java - HttpClient setHeader 和 addHeader 有什么区别？

Question

使用 Apache HttpClient 版本时:

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.6</version>
</dependency>

setHeader 和 addHeader 有什么区别？

    httpPost.addHeader("AuthenticationKey",authenticationKey);
    httpPost.addHeader("Content-Type","application/json");

    httpPost.setHeader("Cache-Control", "no-cache"); // HTTP 1.1
    httpPost.setHeader("Pragma", "no-cache"); // HTTP 1.0
    httpPost.setHeader("X-Requested-With", "XMLHttpRequest"); // mimics a browser REST request

Answer 1

正如您可以从文档中读到的:

addHeader(String name, String value

Adds a header to this message. The header will be appended to the end of the list.

setHeader(String name, String value

Overwrites the first header with the same name. The new header will be appended to the end of the list, if no header with the given name can be found.