 if (!ObjectUtils.isEmpty(interceptors)) {\n 6 for (int i = this.interceptorIndex; i >= 0; i--) {\n 7 HandlerInterceptor interceptor = interceptors[i];\n 8 try {\n 9 //调用拦截器的afterCompletion方法，不管是否异常都会进行调用，但是如果该方法报异常，会被抓住。\n10 //不会影响程序正常运行，只会打印出来\n11 interceptor.afterCompletion(request, response, this.handler, ex);\n12 }\n13 catch (Throwable ex2) {\n14 logger.error(\"HandlerInterceptor.afterCompletion threw exception\", ex2);\n15 }\n16 }\n17 }\n18 }"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面这个就是打印了一下，但是不会影响我们的请求响应回去："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/3c/3c174ead44f54a5211b268d30a69a2e6.png","alt":"","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 还是会正常响应回客户端："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/04/04b1660e3af45461268afefe9e742a40.png","alt":"","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":" 好了，到此拦截器的实现以及源码分析流程到此结束，本来想给大家从Springboot的reflash方法开始解析拦截器，但是内容太多了，不仅跑题而且博主也一时半会给大家无法讲解明白。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}