When springboot uses TestRestTemplate unit test, it prompts ResourceAccess I/O error on POST request for "http

I found that if the http status code in the background returns 401, this will happen (other 4XX, etc. may also be)

Solution, join

 <dependency>
     <groupId></groupId>
     <artifactId>httpclient</artifactId>
     <scope>test</scope>
 </dependency>