使用Apache封装好来实现后端调用后端接口，要求header头中携带id，key，tenken，时间戳

在后端调用后端接口时，可以使用Apache HttpClient来进行封装。以下是一个示例代码：

import org.apache.http.HttpEntity;
import org.apache.http.HttpHeaders;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class BackendApiCaller {
    private static final String BASE_URL = "http://your.backend.api.url";
    private static final String API_PATH = "/api/your_api_path";
    private static final String ID = "your_id";
    private static final String KEY = "your_key";
    private static final String TOKEN = "your_token";

    public static void main(String[] args) throws Exception {
        HttpClient httpClient = HttpClientBuilder.create().build();
        HttpPost httpPost = new HttpPost(BASE_URL + API_PATH);

        // 设置请求头
        httpPost.setHeader(HttpHeaders.CONTENT_TYPE, "application/json;charset=UTF-8");
        httpPost.setHeader("id", ID);
        httpPost.setHeader("key", KEY);
        httpPost.setHeader("token", TOKEN);
        httpPost.setHeader("timestamp", getTimestamp());

        // 设置请求体
        String requestBody = "{\"param1\":\"value1\",\"param2\":\"value2\"}";
        httpPost.setEntity(new StringEntity(requestBody, StandardCharsets.UTF_8));

        // 发送请求
        HttpResponse response = httpClient.execute(httpPost);

        // 处理响应
        HttpEntity entity = response.getEntity();
        String responseBody = EntityUtils.toString(entity, StandardCharsets.UTF_8);
        System.out.println(responseBody);
    }

    private static String getTimestamp() throws NoSuchAlgorithmException {
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
        String timestamp = sdf.format(date);

        // 对时间戳进行 MD5 加密
        MessageDigest md = MessageDigest.getInstance("MD5");
        md.update(timestamp.getBytes(StandardCharsets.UTF_8));
        byte[] digest = md.digest();
        StringBuilder sb = new StringBuilder();
        for (byte b : digest) {
            sb.append(String.format("%02x", b & 0xff));
        }
        return sb.toString();
    }
}

在这个示例代码中，我们使用了Apache HttpClient来发送POST请求。在设置请求头时，我们设置了id、key、token和timestamp这四个字段。其中，timestamp需要在客户端生成，并对其进行MD5加密，以保证请求的唯一性。在设置请求体时，我们使用了一个JSON字符串作为示例。你需要根据具体的接口文档来设置实际的请求体。

需要注意的是，示例代码中的ID、KEY、TOKEN等字段应该根据实际情况进行替换。同时，你需要根据具体的接口文档来设置请求头中需要携带的字段。