最近在了解GraphQL，根据https://www.graphql-java.com/tutorials/getting-started-with-spring-boot/里面的例子搭建了一个demo，结果在使用GraphQL playground来查看GraphQL demo结果的时候，报错：

Failed to fetch. Please check your connection

F12查看前台请求，发现报错为：

Access to fetch at ‘http://localhost:8080/graphql’ from origin
‘https://www.graphqlbin.com’ has been blocked by CORS policy: No
‘Access-Control-Allow-Origin’ header is present on the requested
resource. If an opaque response serves your needs, set the request’s
mode to ‘no-cors’ to fetch the resource with CORS disabled.

所以原因是跨域问题。

Spring MVC配置CORS的方式，搜索了一下找到一个博客
Spring MVC配置CORS（解决跨域请求）

采用其中的添加全局配置的方式，解决了问题。

GraphQL playground可以调用到后台的demo了!