前言

自研究了spring security核心原始碼以來,在實踐使用的基礎上更為深入的學習了它的思想.我的java世界彷彿被打開了一扇大門,開始對研究原始碼有種渴望.打算先看一輪核心原始碼,滿足目前工作需要,待對boot有個整體的瞭解之後再逐個細細研究

spring mvc核心流程圖

流程說明:

1. 使用者傳送請求到dispatcherServlet,它執行父類frameworkServlet的service方法,service()->processRequest()開始處理請求,processRequest()->doService()->doDispatch();這一段都是給request里加入一些spring的bean,然後處理一下request
2. dispatcherServlet遍歷自己的handlerMapping,當正確的handlerMapping找到handlerExcutionChain的時候返回,給dispatchServlet.(chain裡主要是一個handlerAdapter和一些攔截器)
3. handlerExcutionChain開始攔截器處理請求,然後呼叫handlerAdapter裡的handler()方法,handler()->AbstractHandlerMethodAdapter裡的handleInternal(),然後反射執行我們controller裡的業務邏輯,將得到的modelAndView物件返回給dispatchServlet,然後繼續執行攔截器方法.
4. dispacherServlet  呼叫processDispatchResult把得到的modelAndView交給viewResolve去render檢視

原始碼一覽

1. protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {

2. HttpServletRequest processedRequest = request;

3. HandlerExecutionChain mappedHandler = null;

4. boolean multipartRequestParsed = false;

5. WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

6. try {

7. try {

8. ModelAndView mv = null;

9. Object dispatchException = null;

10. try {

11. //是否檔案上傳

12. processedRequest = this.checkMultipart(request);

13. multipartRequestParsed = processedRequest != request;

14.   //獲取handlerExcutionChain

15. mappedHandler = this.getHandler(processedRequest);

16. if (mappedHandler == null) {

17. this.noHandlerFound(processedRequest, response);

18. return;

19. }

20. //獲取handlerAdapter

21. HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());

22. String method = request.getMethod();

23. boolean isGet = "GET".equals(method);

24. if (isGet || "HEAD".equals(method)) {

25. long lastModified = ha.getLastModified(request, mappedHandler.getHandler());

26. if (this.logger.isDebugEnabled()) {

27. this.logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);

28. }

29. if ((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {

30. return;

31. }

32. }

33. //呼叫攔截器們的前置方法

34. if (!mappedHandler.applyPreHandle(processedRequest, response)) {

35. return;

36. }

37. //呼叫controller裡的業務邏輯方法並返回modelAndView

38. mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

39. if (asyncManager.isConcurrentHandlingStarted()) {

40. return;

41. }

42. this.applyDefaultViewName(processedRequest, mv);

43.   //呼叫攔截器的後置方法

44. mappedHandler.applyPostHandle(processedRequest, response, mv);

45. } catch (Exception var20) {

46. dispatchException = var20;

47. } catch (Throwable var21) {

48. dispatchException = new NestedServletException("Handler dispatch failed", var21);

49. }

50. //把modelAndView交給viewResolver去render檢視

51. this.processDispatchResult(processedRequest, response, mappedHandler, mv, (Exception)dispatchException);

52. } catch (Exception var22) {

53. this.triggerAfterCompletion(processedRequest, response, mappedHandler, var22);

54. } catch (Throwable var23) {

55. this.triggerAfterCompletion(processedRequest, response, mappedHandler, new NestedServletException("Handler processing failed", var23));

56. }

57. } finally {

58. if (asyncManager.isConcurrentHandlingStarted()) {

59. if (mappedHandler != null) {

60. mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);

61. }

62. } else if (multipartRequestParsed) {

63. this.cleanupMultipart(processedRequest);

64. }

65. }

66. }

1. 獲取handlerExcutionChain物件

2. protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {

3. if (this.handlerMappings != null) {

4. Iterator var2 = this.handlerMappings.iterator();

5. while(var2.hasNext()) {

6. HandlerMapping hm = (HandlerMapping)var2.next();

7. if (this.logger.isTraceEnabled()) {

8. this.logger.trace("Testing handler map [" + hm + "] in DispatcherServlet with name '" + this.getServletName() + "'");

9. }

10. HandlerExecutionChain handler = hm.getHandler(request);

11. if (handler != null) {

12. return handler;

13. }

14. }

15. }

呼叫攔截器的前置方法

1. boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {

2. HandlerInterceptor[] interceptors = this.getInterceptors();

3. if (!ObjectUtils.isEmpty(interceptors)) {

4. for(int i = 0; i < interceptors.length; this.interceptorIndex = i++) {

5. HandlerInterceptor interceptor = interceptors[i];

6. if (!interceptor.preHandle(request, response, this.handler)) {

7. this.triggerAfterCompletion(request, response, (Exception)null);

8. return false;

9. }

10. }

11. }

12. return true;

13. }

//攔截器的後置方法

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

2. HandlerInterceptor[] interceptors = this.getInterceptors();

3. if (!ObjectUtils.isEmpty(interceptors)) {

4. for(int i = interceptors.length - 1; i >= 0; --i) {

5. HandlerInterceptor interceptor = interceptors[i];

6. interceptor.postHandle(request, response, this.handler, mv);

7. }

8. }

9. }

反射controller我們寫的邏輯

1. protected ModelAndView handleInternal(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {

2. this.checkRequest(request);

3. ModelAndView mav;

4. if (this.synchronizeOnSession) {

5. HttpSession session = request.getSession(false);

6. if (session != null) {

7. Object mutex = WebUtils.getSessionMutex(session);

8. synchronized(mutex) {

9. mav = this.invokeHandlerMethod(request, response, handlerMethod);

10. }

11. } else {

12. mav = this.invokeHandlerMethod(request, response, handlerMethod);

13. }

14. } else {

15. mav = this.invokeHandlerMethod(request, response, handlerMethod);

16. }

17. if (!response.containsHeader("Cache-Control")) {

18. if (this.getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {

19. this.applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);

20. } else {

21. this.prepareResponse(response);

22. }

23. }

24. return mav;

25. }

檢視渲染

1. private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, @Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv, @Nullable Exception exception) throws Exception {

2. boolean errorView = false;

3. if (exception != null) {

4. if (exception instanceof ModelAndViewDefiningException) {

5. this.logger.debug("ModelAndViewDefiningException encountered", exception);

6. mv = ((ModelAndViewDefiningException)exception).getModelAndView();

7. } else {

8. Object handler = mappedHandler != null ? mappedHandler.getHandler() : null;

9. mv = this.processHandlerException(request, response, handler, exception);

10. errorView = mv != null;

11. }

12. }

13. if (mv != null && !mv.wasCleared()) {

14. this.render(mv, request, response);

15. if (errorView) {

16. WebUtils.clearErrorRequestAttributes(request);

17. }

18. } else if (this.logger.isDebugEnabled()) {

19. this.logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + this.getServletName() + "': assuming HandlerAdapter completed request handling");

20. }

21. if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {

22. if (mappedHandler != null) {

23. mappedHandler.triggerAfterCompletion(request, response, (Exception)null);

24. }

25. }

26. }

總結

springmvc核心並不複雜,主要是圍繞dispatcherServlet,請朋友們自動動手debugger,這樣學習才會更有效