如何设置HttpClient请求的内容类型标头？

设置HttpClient请求的内容类型标头通常是为了确保服务器能够正确解析发送的数据。以下是使用不同编程语言和库进行设置的示例：

Java (使用Apache HttpClient)

import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;

public class HttpClientExample {
    public static void main(String[] args) throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost("http://example.com/api");
        
        // 设置内容类型标头
        httpPost.setHeader("Content-Type", "application/json");
        
        String json = "{\"key\":\"value\"}";
        StringEntity entity = new StringEntity(json);
        httpPost.setEntity(entity);
        
        try (CloseableHttpResponse response = httpClient.execute(httpPost)) {
            System.out.println(response.getStatusLine());
        }
    }
}

C# (使用HttpClient)

using System;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

public class HttpClientExample
{
    public static async Task Main(string[] args)
    {
        using (HttpClient client = new HttpClient())
        {
            var content = new StringContent("{\"key\":\"value\"}", Encoding.UTF8, "application/json");
            HttpResponseMessage response = await client.PostAsync("http://example.com/api", content);
            
            Console.WriteLine(response.StatusCode);
        }
    }
}

Python (使用requests库)

import requests

url = 'http://example.com/api'
headers = {'Content-Type': 'application/json'}
data = {'key': 'value'}

response = requests.post(url, headers=headers, json=data)
print(response.status_code)