String realm = "<<your_client_host_url>>"
String authPrefix = "<<authPrefix>>
String httpMethod = "get"
//Append the query param in the url or else add as ApiList 
String signingUrl = "https://<<URL>>/api/v1/?param1=first&param2=123";
String certFileName = "certificates/ssc.alpha.example.com.p12";
String password = "<<passphrase>>";
String alias = "alpha";
String appId = "<<appId>>";
String secret = null;
//only needed for Content-Type: application/x-www-form-urlencoded, else null
ApiList formData = null;
String nonce = null;
String timestamp = null;


//optional for QueryParam - in-case not append the query parameters in the signingUrl
//Sring signingUrl = "https://<<tenant>>-pvt.i.api.gov.sg/api/v1"
ApiList queryParam = new ApiList();
queryParam.add("query1","value1");

//optional for formData
formData = new ApiList();
formData.add("param1", "data1");

//If queryParam and formData are both available, combine the list before submitting
formData.addAll(queryParam);

try {
    String signature = ApiSigning.getSignatureToken(authPrefix, authPrefix, httpMethod, signingUrl, appId, secret, formData, password, alias, certFileName, nonce, timestamp);
} catch (ApiUtilException e) {
    e.printStackTrace();
}

String signingUrl = "https://<<URL>>/api/v1/?param1=first&param2=123";

ApiList formData = new ApiList();
formData.add("param1", "data1");

String baseString;

try {
baseString = ApiSigning.getBaseString(
    "<<authPrefix>>",
    "HMACSHA256",
    "<<appId>>",
    signingUrl,
    "post",
    formData,
    "6584351262900708156",
    "1502184161702"
);

System.out.println(baseString);

} catch (ApiUtilException e) {
    e.printStackTrace();
}
                                      

String baseString = "GET&https://<<URL>>/api/v1/&ap=裕廊坊 心邻坊&<<authPrefix>>_app_id=<<appID>&<<authPrefix>>_nonce=2851111144329605674&<<authPrefix>>_signature_method=HMACSHA256&<<authPrefix>>_timestamp=1502163903712&<<authPrefix>>_version=1.0";
String secret = "<<appSecret>>";
String L1Sig;
		
try {
    L1Sig = ApiSigning.getHMACSignature(baseString, secret);
    System.out.println(L1Sig);

} catch (ApiUtilException e) {
    e.printStackTrace();
}

String baseString = "GET&https://<<URL>/api/v1/&ap=裕廊坊 心邻坊&<<authPrefix>>_app_id=<<appId>>&<<authPrefix>>_nonce=7231415196459608363&<<authPrefix>>_signature_method=SHA256withRSA&<<authPrefix>>_timestamp=1502164219425&<<authPrefix>>_version=1.0&oq=123&q=abc";
String alias = "alpha";
String password = "<<passphrase>>";
String keyStoreFileName = "certificates/ssc.alpha.example.com.p12";
String publicCertFileName = "certificates/ssc.alpha.example.com.cer";

try {
    
    PrivateKey privateKey = ApiSigning.getPrivateKeyFromKeyStore(keyStoreFileName, password, alias);
    
    String signature = ApiSigning.getRSASignature(baseString, privateKey);

    System.out.println(expectedSignature);
    System.out.println(signature);
    
    PublicKey publicKey = ApiSigning.getPublicKeyFromX509Certificate(publicCertFileName);
    
} catch (ApexUtilLibException e) {
    e.printStackTrace();
}

@Test
public void Http_Call_Test() throws ApiUtilException, IOException
{
	
	String httpMethod = "POST";
	//URL for actual HTTP API call
	String url = "https://tenant.api.gov.sg:443/api14021live/resource";
	//URL for passing as parameter for APEX Signature Token generation
	String signUrl = "https://tenant.e.api.gov.sg:443/api14021live/resource";
	String appId = "tenant-1X2w7NQPzjO2azDu904XI5AE";
	String secret = "s0m3s3cr3t";
	ApiList formData = new ApiList();
	formData.add("key1", "value1");
	formData.add("key2","value2");
	
	String authorizationToken = ApiSigning.getSignatureToken(
        realm
		, authPrefixL1
		, httpMethod
		, signUrl
		, appId
		, secret
		, formData
		, null
		, null
		, null
		, null
		, null
	);
	System.out.println("authorizationToken : "+authorizationToken);
	
	try {
		//ignore SSL
		SSLContext sslContext = SSLContext.getInstance("SSL");
		sslContext.init(null, getTrustManager(), new java.security.SecureRandom());
		HttpsURLConnection.setDefaultSSLSocketFactory(sslContext.getSocketFactory());
		
		HttpURLConnection con = (HttpURLConnection) new URL(url).openConnection();
		con.setDoOutput(true);
		con.setDoInput(true);
		con.setRequestMethod(httpMethod);
		con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");			
		con.setRequestProperty("charset", "utf-8");
		con.setRequestProperty("Authorization", authorizationToken);
		con.setUseCaches(false);
		con.setConnectTimeout(5000);
		con.setReadTimeout(5000);
		
		DataOutputStream out = new DataOutputStream(con.getOutputStream());
		ApiList formPostData = new ApiList();
		formPostData.add("key1",URLEncoder.encode("value1", "UTF-8"));
		formPostData.add("key2",URLEncoder.encode("value2", "UTF-8"));
		out.writeBytes(formPostData.toString(false));
		out.flush();
		out.close();
		System.out.println("Start http call ...");
		int status = -1;
		status = con.getResponseCode();
		System.out.println("HTTP Status:" + status);
		
		System.out.println("End http call ...");
		BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
		String inputLine;
		StringBuffer content = new StringBuffer();
		while ((inputLine = in.readLine()) != null) {
			content.append(inputLine);
		}
		
		System.out.println("Content:" + content);
		in.close();
		con.disconnect();
	}catch(Exception e){
		System.out.println("Error executing Http_Call_Test() : " + e);
	}
	//force to true to pass the test case
	assertTrue(true);
}