在AWS的HTTP Post示例中，签名密钥是指用于计算签名的密钥，它由Access Key和Secret Key组成。

以下是一个示例代码，展示了如何使用AWS SDK for Java来进行HTTP Post请求并计算签名：

import com.amazonaws.DefaultRequest;
import com.amazonaws.Request;
import com.amazonaws.auth.AWS4Signer;
import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.AWSCredentialsProvider;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.http.HttpMethodName;
import com.amazonaws.services.s3.AmazonS3Client;

import java.net.URI;
import java.net.URISyntaxException;

public class AWSSigningExample {
    public static void main(String[] args) throws URISyntaxException {
        // 请替换为您的Access Key和Secret Key
        String accessKey = "YOUR_ACCESS_KEY";
        String secretKey = "YOUR_SECRET_KEY";

        // 构建AWS4签名
        AWS4Signer signer = new AWS4Signer();
        signer.setServiceName("s3");
        signer.setRegionName("us-west-2");

        // 构建请求
        Request request = new DefaultRequest<>("s3");
        request.setEndpoint(new URI("https://s3.amazonaws.com/bucket-name"));
        request.setHttpMethod(HttpMethodName.POST);
        // 设置其他请求参数

        // 计算签名
        AWSCredentials credentials = new BasicAWSCredentials(accessKey, secretKey);
        AWSCredentialsProvider credentialsProvider = new StaticCredentialsProvider(credentials);
        signer.sign(request, credentialsProvider.getCredentials());

        // 获取签名信息
        String authorizationHeader = request.getHeaders().get("Authorization");
        System.out.println("Authorization Header: " + authorizationHeader);
    }
}

在上述示例中，您需要将"YOUR_ACCESS_KEY"和"YOUR_SECRET_KEY"替换为您的Access Key和Secret Key。

请注意，这只是一个示例，您需要根据您的具体情况进行适当的修改。此外，您还需要确保已正确配置AWS SDK和依赖项。