springMVC返回json格式数据报错：No converter found for return value of type: class java.util.HashMap

博主刚在写上一篇文章： SpringMVC异步上传多文件 的时候返回json格式对象，一直报错：

No converter found for return value of type: class java.util.HashMap    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:187)    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:174)    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:81)    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:132)    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)

总结：在springmvc中，如果使用@ResponseBody 返回json格式对象，需要导入jackson的jar包。

     <dependency>            <groupId>com.fasterxml.jackson.core</groupId>            <artifactId>jackson-core</artifactId>            <version>2.8.8</version>        </dependency>        <dependency>            <groupId>com.fasterxml.jackson.core</groupId>            <artifactId>jackson-annotations</artifactId>            <version>2.8.8</version>        </dependency>        <dependency>            <groupId>com.fasterxml.jackson.core</groupId>            <artifactId>jackson-databind</artifactId>            <version>2.8.8</version>        </dependency>