SpringMVC return JSON failed to convert type Map

• 错误信息：WARN DefaultHandlerExceptionResolver:380 - Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: No converter found for return value of type: class java.util.HashMap

• Solution:

  Import dependence

    <dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.4</version>
    </dependency>