java httpclient post工具类

### Java HttpClient POST 请求工具类实现

为了实现一个通用的 `HttpClient` 工具类来执行 HTTP POST 请求，可以基于 Apache HttpComponents 库。下面是一个完整的工具类示例：

#### Maven依赖配置
首先，在项目的pom.xml文件中加入必要的Maven依赖项：

<dependencies>
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.5.13</version>
    </dependency>
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpmime</artifactId>
        <version>4.5.13</version>
    </dependency>
</dependencies>

#### HttpClientUtil.java - 工具类定义
接下来是具体的工具类代码实现:

import org.apache.http.HttpResponse;
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;
import org.apache.http.util.EntityUtils;

public class HttpClientUtil {

    public static String doPost(String url, String json) throws Exception {
        // 创建默认的httpClient实例.
        try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
            // 创建httppost
            HttpPost httppost = new HttpPost(url);
            
            // 设置请求头信息
            httppost.addHeader("Content-Type", "application/json");
            
            // 构建消息实体
            StringEntity entity = new StringEntity(json, "UTF-8");
            entity.setContentEncoding("UTF-8");
            entity.setContentType("application/json");

            // 将请求实体设置到httpPost对象中
            httppost.setEntity(entity);

            // 执行post请求操作
            HttpResponse response = httpclient.execute(httppost);
            int statusCode = response.getStatusLine().getStatusCode();
            if (statusCode != 200 && statusCode != 201) {
                throw new RuntimeException("Failed with status code: " + statusCode);
            }

            // 获取响应体内容
            String result = EntityUtils.toString(response.getEntity(), "utf-8");
            return result;
        }
    }
}

此段代码展示了如何利用Apache HttpClient库发起HTTP POST请求，并处理JSON格式的数据传输[^5]。