官方文档
https://docs.spring.io/spring-framework/docs/5.2.8.RELEASE/javadoc-api/
https://docs.spring.io/spring-framework/docs/5.2.8.RELEASE/javadoc-api/org/springframework/web/client/RestTemplate.html
感谢
https://www.jianshu.com/p/90ec27b3b518(简单明了)
https://www.imooc.com/article/44796
建议使用exchange ，其他方法都是对execute进行了封装，都拥有各自的局限性。