springmvc的controller可以访问但不能返回map类型的数据

 1、首先，web.xml加上这一段配置：

<!-- 启动Spring MVC的注解功能，完成请求和注解POJO的映射 -->
	<bean
		class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
		<property name="messageConverters">
			<list>
				<!--json转换器 -->
				<ref bean="mappingJacksonHttpMessageConverter" />
			</list>
		</property>
	</bean>
	<bean
		class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
		<property name="messageConverters">
			<list>
				<ref bean="mappingJacksonHttpMessageConverter" />
			</list>
		</property>
	</bean>

	<bean id="mappingJacksonHttpMessageConverter"
		class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
		<property name="supportedMediaTypes">
			<list>
				<bean class="org.springframework.http.MediaType">
					<constructor-arg index="0" value="text" />
					<constructor-arg index="1" value="plain" />
					<constructor-arg index="2" value="UTF-8" />
				</bean>
				<bean class="org.springframework.http.MediaType">
					<constructor-arg index="0" value="*" />
					<constructor-arg index="1" value="*" />
					<constructor-arg index="2" value="UTF-8" />
				</bean>
				<bean class="org.springframework.http.MediaType">
					<constructor-arg index="0" value="text" />
					<constructor-arg index="1" value="*" />
					<constructor-arg index="2" value="UTF-8" />
				</bean>
				<bean class="org.springframework.http.MediaType">
					<constructor-arg index="0" value="application" />
					<constructor-arg index="1" value="json" />
					<constructor-arg index="2" value="UTF-8" />
				</bean>
			</list>
		</property>
	</bean>  

2、 controller这样写：

@Controller
@RequestMapping("/dfc")
public class dfcController {
	@Autowired
	@Qualifier("dataflow_connectionInfo_service")
	private Idataflow_connectionInfo service = new dataflow_connectionInfo_service_impl();
	
	// 查询数据
	@RequestMapping(value="/getDFC",method=RequestMethod.GET)
	@ResponseBody
	public Map<String, Object> doSelectDfc() {
		return service.findAllDfc();
	}
	
	@RequestMapping("/getJson")
	@ResponseBody
	public String doGet() {
		return "11111111";
	}
	
	// 插入数据
	@RequestMapping("/insertDFC")
	public Object doInsertDfc(dataflow_connectionInfo info) {

		if (service.addDfc(info)) {
			return true;
		} else {
			return false;
		}
	}
}

3、 重新导2.7版本的jackson相关包： 
jackson-databind-2.7.4.jar 
jackson-annotations-2.7.4.jar 
jackson-core-2.7.4.jar

以上jar包下载地址（拷贝下面URL在新页面打开，不然下载不了）： 
http://cdn.sojson.com/file/16-05-03-20-51-11/json-jar.zip

参考：https://blog.csdn.net/gsycwh/article/details/56675836