import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.*;
public class SHA512Utils {

public static final String ENCODE = "UTF-8";

/**
 * compute the SHA hash of the message and sign it.
 *
 * @param signParams signature parameters
 * @param key     secret
 * @return
 */
public static String SHAEncrypt(TreeMap<String, String> signParams, String key) {
    signParams.remove("sign");
    StringBuffer sb = new StringBuffer();
    Set es = signParams.entrySet();
    Iterator it = es.iterator();
    while (it.hasNext()) {
        Map.Entry entry = (Map.Entry) it.next();
        String k = (String) entry.getKey();
        String v = (String) entry.getValue();
        if (null != v && !"".equals(v) && !"sign".equals(k)
                && !"key".equals(k)) {
            sb.append(k + "=" + v + "&");
        }
    }
    sb.append("key=" + key);
    return encrypt(sb.toString(), ENCODE).toUpperCase();
}

public static String encrypt(String aValue, String encoding) {
    aValue = aValue.trim();
    byte value[];
    try {
        value = aValue.getBytes(encoding);
    } catch (UnsupportedEncodingException e) {
        value = aValue.getBytes();
    }
    MessageDigest md = null;
    try {
        md = MessageDigest.getInstance("SHA-512");
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
        return null;
    }
    return toHex(md.digest(value));
}

public static String toHex(byte input[]) {
    if (input == null)
        return null;
    StringBuffer output = new StringBuffer(input.length * 2);
    for (int i = 0; i < input.length; i++) {
        int current = input[i] & 0xff;
        if (current < 16)
            output.append("0");
        output.append(Integer.toString(current, 16));
    }
    return output.toString();
}

/**
 * verify signature
 *
 * @param signParams sign parameters
 * @param key        secret
 * @return
 */
public static boolean verifySHA(TreeMap<String, String> signParams, String key) {
    String verifySign = signParams.get("sign");
    String sign = SHAEncrypt(signParams, key);
    if (sign.equalsIgnoreCase(verifySign)) {
        return true;
    }
    return false;
}
}

    import java.util.Map;
    import com.alibaba.fastjson.JSONObject;

    public class SignTest {
        public static void main(String[] args) {
            String jsonData="{\n" +
                                " \"appId\": \"TEST000001\",\n" +
                                " \"sign\": \"TEST000001\",\n" +
                                " \"merchantOrderNo\": \"11126\"\n" +
                                "}\n";
    //Sign the data
    TreeMap resultMap=JSONObject.parseObject(jsonData, TreeMap.class);
    String result=SHA512Utils.SHAEncrypt(resultMap,"9999");
    System.out.println(result);

    //Verify the data,true=verify success
    resultMap.put("sign","95960053CC577FCAFC272410D5F70094DD0986F6C3266DB7D00D0B37A7CB12F6607125143987143EE168DA052C0A1FD436A0E14DBA57584CC977F82823318BDC");
    System.out.println(SHA512Utils.verifySHA(resultMap,"9999"));
        }
    }