前言

自研究了spring security核心源码以来,在实践使用的基础上更为深入的学习了它的思想.我的java世界仿佛被打开了一扇大门,开始对研究源码有种渴望.打算先看一轮核心源码,满足目前工作需要,待对boot有个整体的了解之后再逐个细细研究

spring mvc核心流程图

流程说明:

1. 用户发送请求到dispatcherServlet,它执行父类frameworkServlet的service方法,service()->processRequest()开始处理请求,processRequest()->doService()->doDispatch();这一段都是给request里加入一些spring的bean,然后处理一下request
2. dispatcherServlet遍历自己的handlerMapping,当正确的handlerMapping找到handlerExcutionChain的时候返回,给dispatchServlet.(chain里主要是一个handlerAdapter和一些拦截器)
3. handlerExcutionChain开始拦截器处理请求,然后调用handlerAdapter里的handler()方法,handler()->AbstractHandlerMethodAdapter里的handleInternal(),然后反射执行我们controller里的业务逻辑,将得到的modelAndView对象返回给dispatchServlet,然后继续执行拦截器方法.
4. dispacherServlet  调用processDispatchResult把得到的modelAndView交给viewResolve去render视图

源码一览

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.  

7. try {

8. try {

9. ModelAndView mv = null;

10. Object dispatchException = null;

11.  

12. try {

13. //是否文件上传

14. processedRequest = this.checkMultipart(request);

15. multipartRequestParsed = processedRequest != request;

16.   //获取handlerExcutionChain

17. mappedHandler = this.getHandler(processedRequest);

18. if (mappedHandler == null) {

19. this.noHandlerFound(processedRequest, response);

20. return;

21. }

22. //获取handlerAdapter

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

24. String method = request.getMethod();

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

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

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

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

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

30. }

31.  

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

33. return;

34. }

35. }

36. //调用拦截器们的前置方法

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

38. return;

39. }

40. //调用controller里的业务逻辑方法并返回modelAndView

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

42. if (asyncManager.isConcurrentHandlingStarted()) {

43. return;

44. }

45.  

46. this.applyDefaultViewName(processedRequest, mv);

47.   //调用拦截器的后置方法

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

49. } catch (Exception var20) {

50. dispatchException = var20;

51. } catch (Throwable var21) {

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

53. }

54. //把modelAndView交给viewResolver去render视图

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

56. } catch (Exception var22) {

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

58. } catch (Throwable var23) {

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

60. }

61.  

62. } finally {

63. if (asyncManager.isConcurrentHandlingStarted()) {

64. if (mappedHandler != null) {

65. mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);

66. }

67. } else if (multipartRequestParsed) {

68. this.cleanupMultipart(processedRequest);

69. }

70.  

71. }

72. }

1. 获取handlerExcutionChain对象

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

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

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

5.  

6. while(var2.hasNext()) {

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

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

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

10. }

11.  

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

13. if (handler != null) {

14. return handler;

15. }

16. }

17. }

调用拦截器的前置方法

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.  

13. return true;

14. }

//拦截器的后置方法

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.  

10. }

反射controller我们写的逻辑

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.  

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

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

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

21. } else {

22. this.prepareResponse(response);

23. }

24. }

25.  

26. return mav;

27. }

视图渲染

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.  

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

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

16. if (errorView) {

17. WebUtils.clearErrorRequestAttributes(request);

18. }

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

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

21. }

22.  

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

24. if (mappedHandler != null) {

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

26. }

27.  

28. }

29. }

总结

springmvc核心并不复杂,主要是围绕dispatcherServlet,请朋友们自动动手debugger,这样学习才会更有效