完整错误： Request processing failed; nested exception is java.lang.IllegalArgumentException: No converter found for return value of type: class ink.xlr.po.User
返回的对象User无法转换
解决办法：
在pom.xml中添加jackson(自动转换Java对象为json对象和xml文档)
<dependency>
<groupId>com
.fasterxml
.jackson
.core
</groupId
>
<artifactId>jackson
-databind
</artifactId
>
<version>2.9.0</version
>
</dependency
>
