Spring MVC 学习之 400 错误（1）

如果一个方法中有参数被 @Valid 标注了，但该参数后面没有紧跟一个 BindingResult 类型的参数，那么提交到该方法时，将返回 400 错误。

错误消息将会是：The request sent by the client was syntactically incorrect ().

错误的方法定义 1 ：（错误原因：没有 BindingResult 参数）

@RequestMapping ({ "error400" })
public String error400( @Valid @ModelAttribute ( "testForm" ) TestForm testForm) {
    return "test" ;
}

错误的方法定义 2 ：（错误原因：没有紧跟在 @Valid 参数之后）

@RequestMapping ({ "error400" })
public String error400( @Valid @ModelAttribute ( "testForm" ) TestForm testForm, Model model, Errors result) {
    return "demo/front/test" ;
}

也可参考 DefaultHandlerExceptionResolver.java 中的方法说明：

/**
 * Handle the case where an {@linkplain ModelAttribute @ModelAttribute} method
 * argument has binding or validation errors and is not followed by another
 * method argument of type {@link BindingResult}.
 * By default an HTTP 400 error is sent back to the client.
 * @param request current HTTP request
 * @param response current HTTP response
 * @param handler the executed handler
 * @return an empty ModelAndView indicating the exception was handled
 * @throws IOException potentially thrown from response.sendError()
 */
protected ModelAndView handleBindException(BindException ex, HttpServletRequest request,
        HttpServletResponse response, Object handler) throws IOException {
    response.sendError(HttpServletResponse.SC_BAD_REQUEST);
    return new ModelAndView();
}