HttpHeaders类:是一个Map(MultiValueMap<String, String> )
/**
* 1.定义了所有httpHead字段名
* 2.httpHead信息是一个MultiValueMap<String, String>
*/
public class HttpHeaders implements MultiValueMap<String, String>, Serializable {
/**
* The HTTP {@code Accept} header field name.
*/
public static final String ACCEPT = "Accept";
/**
* The HTTP {@code Accept-Charset} header field name.
*/
public static final String ACCEPT_CHARSET = "Accept-Charset";
}