httpPost.addHeader和httpPost.setHeader的区别是什么

`addHeader` 和 `setHeader` 都是用于向HTTP请求中添加头部信息的方法，但在使用上有一些区别：

1. **addHeader**：这个方法主要用于向请求头追加新的字段。如果请求头中已经有相同的键（header name），它会将新的值附加到原有值之后，用逗号分隔。例如：

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

如果之前已设置过该头，就会变成 "Content-Type: application/json, existing-value"。

2. **setHeader**：这个方法则会完全替换原有的相同名称的头。如果请求头里已经有了某个key，那么使用`setHeader`将会清除旧的值并添加新的。例如：

   httpPost.setHeader("Content-Type", "application/json");

这时候如果有之前的 "Content-Type"，会被直接覆盖为 "Content-Type: application/json"。

总结来说，如果你想要追加新的值而不改变已有值，应使用 `addHeader`；而如果你想替换某个头的值，应该使用 `setHeader`。不过现代很多库可能会提供兼容这两种用法的方法，允许你在某个头不存在时使用 `addHeader`，存在时使用 `setHeader` 的效果。

相关问题

优化这段代码@PostMapping("/login") @ResponseBody @PassToken public Object login(String username,String password) throws IOException { String url="http://42.177.95.222:9202/platform/yugang/task/getToken"; HttpClient client = HttpClients.createDefault(); //默认post请求 HttpPost post = new HttpPost(url); //拼接多参数 JSONObject json = new JSONObject(); json.put("username", "渔业协会"); json.put("password", "Yuye!@#qwe"); post.addHeader("Content-type", "application/json; charset=utf-8"); post.setHeader("Accept", "application/json"); post.setEntity(new StringEntity(json.toString(), Charset.forName("utf-8"))); HttpResponse httpResponse = client.execute(post); HttpEntity entity = httpResponse.getEntity(); String s = EntityUtils.toString(entity); JSONObject jo = JSONObject.parseObject(s); String token = jo.getJSONObject("data").getString("token"); System.out.println("dsadasdasdsadasd"+token); return verify(token); } public Object verify(String token) throws IOException { String url="http://42.177.95.222:9202/platform/yugang/task/verify"; HttpClient client = HttpClients.createDefault(); //默认post请求 HttpPost post = new HttpPost(url); //拼接多参数 JSONObject json = new JSONObject(); json.put("token",token); post.addHeader("Content-type", "application/json; charset=utf-8"); post.setHeader("Accept", "application/json"); post.setEntity(new StringEntity(json.toString(), Charset.forName("utf-8"))); HttpResponse httpResponse = client.execute(post); HttpEntity entity = httpResponse.getEntity(); String s = EntityUtils.toString(entity); JSONObject jo = JSONObject.parseObject(s); return jo; }

这段代码的优化点有以下几个：

1. 将重复的代码抽取成公共方法，避免代码冗余。
2. 使用连接池管理 HttpClient 的连接，提高连接的复用率和性能。
3. 使用 try-with-resources 语句关闭 HttpClient 和 HttpEntity 对象，避免资源泄漏。

下面是代码优化后的示例：

private static final String BASE_URL = "http://42.177.95.222:9202/platform/yugang/task";

private CloseableHttpClient httpClient = HttpClientBuilder.create()
        .setMaxConnTotal(200)
        .setMaxConnPerRoute(100)
        .build();

@PostMapping("/login")
@ResponseBody
@PassToken
public Object login(String username, String password) throws IOException {
    String token = getToken();
    System.out.println("dsadasdasdsadasd" + token);
    return verify(token);
}

private String getToken() throws IOException {
    String url = BASE_URL + "/getToken";
    HttpPost post = new HttpPost(url);
    post.addHeader("Content-type", "application/json; charset=utf-8");
    post.setHeader("Accept", "application/json");
    JSONObject json = new JSONObject();
    json.put("username", "渔业协会");
    json.put("password", "Yuye!@#qwe");
    post.setEntity(new StringEntity(json.toString(), Charset.forName("utf-8")));

    try (CloseableHttpResponse response = httpClient.execute(post)) {
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            String s = EntityUtils.toString(entity);
            JSONObject jo = JSONObject.parseObject(s);
            return jo.getJSONObject("data").getString("token");
        }
        return null;
    }
}

private JSONObject verify(String token) throws IOException {
    String url = BASE_URL + "/verify";
    HttpPost post = new HttpPost(url);
    post.addHeader("Content-type", "application/json; charset=utf-8");
    post.setHeader("Accept", "application/json");
    JSONObject json = new JSONObject();
    json.put("token", token);
    post.setEntity(new StringEntity(json.toString(), Charset.forName("utf-8")));

    try (CloseableHttpResponse response = httpClient.execute(post)) {
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            String s = EntityUtils.toString(entity);
            return JSONObject.parseObject(s);
        }
        return null;
    }
}

在优化后的代码中，我们将 HttpClient 对象的创建和关闭都放在了方法外部，使用连接池管理 HttpClient 的连接，提高连接的复用率和性能。同时，我们也将 getToken 和 verify 方法抽取出来，避免了代码冗余。最后，我们使用了 try-with-resources 语句来关闭 HttpClient 和 HttpEntity 对象，避免了资源泄漏。

import org.apache.http.client.config.RequestConfig; import org.apache.http.client.methods.HttpPost; import org.apache.http.entity.StringEntity; import org.apache.http.protocol.HTTP; import org.springframework.stereotype.Service; import org.springframework.util.DigestUtils; import java.nio.charset.StandardCharsets; import java.util.Map; /** * @author GaoWei * @date 2023/4/20 17:10 */ public class BaseEblService{ private static final String SIGN = "%sebl-api-method%sebl-appkey%sebl-timestamp%sebl-v%s%s"; private static final String URL_PARAMS = "?ebl-api-method=%s&ebl-appkey=%s&ebl-timestamp=%s&ebl-v=%s&ebl-sign=%s" + "&ebl-sign-method=%s&ebl-format=%s&ebl-customer-id=%s"; private HttpPost getHttpPost(String eblHost, String paraJsonStr, Map<String, String> header) { HttpPost httppost = new HttpPost(eblHost); RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(120000).build(); httppost.setConfig(requestConfig); httppost.addHeader(HTTP.CONTENT_TYPE, "application/json"); if (header != null && header.size() > 0) { for (String key : header.keySet()) { httppost.addHeader(key, header.get(key)); } } StringEntity str = new StringEntity(paraJsonStr, "UTF-8"); httppost.setEntity(str); return httppost; } public static void main(String[] args) { String appkey = "83285869"; String appsecret = "3d359cbfb787401689629ebe6754c497"; String signMethod = "MD5"; String format = "json"; String version = "1.0"; String timestamp = String.valueOf(System.currentTimeMillis() / 1000); String signStr = String.format(SIGN, appsecret, "ebl.freeapi.2023050010", appkey, timestamp, version, appsecret); String eblSign = DigestUtils.md5DigestAsHex(signStr.getBytes(StandardCharsets.UTF_8)); System.out.println(String.format(URL_PARAMS, "ebl.freeapi.2023050010", appkey, timestamp, version, eblSign, signMethod, format, "JFYG-JFSJZT")); } }

这段代码是用 Java 语言编写的一个基础的 EBL 服务类，主要包括了对 HTTP POST 请求的封装和签名算法的实现。其中，`getHttpPost` 方法用于构建 HTTP POST 请求，并设置请求头和请求参数；`main` 方法用于生成 EBL API 的签名，并输出完整的请求 URL。该代码中使用了 `org.apache.http` 和 `org.springframework.util` 两个库。