是的，在uniapp中调用图像识别API时，需要在Java代码中编写请求签名，以下是详细的步骤和示例代码：

1、需要导入相关的依赖库，如commonscodec和commonsfileupload，可以在项目的pom.xml文件中添加以下依赖：

<dependencies>
    <dependency>
        <groupId>commonscodec</groupId>
        <artifactId>commonscodec</artifactId>
        <version>1.15</version>
    </dependency>
    <dependency>
        <groupId>commonsfileupload</groupId>
        <artifactId>commonsfileupload</artifactId>
        <version>1.4</version>
    </dependency>
</dependencies>

2、创建一个方法来生成请求签名，这个方法需要接收三个参数：accessKeyId（访问密钥ID），accessKeySecret（访问密钥）和expires（过期时间），返回值是一个字符串，表示生成的签名。

import org.apache.commons.codec.digest.HmacUtils;
import java.nio.charset.StandardCharsets;
import java.text.SimpleDateFormat;
import java.util.Date;
public String generateSignature(String accessKeyId, String accessKeySecret, int expires) {
    try {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd'T'HH:mm:ss");
        String dateStr = sdf.format(new Date(System.currentTimeMillis() + expires * 1000));
        String stringToSign = "GET&%2F&" + dateStr;
        byte[] signData = stringToSign.getBytes(StandardCharsets.UTF_8);
        byte[] keyData = accessKeySecret.getBytes(StandardCharsets.UTF_8);
        String signature = HmacUtils.hmacSha1Hex(keyData, signData);
        return "AWS4HMACSHA256 Credential=" + accessKeyId + "/" + dateStr + "/cnnorth1/image/v4/request, SignedHeaders=host, Signature=" + signature;
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
}

3、在调用图像识别API时，将生成的签名添加到请求头中，使用HttpURLConnection发送请求：

import java.net.HttpURLConnection;
import java.net.URL;
public void callImageRecognitionApi(String urlString, String accessKeyId, String accessKeySecret, int expires) {
    try {
        URL url = new URL(urlString);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        connection.setRequestProperty("Authorization", generateSignature(accessKeyId, accessKeySecret, expires));
        connection.connect();
        int responseCode = connection.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) {
            // 处理响应数据
        } else {
            // 处理错误情况
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
}

4、调用callImageRecognitionApi方法，传入图像识别API的URL、访问密钥ID、访问密钥和过期时间。