车牌号OCR识别

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.security.MessageDigest;

/**
 * 车牌号OCR - Java 示例代码
 * 接口地址：https://api.shuxuntech.com/v1/plate/ocr
 *
 * 说明：本示例只使用 JDK 原生 API（java.net / java.security），不依赖任何第三方 jar 包，
 *      也不需要本项目的工具类，复制到本地即可编译运行：
 *          javac PlateOcrDemo.java
 *          java PlateOcrDemo
 */
public class PlateOcrDemo {

    /** 数勋分配的 appKey，请替换为您自己的 appKey */
    private static final String APP_KEY = "您的appKey";
    /** 数勋分配的 appSecret，请替换为您自己的 appSecret */
    private static final String APP_SECRET = "您的appSecret";
    /** 接口地址 */
    private static final String API_URL = "https://api.shuxuntech.com/v1/plate/ocr";
    /** 图片base64 */
    private static final String IMAGE = "";
    /** 图片url */
    private static final String IMG_URL = "";

    public static void main(String[] args) throws Exception {
        // 1、当前 unix 时间毫秒值，服务端要求与服务器时间相差不能超过 5 分钟
        String timestamp = String.valueOf(System.currentTimeMillis());

        // 2、签名：按顺序拼接 appKey + timestamp + appSecret 后做 sha256，得到小写十六进制字符串
        String sign = sha256Hex(APP_KEY + timestamp + APP_SECRET);

        // 3、业务参数，拼成表单内容
        String body = "image=" + urlEncode(IMAGE) + "&" + "imgUrl=" + urlEncode(IMG_URL);

        // 4、发起 POST 请求，appKey、timestamp、sign 放在请求头
        HttpURLConnection conn = (HttpURLConnection) new URL(API_URL).openConnection();
        conn.setRequestMethod("POST");
        conn.setDoOutput(true);
        conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");
        conn.setRequestProperty("appKey", APP_KEY);
        conn.setRequestProperty("timestamp", timestamp);
        conn.setRequestProperty("sign", sign);
        conn.setConnectTimeout(10000);
        conn.setReadTimeout(20000);
        conn.getOutputStream().write(body.getBytes("UTF-8"));

        int status = conn.getResponseCode();
        // 5、读取返回内容：报错时读错误流，避免只拿到一个异常看不到原因
        InputStream in = (status >= 200 && status < 300) ? conn.getInputStream() : conn.getErrorStream();
        String result = readAll(in);
        conn.disconnect();

        System.out.println("HTTP状态码=" + status);
        System.out.println("返回结果=" + result);
    }

    /**
     * sha256 加密，返回小写十六进制字符串
     * 服务端校验签名用的就是这个算法（小写十六进制）
     */
    private static String sha256Hex(String content) throws Exception {
        byte[] bytes = MessageDigest.getInstance("SHA-256").digest(content.getBytes("UTF-8"));
        StringBuilder sb = new StringBuilder(bytes.length * 2);
        for (byte b : bytes) {
            sb.append(Character.forDigit((b >> 4) & 0xF, 16));
            sb.append(Character.forDigit(b & 0xF, 16));
        }
        return sb.toString();
    }

    /** url 编码，中文参数需要编码 */
    private static String urlEncode(String value) throws Exception {
        return URLEncoder.encode(value, "UTF-8");
    }

    /** 读取输入流内容 */
    private static String readAll(InputStream in) throws Exception {
        if (in == null) {
            return "";
        }
        StringBuilder sb = new StringBuilder();
        BufferedReader reader = new BufferedReader(new InputStreamReader(in, "UTF-8"));
        try {
            String line;
            while ((line = reader.readLine()) != null) {
                sb.append(line);
            }
        } finally {
            reader.close();
        }
        return sb.toString();
    }
}