SpringMVC——数据绑定流程

た入场券 2022-05-21 01:21 221阅读 0赞

#### 一、流程 ####

Spring MVC 主框架将 ServletRequest • 对象及目标方法的入参实例传递给 WebDataBinderFactory 实例，以创建 DataBinder 实例对象2. DataBinder 调用装配在 Spring MVC 上下文中的 ConversionService 组件进行数据类型转换、数据格式化工作。将 Servlet 中的请求信息填充到入参对象中3. 调用 Validator 组件对已经绑定了请求消息的入参对象进行数据合法性校验，并最终生成数据绑定结果BindingData 对象4. Spring MVC 抽取 BindingResult 中的入参对象和校验错误对象，将它们赋给处理方法的响应入参

![70][]

二、源码分析：

public class ModelAttributeMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler {
        protected final Log logger = LogFactory.getLog(this.getClass());
        private final boolean annotationNotRequired;
    
        public ModelAttributeMethodProcessor(boolean annotationNotRequired) {
            this.annotationNotRequired = annotationNotRequired;
        }
    
        public boolean supportsParameter(MethodParameter parameter) {
            return parameter.hasParameterAnnotation(ModelAttribute.class) || this.annotationNotRequired && !BeanUtils.isSimpleProperty(parameter.getParameterType());
        }
    
        public final Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
            String name = ModelFactory.getNameForParameter(parameter);
            ModelAttribute ann = (ModelAttribute)parameter.getParameterAnnotation(ModelAttribute.class);
            if (ann != null) {
                mavContainer.setBinding(name, ann.binding());
            }
    
            Object attribute = mavContainer.containsAttribute(name) ? mavContainer.getModel().get(name) : this.createAttribute(name, parameter, binderFactory, webRequest);
           WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name); if (binder.getTarget() != null) { if (!mavContainer.isBindingDisabled(name)) { this.bindRequestParameters(binder, webRequest); } this.validateIfApplicable(binder, parameter); if (binder.getBindingResult().hasErrors() && this.isBindExceptionRequired(binder, parameter)) { throw new BindException(binder.getBindingResult()); } }
    
            Map<String, Object> bindingResultModel = binder.getBindingResult().getModel();
            mavContainer.removeAttributes(bindingResultModel);
            mavContainer.addAllAttributes(bindingResultModel);
            return binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter);
        }

![70 1][]

[70]: /images/20220521/65deb6774c104e71b2333356f905f454.png
[70 1]: /images/20220521/6290aaf8b8494b4491ab9d93f1d1bb96.png