Tomcat对一个请求进行解析时,首先会进行最首先的封装,将请求封装成Request对象。
之后在一个类StandardWrapperValve中执行invoke方法。
之后在一个类StandardWrapperValve中执行invoke方法。
@Override public final void invoke(Request request, Response response) throws IOException, ServletException { // Initialize local variables we may need boolean unavailable = false; Throwable throwable = null; // This should be a Request attribute... long t1=System.currentTimeMillis(); requestCount.incrementAndGet(); StandardWrapper wrapper = (StandardWrapper) getContainer(); Servlet servlet = null; Context context = (Context) wrapper.getParent(); // Check for the application being marked unavailable if (!context.getState().isAvailable()) { response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE, sm.getString("standardContext.isUnavailable")); unavailable = true; } // Check for the servlet being marked unavailable if (!unavailable && wrapper.isUnavailable()) { container.getLogger().info(sm.getString("standardWrapper.isUnavailable", wrapper.getName())); long available = wrapper.getAvailable(); if ((available > 0L) && (available < Long.MAX_VALUE)) { response.setDateHeader("Retry-After", available); response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE, sm.getString("standardWrapper.isUnavailable", wrapper.getName())); } else if (available == Long.MAX_VALUE) { response.sendError(HttpServletResponse.SC_NOT_FOUND, sm.getString("standardWrapper.notFound", wrapper.getName())); } unavailable = true; } // Allocate a servlet instance to process this request try { if (!unavailable) { servlet = wrapper.allocate(); //在可用情况下分配servlet,可用看看 unavailable变量的取值 } } catch (UnavailableException e) { container.getLogger().error( sm.getString("standardWrapper.allocateException", wrapper.getName()), e); long available = wrapper.getAvailable(); if ((available > 0L) && (available < Long.MAX_VALUE)) { response.setDateHeader("Retry-After", available); response.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE, sm.getString("standardWrapper.isUnavailable", wrapper.getName())); } else if (available == Long.MAX_VALUE) { response.sendError(HttpServletResponse.SC_NOT_FOUND, sm.getString("standardWrapper.notFound", wrapper.getName())); } } catch (ServletException e) { container.getLogger().error(sm.getString("standardWrapper.allocateException", wrapper.getName()), StandardWrapper.getRootCause(e)); throwable = e; exception(request, response, e); } catch (Throwable e) { ExceptionUtils.handleThrowable(e); container.getLogger().error(sm.getString("standardWrapper.allocateException", wrapper.getName()), e); throwable = e; exception(request, response, e); servlet = null; } MessageBytes requestPathMB = request.getRequestPathMB(); DispatcherType dispatcherType = DispatcherType.REQUEST; if (request.getDispatcherType()==DispatcherType.ASYNC) dispatcherType = DispatcherType.ASYNC; request.setAttribute(Globals.DISPATCHER_TYPE_ATTR,dispatcherType); request.setAttribute(Globals.DISPATCHER_REQUEST_PATH_ATTR, requestPathMB); // Create the filter chain for this request ApplicationFilterChain filterChain = ApplicationFilterFactory.createFilterChain(request, wrapper, servlet); //重点,创建filterChain,根据代码实现的Filter // Call the filter chain for this request // NOTE: This also calls the servlet's service() method try { if ((servlet != null) && (filterChain != null)) { // Swallow output if needed if (context.getSwallowOutput()) { //swallowOutput 是Tomcat的Context的属性,用于设置System.out是否输出到日志,默认false try { SystemLogHandler.startCapture(); if (request.isAsyncDispatching()) { request.getAsyncContextInternal().doInternalDispatch(); } else { filterChain.doFilter(request.getRequest(), response.getResponse()); //重点,servlet和filter生效的地方 } } finally { String log = SystemLogHandler.stopCapture(); if (log != null && log.length() > 0) { context.getLogger().info(log); } } } else { if (request.isAsyncDispatching()) { request.getAsyncContextInternal().doInternalDispatch(); } else { filterChain.doFilter (request.getRequest(), response.getResponse());//重点,servlet和filter生效的地方 } } } } catch (ClientAbortException e) { }........捕获异常+后续内存释放等
line 43: //在可用情况下分配servlet,可用看看 unavailable变量的取值
line 82: //重点,创建filterChain,根据代码实现的Filter
line 89: swallowOutput 是Tomcat的Context的属性,用于设置System.out是否输出到日志,默认false
line 96 97 110//重点,servlet和filter生效的地方
继续跟进,看看filterChain.doFilter (request.getRequest(), response.getResponse());
@Override public void doFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException { if( Globals.IS_SECURITY_ENABLED ) { final ServletRequest req = request; final ServletResponse res = response; try { java.security.AccessController.doPrivileged( new java.security.PrivilegedExceptionAction<Void>() { @Override public Void run() throws ServletException, IOException { internalDoFilter(req,res);//重点方法 return null; } } ); } catch( PrivilegedActionException pe) { Exception e = pe.getException(); if (e instanceof ServletException) throw (ServletException) e; else if (e instanceof IOException) throw (IOException) e; else if (e instanceof RuntimeException) throw (RuntimeException) e; else throw new ServletException(e.getMessage(), e); } } else { internalDoFilter(request,response);//重点方法 } } private void internalDoFilter(ServletRequest request, ServletResponse response) throws IOException, ServletException { // Call the next filter if there is one if (pos < n) {//在 没有循环完filter时循环调用doFilter方法,一个责任链模式的经典实现 循环完跳出这个if方法块 ApplicationFilterConfig filterConfig = filters[pos++];//获取filterList由上面的createFilterChain创建 try { Filter filter = filterConfig.getFilter(); if (request.isAsyncSupported() && "false".equalsIgnoreCase( filterConfig.getFilterDef().getAsyncSupported())) { request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR, Boolean.FALSE); } if( Globals.IS_SECURITY_ENABLED ) { final ServletRequest req = request; final ServletResponse res = response; Principal principal = ((HttpServletRequest) req).getUserPrincipal(); Object[] args = new Object[]{req, res, this}; SecurityUtil.doAsPrivilege ("doFilter", filter, classType, args, principal); } else { filter.doFilter(request, response, this); } } catch (IOException | ServletException | RuntimeException e) { throw e; } catch (Throwable e) { e = ExceptionUtils.unwrapInvocationTargetException(e); ExceptionUtils.handleThrowable(e); throw new ServletException(sm.getString("filterChain.filter"), e); } return; } // We fell off the end of the chain -- call the servlet instance try { if (ApplicationDispatcher.WRAP_SAME_OBJECT) { lastServicedRequest.set(request); lastServicedResponse.set(response); } if (request.isAsyncSupported() && !servletSupportsAsync) { request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR, Boolean.FALSE); } // Use potentially wrapped request from this point if ((request instanceof HttpServletRequest) && (response instanceof HttpServletResponse) && Globals.IS_SECURITY_ENABLED ) { final ServletRequest req = request; final ServletResponse res = response; Principal principal = ((HttpServletRequest) req).getUserPrincipal(); Object[] args = new Object[]{req, res}; SecurityUtil.doAsPrivilege("service", servlet, classTypeUsedInService, args, principal); } else { servlet.service(request, response); //跳出循环后执行此方法,进入servlet的重点方法,对应到spring就是DispatcherServlet } } catch (IOException | ServletException | RuntimeException e) { throw e; } catch (Throwable e) { e = ExceptionUtils.unwrapInvocationTargetException(e); ExceptionUtils.handleThrowable(e); throw new ServletException(sm.getString("filterChain.servlet"), e); } finally { if (ApplicationDispatcher.WRAP_SAME_OBJECT) { lastServicedRequest.set(null); lastServicedResponse.set(null); } } }l ine 14: 继续调用
line 42,43: 责任链filter
line 98 :servlet的入口,对应到spring就是DispatcherServlet