spring-mvc 运行报错 No adapter for handler

Question

配置了DispatcherServlet的detectAllHandlerMappings属性为true；
spring-mvc.xml也有声明：

<bean
        class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
    <property name="messageConverters">
        <list>
            <ref bean="mappingJacksonHttpMessageConverter" />    <!-- JSON转换器 -->
        </list>
    </property>
</bean>

**访问：http://localhost:8080/demo/index 一直报错：**
javax.servlet.ServletException: No adapter for handler [com.wch.controller.UserController@20142abf]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler
org.springframework.web.servlet.DispatcherServlet.getHandlerAdapter(DispatcherServlet.java:1136)

下面是Controller部分：
package com.wch.controller;

import com.wch.entity.User;
import com.wch.service.IUserService;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;

@Controller
public class UserController {

@Resource
private IUserService userService;

@RequestMapping(value = "/index", method = RequestMethod.GET)
public String toIndex(HttpServletRequest request, Model model)
{
    String name = (String)request.getParameter("name");
    User user = this.userService.getUser(name);
    model.addAttribute("user",user);
    return  "index";
}

}

Answer 1

知道原因了，原来我的controller里面使用了 @RequestMapping(value = "/index", method = RequestMethod.GET)这个注解，然后我的spring-mvc配置文件也注册了一个handlerAdapter,去掉这段就好了

<!--<bean-->
        <!--class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">-->
    <!--<property name="messageConverters">-->
        <!--<list>-->
            <!--<ref bean="mappingJacksonHttpMessageConverter" />    &lt;!&ndash; JSON转换器 &ndash;&gt;-->
        <!--</list>-->
    <!--</property>-->
<!--</bean>
具体原因说不上，还在研究

Answer 2

这样配置应该是没问题的

    <!-- 默认的注解映射的支持 -->
    <mvc:annotation-driven />
    <!-- 避免IE在ajax请求时，返回json出现下载 -->
    <bean id="jacksonMessageConverter"
        class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
        <property name="supportedMediaTypes">
            <list>
                <value>text/html;charset=UTF-8</value>
                <value>application/json;charset=UTF-8</value>
            </list>
        </property>
    </bean>

Answer 3

看起来没啥问题呢