Question

我正在尝试在我的spring mvc项目中添加自定义解析器。解析器代码在这里：

public class CurrentUserWebArgumentResolver implements WebArgumentResolver {

    @Override
    public Object resolveArgument(MethodParameter methodParameter, NativeWebRequest webRequest) throws Exception {
        if (methodParameter.getParameterType().equals(User.class)) {
            User host = (User)webRequest.getAttribute(WebConstant.HTTP_REQUEST_HOST_NAME, RequestAttributes.SCOPE_REQUEST);
            return host;
        }
        return null;
    }
}

我更改了默认注释spring config：

<mvc:annotation-driven >
        <mvc:argument-resolvers>
            <bean class="com.xxx.web.resolver.CurrentUserWebArgumentResolver" />
        </mvc:argument-resolvers>
    </mvc:annotation-driven>

我的控制器功能在这里：

@RequestMapping(value = "register", method = RequestMethod.POST)
    public ModelAndView store(@Valid RegisterForm registerForm, BindingResult result) {
        ModelAndView mv = new ModelAndView("user/register");
        if (result.hasErrors()) {
            return mv;
        }
        User user = registerForm.getUser();
        if (registerService.register(user)) {
            mv.setView(new RedirectView("/"));
        }
        return mv;
    }

现在，当我请求此网址时，我收到此错误：

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.IllegalStateException: An Errors/BindingResult argument is expected to be declared immediately after the model attribute, the @RequestBody or the @RequestPart arguments to which they apply: public org.springframework.web.servlet.ModelAndView com.xxx.web.controller.user.RegisterController.store(com.xxx.web.validate.form.user.RegisterForm,org.springframework.validation.BindingResult)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:927)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:822)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:796)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.lang.IllegalStateException: An Errors/BindingResult argument is expected to be declared immediately after the model attribute, the @RequestBody or the @RequestPart arguments to which they apply: public org.springframework.web.servlet.ModelAndView com.xxx.web.controller.user.RegisterController.store(com.xxx.web.validate.form.user.RegisterForm,org.springframework.validation.BindingResult)
    org.springframework.web.method.annotation.ErrorsMethodArgumentResolver.resolveArgument(ErrorsMethodArgumentResolver.java:62)
    org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:77)
    org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:162)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:123)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:746)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:687)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:915)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:822)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:796)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

我认为必须有一些其他解析器我没有添加到spring配置文件

请帮助我谢谢

Answer 1

您违反了contract

返回：参数值，如果不可解析则返回UNRESOLVED

您正在返回违反合同的null。替换为UNRESOLVED静态变量。

public class CurrentUserWebArgumentResolver implements WebArgumentResolver {

    @Override
    public Object resolveArgument(MethodParameter methodParameter, NativeWebRequest webRequest) throws Exception {
        if (methodParameter.getParameterType().equals(User.class)) {
            User host = (User)webRequest.getAttribute(WebConstant.HTTP_REQUEST_HOST_NAME, RequestAttributes.SCOPE_REQUEST);
            return host;
        }
        return UNRESOLVED;
    }
}

spring mvc添加自定义解析器并获得500错误

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