SpringMVC中HandlerMethod的请求参数解析过程

1. private Object[] resolveHandlerArguments(Method handlerMethod, Object handler,

2. NativeWebRequest webRequest, ExtendedModelMap implicitModel) throws Exception {

3.  

4. Class[] paramTypes = handlerMethod.getParameterTypes();

5. Object[] args = new Object[paramTypes.length];

6.  

7. for (int i = 0; i < args.length; i++) {

8. MethodParameter methodParam = new MethodParameter(handlerMethod, i);

9. methodParam.initParameterNameDiscovery(this.parameterNameDiscoverer);

10. GenericTypeResolver.resolveParameterType(methodParam, handler.getClass());

11. String paramName = null;

12. String headerName = null;

13. boolean requestBodyFound = false;

14. String cookieName = null;

15. String pathVarName = null;

16. String attrName = null;

17. boolean required = false;

18. String defaultValue = null;

19. boolean validate = false;

20. Object[] validationHints = null;

21. int annotationsFound = 0;

22. Annotation[] paramAnns = methodParam.getParameterAnnotations();

23.  

24. for (Annotation paramAnn : paramAnns) {

25. if (RequestParam.class.isInstance(paramAnn)) {

26. RequestParam requestParam = (RequestParam) paramAnn;

27. paramName = requestParam.value();

28. required = requestParam.required();

29. defaultValue = parseDefaultValueAttribute(requestParam.defaultValue());

30. annotationsFound++;

31. }

32. else if (RequestHeader.class.isInstance(paramAnn)) {

33. RequestHeader requestHeader = (RequestHeader) paramAnn;

34. headerName = requestHeader.value();

35. required = requestHeader.required();

36. defaultValue = parseDefaultValueAttribute(requestHeader.defaultValue());

37. annotationsFound++;

38. }

39. else if (RequestBody.class.isInstance(paramAnn)) {

40. requestBodyFound = true;

41. annotationsFound++;

42. }

43. else if (CookieValue.class.isInstance(paramAnn)) {

44. CookieValue cookieValue = (CookieValue) paramAnn;

45. cookieName = cookieValue.value();

46. required = cookieValue.required();

47. defaultValue = parseDefaultValueAttribute(cookieValue.defaultValue());

48. annotationsFound++;

49. }

50. else if (PathVariable.class.isInstance(paramAnn)) {

51. PathVariable pathVar = (PathVariable) paramAnn;

52. pathVarName = pathVar.value();

53. annotationsFound++;

54. }

55. else if (ModelAttribute.class.isInstance(paramAnn)) {

56. ModelAttribute attr = (ModelAttribute) paramAnn;

57. attrName = attr.value();

58. annotationsFound++;

59. }

60. else if (Value.class.isInstance(paramAnn)) {

61. defaultValue = ((Value) paramAnn).value();

62. }

63. else if (paramAnn.annotationType().getSimpleName().startsWith("Valid")) {

64. validate = true;

65. Object value = AnnotationUtils.getValue(paramAnn);

66. validationHints = (value instanceof Object[] ? (Object[]) value : new Object[] {value});

67. }

68. }

69.  

70. if (annotationsFound > 1) {

71. throw new IllegalStateException("Handler parameter annotations are exclusive choices - " +

72. "do not specify more than one such annotation on the same parameter: " + handlerMethod);

73. }

74.  

75. if (annotationsFound == 0) {

76. Object argValue = resolveCommonArgument(methodParam, webRequest);

77. if (argValue != WebArgumentResolver.UNRESOLVED) {

78. args[i] = argValue;

79. }

80. else if (defaultValue != null) {

81. args[i] = resolveDefaultValue(defaultValue);

82. }

83. else {

84. Class<?> paramType = methodParam.getParameterType();

85. if (Model.class.isAssignableFrom(paramType) || Map.class.isAssignableFrom(paramType)) {

86. if (!paramType.isAssignableFrom(implicitModel.getClass())) {

87. throw new IllegalStateException("Argument [" + paramType.getSimpleName() + "] is of type " +

88. "Model or Map but is not assignable from the actual model. You may need to switch " +

89. "newer MVC infrastructure classes to use this argument.");

90. }

91. args[i] = implicitModel;

92. }

93. else if (SessionStatus.class.isAssignableFrom(paramType)) {

94. args[i] = this.sessionStatus;

95. }

96. else if (HttpEntity.class.isAssignableFrom(paramType)) {

97. args[i] = resolveHttpEntityRequest(methodParam, webRequest);

98. }

99. else if (Errors.class.isAssignableFrom(paramType)) {

100. throw new IllegalStateException("Errors/BindingResult argument declared " +

101. "without preceding model attribute. Check your handler method signature!");

102. }

103. else if (BeanUtils.isSimpleProperty(paramType)) {

104. paramName = "";

105. }

106. else {

107. attrName = "";

108. }

109. }

110. }

111.  

112. if (paramName != null) {

113. args[i] = resolveRequestParam(paramName, required, defaultValue, methodParam, webRequest, handler);

114. }

115. else if (headerName != null) {

116. args[i] = resolveRequestHeader(headerName, required, defaultValue, methodParam, webRequest, handler);

117. }

118. else if (requestBodyFound) {

119. args[i] = resolveRequestBody(methodParam, webRequest, handler);

120. }

121. else if (cookieName != null) {

122. args[i] = resolveCookieValue(cookieName, required, defaultValue, methodParam, webRequest, handler);

123. }

124. else if (pathVarName != null) {

125. args[i] = resolvePathVariable(pathVarName, methodParam, webRequest, handler);

126. }

127. else if (attrName != null) {

128. WebDataBinder binder =

129. resolveModelAttribute(attrName, methodParam, implicitModel, webRequest, handler);

130. boolean assignBindingResult = (args.length > i + 1 && Errors.class.isAssignableFrom(paramTypes[i + 1]));

131. if (binder.getTarget() != null) {

132. doBind(binder, webRequest, validate, validationHints, !assignBindingResult);

133. }

134. args[i] = binder.getTarget();

135. if (assignBindingResult) {

136. args[i + 1] = binder.getBindingResult();

137. i++;

138. }

139. implicitModel.putAll(binder.getBindingResult().getModel());

140. }

141. }

142.  

143. return args;

144. }

  这个方法的调用关系如下图所示，