Develop Reference

Socket Server via Singleton with parameters from properties file

I am going to run Socket Server via Singleton Pattern because I have multiple threads, and every time I call it, I want to use the same socket server. This is SocketSingleton.java class :
public class SocketSingleton {
private static ServerSocket serverSocket = null;
private SocketSingleton() {}
public static synchronized ServerSocket getServerSocket() throws IOException {
PropertiesKey prop = new PropertiesKey();
if (serverSocket == null) {
serverSocket = new ServerSocket(prop.getSocketPort());
}
return serverSocket;
}
}
But I've noticed that I should get my few values from configuration.properties like SOCKET_PORT=2203
I can get the values from configuration with the code bellow
public class PropertiesAlgorithmImpl implements PropertiesAlgorithm {
private static Properties defaultProps = new Properties();
static {
try {
String propertiesDirectory = "src/main/resources/configuration.properties";
FileInputStream in = new FileInputStream(propertiesDirectory);
if (in == null) {
System.out.println("Sorry, unable to find " + propertiesDirectory);
}
defaultProps.load(in);
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}
public String getValuesFromProperties(String key) {
if (defaultProps.getProperty(key) != null) {
return defaultProps.getProperty(key);
}
return "Sorry, unable to find " + key ;
}
}
This is an enum of Socket Port.
public enum CONFIG { SOCKET_PORT}
public class PropertiesKey {
private PropertiesAlgorithm propertiesAlgorithm;
public int getSocketPort(){
propertiesAlgorithm = new PropertiesAlgorithmImpl();
return Integer.parseInt(propertiesAlgorithm.getValuesFromProperties(CONFIG.SOCKET_PORT.name()));
}
In the SocketSingleton class, I am calling socket port like this:
serverSocket = new ServerSocket(prop.getSocketPort());
What is the possible reason that I can't get the socket port parameters from configuration.properties?

I fixed the class bellow with input stream and it worked:
public class PropertiesAlgorithmImpl implements PropertiesAlgorithm {
private static final Logger logger = LoggerFactory.getLogger(PropertiesAlgorithmImpl.class);
private static Properties defaultProps = new Properties();
static {
String propertiesDirectory = "config.properties";
try (InputStream input = PropertiesAlgorithmImpl.class.getClassLoader().getResourceAsStream(propertiesDirectory)) {
if (input == null) {
logger.info("Sorry, unable to find " + propertiesDirectory);
}
defaultProps.load(input);
input.close();
} catch (Exception e) { logger.info(String.valueOf(e.getStackTrace())); }
}
public String getValuesFromProperties(String key) {
if (defaultProps.getProperty(key) != null) {
return defaultProps.getProperty(key);
}
logger.info("Sorry, unable to find " + key);
return "Sorry, unable to find " + key ;
}

MQTT client terminates without subscribing

I have set-up MQTT subscription as shown here:
package com.mqttW.demo;
import java.text.SimpleDateFormat;
import java.util.*;
import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import org.json.*;
public class WSync implements MqttCallback {
private String BROKER_URL = "";
private String PROTOCOL = "tcp://";
private String PORT = "1883";
private String TOPIC_ROOT_UNCNF = "/P/uncnf/";
private String TOPIC_ROOT_CNF = "/P/cnf/";
private DbOperations dbo = new DbOperations();
public void setBrokerUrl() {
this.BROKER_URL = PROTOCOL + System.getenv("BROKER_DNS") + ":" + PORT;
}
public String getBrokerUrl() {
return this.BROKER_URL;
}
public void publishPayload(String wName, String txnType, String payload) {
String clientId = wName + "-PUB";
String broker = this.getBrokerUrl();
String topic = TOPIC_ROOT_UNCNF + txnType + "/" + wName;
try {
MqttClient w = new MqttClient(broker, clientId);
w.connect();
MqttMessage message = new MqttMessage(payload.getBytes());
message.setQos(2);
w.publish(topic, message);
w.disconnect();
} catch (MqttException e) {
e.printStackTrace();
}
}
public void processTxns(String wName) {
this.setBrokerUrl();
String broker = this.getBrokerUrl();
String clientId = wName + "-SUB";
String topic = TOPIC_ROOT_CNF + wName + "/CR";
MemoryPersistence persistence = new MemoryPersistence();
try {
MqttConnectOptions c = new MqttConnectOptions();
c.setCleanSession(false);
MqttClient w = new MqttClient(broker, clientId, persistence);
w.connect(c);
w.setCallback(this);
w.subscribe(topic, 2);
System.out.println(w.getServerURI() + " " + w.getClientId() + " " + w.isConnected());
} catch (MqttException e) {
e.printStackTrace();
}
}
#Override
public void connectionLost(Throwable arg0) {
System.out.println("Connection lost at : " + new SimpleDateFormat("yyyy-MM-dd.HH:mm:ss").format(new java.util.Date()));
}
#Override
public void deliveryComplete(IMqttDeliveryToken arg0) {
// TODO Auto-generated method stub
}
#Override
public void messageArrived(String topic, MqttMessage message) throws Exception {
String s = new String(message.getPayload());
System.out.println(s);
}
}
The class with this method does implement MqttCallback. The System.out.println shows the broker URL, client ID and connected status (true) correctly.
So, what I am not getting is, why does the code terminate? Why is the subscription not set-up to listen for messages?

How to schedule a java code having messageArrived method of MqttCallback

I am new in MQTT world. I have written a code to subscribe a topic and get message from topic and store it in database. Now my problem is how to put this code on server so that it will keep receiving message infinitely. I am trying to create a scheduler but in that case i am Getting Persistence Already in Use error from MQTT. I cannot change the clientId every time it connect. It is a fixed one in my case. Is there any way to get the persistence object which is already connected for a particular clientId?
Please help. Thanks and advance.
Please Find the code subscribe topic and messageArrived method of mqqt to get message from topic
public class AppTest {
private MqttHandler handler;
public void doApp() {
// Read properties from the conf file
Properties props = MqttUtil.readProperties("MyData/app.conf");
String org = props.getProperty("org");
String id = props.getProperty("appid");
String authmethod = props.getProperty("key");
String authtoken = props.getProperty("token");
// isSSL property
String sslStr = props.getProperty("isSSL");
boolean isSSL = false;
if (sslStr.equals("T")) {
isSSL = true;
}
// Format: a:<orgid>:<app-id>
String clientId = "a:" + org + ":" + id;
String serverHost = org + MqttUtil.SERVER_SUFFIX;
handler = new AppMqttHandler();
handler.connect(serverHost, clientId, authmethod, authtoken, isSSL);
// Subscribe Device Events
// iot-2/type/<type-id>/id/<device-id>/evt/<event-id>/fmt/<format-id>
handler.subscribe("iot-2/type/" + MqttUtil.DEFAULT_DEVICE_TYPE
+ "/id/+/evt/" + MqttUtil.DEFAULT_EVENT_ID + "/fmt/json", 0);
}
/**
* This class implements as the application MqttHandler
*
*/
private class AppMqttHandler extends MqttHandler {
// Pattern to check whether the events comes from a device for an event
Pattern pattern = Pattern.compile("iot-2/type/"
+ MqttUtil.DEFAULT_DEVICE_TYPE + "/id/(.+)/evt/"
+ MqttUtil.DEFAULT_EVENT_ID + "/fmt/json");
DatabaseHelper dbHelper = new DatabaseHelper();
/**
* Once a subscribed message is received
*/
#Override
public void messageArrived(String topic, MqttMessage mqttMessage)
throws Exception {
super.messageArrived(topic, mqttMessage);
Matcher matcher = pattern.matcher(topic);
if (matcher.matches()) {
String payload = new String(mqttMessage.getPayload());
// Parse the payload in Json Format
JSONObject contObj = new JSONObject(payload);
System.out
.println("jsonObject arrived in AppTest : " + contObj);
// Call method to insert data in database
dbHelper.insertIntoDB(contObj);
}
}
}
Code to connect to client
public void connect(String serverHost, String clientId, String authmethod,
String authtoken, boolean isSSL) {
// check if client is already connected
if (!isMqttConnected()) {
String connectionUri = null;
//tcp://<org-id>.messaging.internetofthings.ibmcloud.com:1883
//ssl://<org-id>.messaging.internetofthings.ibmcloud.com:8883
if (isSSL) {
connectionUri = "ssl://" + serverHost + ":" + DEFAULT_SSL_PORT;
} else {
connectionUri = "tcp://" + serverHost + ":" + DEFAULT_TCP_PORT;
}
if (client != null) {
try {
client.disconnect();
} catch (MqttException e) {
e.printStackTrace();
}
client = null;
}
try {
client = new MqttClient(connectionUri, clientId);
} catch (MqttException e) {
e.printStackTrace();
}
client.setCallback(this);
// create MqttConnectOptions and set the clean session flag
MqttConnectOptions options = new MqttConnectOptions();
options.setCleanSession(false);
options.setUserName(authmethod);
options.setPassword(authtoken.toCharArray());
//If SSL is used, do not forget to use TLSv1.2
if (isSSL) {
java.util.Properties sslClientProps = new java.util.Properties();
sslClientProps.setProperty("com.ibm.ssl.protocol", "TLSv1.2");
options.setSSLProperties(sslClientProps);
}
try {
// connect
client.connect(options);
System.out.println("Connected to " + connectionUri);
} catch (MqttException e) {
e.printStackTrace();
}
}
}

ReadObject returns OptionalDataException

We are trying to send an object from an android Bluetooth client to a desktop Bluetooth server. We are trying to do this through the ObjectInputStream and ObjectOutput Stream. We are also very new to Bluetooth development, and have tried looking online for different examples and solutions.
Here is our code,
Android Code:
private static 1.5.0/docs/api/java/util/UUID.html">UUID generalUuid = 1.5.0/docs/api/java/util/UUID.html">UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
private static BluetoothSocket socket;
private static BluetoothSocket getBluetoothSocket(){
BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
mBluetoothAdapter.cancelDiscovery();
Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
// If there are paired devices
if (pairedDevices.size() > 0) {
// Loop through paired devices
for (BluetoothDevice device : pairedDevices) {
// Add the name and address to an array adapter to show in a ListView
if(device.getName().equalsIgnoreCase(("mint-0"))){
try {
return device.createRfcommSocketToServiceRecord(generalUuid);
} catch (1.5.0/docs/api/java/io/IOException.html">IOException e) {
return null;
}
}
}
}
return null;
}
public static boolean sendData(1.5.0/docs/api/java/lang/String.html">String first, 1.5.0/docs/api/java/lang/String.html">String last, int age){
socket = getBluetoothSocket();
try {
socket.connect();
} catch (1.5.0/docs/api/java/io/IOException.html">IOException e) {
// TODO Auto-generated catch block
socket = null;
}
if(socket != null){
try {
1.5.0/docs/api/java/io/ObjectOutputStream.html">ObjectOutputStream oos = new 1.5.0/docs/api/java/io/ObjectOutputStream.html">ObjectOutputStream(socket.getOutputStream());
oos.writeChars("X");
//send serializable object
personTest person = new personTest(first, last, age);
oos.writeObject(person);
oos.flush();
oos.close();
socket.close();
return true;
} catch (1.5.0/docs/api/java/io/IOException.html">IOException e) {
socket = null;
return false;
}
}else{
return false;
}
}
PC Code:
public class DataServer {
static final String serverUUID = "11111111111111111111111111111123";
public static void main(String[] args) throws IOException {
LocalDevice localDevice = LocalDevice.getLocalDevice();
localDevice.setDiscoverable(DiscoveryAgent.GIAC); // Advertising the service
System.out.println("Setting Discoverable");
String url = "btspp://localhost:" + serverUUID + ";name=BlueToothServer";
StreamConnectionNotifier server = (StreamConnectionNotifier) Connector.open(url);
System.out.println("Server: " + url);
StreamConnection connection = server.acceptAndOpen(); // Wait until client connects
System.out.println("Client Connected");
//=== At this point, two devices should be connected ===//
ObjectInputStream ois = new ObjectInputStream(connection.openInputStream());
personTest obj = null;
System.out.println("Waiting for Object");
//while(true){
try{
obj = (personTest) ois.readObject();
if(obj.getName() != "Gregg Miller"){
System.err.println("Name " + obj.getName() + " incorrect");
}
} catch(ClassNotFoundException cnfe){
System.err.println("cnfe "+cnfe.getMessage());
}
catch(InvalidClassException ice){
System.err.println("ice "+ice.getMessage());
}
catch(StreamCorruptedException sce){
System.err.println("sce "+sce.getMessage());
}
catch(IOException ioe){
System.err.println("ioe "+ioe.getMessage());
System.err.println(ioe.toString());
System.err.println("ODE Length: " +((OptionalDataException)ioe).length);
System.err.println("ODE EOF: " +((OptionalDataException)ioe).eof);
}
//}
System.out.println("Recieved, closing connection");
connection.close();
}
}
The output of the program after running both the android app and the desktop program are as followed:
ioe null
java.io.OptionalDataException
ODE Length: 2
ODE EOF: false
As requested, here is the PersonTest code:
package edit.rit.ce.whud;
import java.io.Serializable;
public class personTest extends Object implements Serializable {
private String firstName;
private String lastName;
private int age;
public personTest(String first, String last, int age){
this.firstName = first;
this.lastName = last;
this.age = age;
}
public String getName(){
return firstName +" "+ lastName;
}
public int getAge(){
return age;
}
}

Remove this:
oos.writeChars("X");
You're confusing the readObject() method at the other end. Or else read those chars at the other end.

using dbpedia spotlight in java or scala

Does anyone know where to find a little how to on using dbpedia spotlight in java or scala? Or could anyone explain how it's done? I can't find any information on this...

The DBpedia Spotlight wiki pages would be a good place to start.
And I believe the installation page has listed the most popular ways (using a jar, or set up a web service) to use the application.
It includes instructions on using the Java/Scala API with your own installation, or calling the Web Service.
There are some additional data needed to be downloaded to run your own server for full service, good time to make a coffee for yourself.

you need download dbpedia spotlight (jar file) after that u can use next two classes ( author pablomendes ) i only make some change .
public class db extends AnnotationClient {
//private final static String API_URL = "http://jodaiber.dyndns.org:2222/";
private static String API_URL = "http://spotlight.dbpedia.org:80/";
private static double CONFIDENCE = 0.0;
private static int SUPPORT = 0;
private static String powered_by ="non";
private static String spotter ="CoOccurrenceBasedSelector";//"LingPipeSpotter"=Annotate all spots
//AtLeastOneNounSelector"=No verbs and adjs.
//"CoOccurrenceBasedSelector" =No 'common words'
//"NESpotter"=Only Per.,Org.,Loc.
private static String disambiguator ="Default";//Default ;Occurrences=Occurrence-centric;Document=Document-centric
private static String showScores ="yes";
#SuppressWarnings("static-access")
public void configiration(double CONFIDENCE,int SUPPORT,
String powered_by,String spotter,String disambiguator,String showScores){
this.CONFIDENCE=CONFIDENCE;
this.SUPPORT=SUPPORT;
this.powered_by=powered_by;
this.spotter=spotter;
this.disambiguator=disambiguator;
this.showScores=showScores;
}
public List<DBpediaResource> extract(Text text) throws AnnotationException {
LOG.info("Querying API.");
String spotlightResponse;
try {
String Query=API_URL + "rest/annotate/?" +
"confidence=" + CONFIDENCE
+ "&support=" + SUPPORT
+ "&spotter=" + spotter
+ "&disambiguator=" + disambiguator
+ "&showScores=" + showScores
+ "&powered_by=" + powered_by
+ "&text=" + URLEncoder.encode(text.text(), "utf-8");
LOG.info(Query);
GetMethod getMethod = new GetMethod(Query);
getMethod.addRequestHeader(new Header("Accept", "application/json"));
spotlightResponse = request(getMethod);
} catch (UnsupportedEncodingException e) {
throw new AnnotationException("Could not encode text.", e);
}
assert spotlightResponse != null;
JSONObject resultJSON = null;
JSONArray entities = null;
try {
resultJSON = new JSONObject(spotlightResponse);
entities = resultJSON.getJSONArray("Resources");
} catch (JSONException e) {
//throw new AnnotationException("Received invalid response from DBpedia Spotlight API.");
}
LinkedList<DBpediaResource> resources = new LinkedList<DBpediaResource>();
if(entities!=null)
for(int i = 0; i < entities.length(); i++) {
try {
JSONObject entity = entities.getJSONObject(i);
resources.add(
new DBpediaResource(entity.getString("#URI"),
Integer.parseInt(entity.getString("#support"))));
} catch (JSONException e) {
LOG.error("JSON exception "+e);
}
}
return resources;
}
}
second class
/**
* #author pablomendes
*/
public abstract class AnnotationClient {
public Logger LOG = Logger.getLogger(this.getClass());
private List<String> RES = new ArrayList<String>();
// Create an instance of HttpClient.
private static HttpClient client = new HttpClient();
public List<String> getResu(){
return RES;
}
public String request(HttpMethod method) throws AnnotationException {
String response = null;
// Provide custom retry handler is necessary
method.getParams().setParameter(HttpMethodParams.RETRY_HANDLER,
new DefaultHttpMethodRetryHandler(3, false));
try {
// Execute the method.
int statusCode = client.executeMethod(method);
if (statusCode != HttpStatus.SC_OK) {
LOG.error("Method failed: " + method.getStatusLine());
}
// Read the response body.
byte[] responseBody = method.getResponseBody(); //TODO Going to buffer response body of large or unknown size. Using getResponseBodyAsStream instead is recommended.
// Deal with the response.
// Use caution: ensure correct character encoding and is not binary data
response = new String(responseBody);
} catch (HttpException e) {
LOG.error("Fatal protocol violation: " + e.getMessage());
throw new AnnotationException("Protocol error executing HTTP request.",e);
} catch (IOException e) {
LOG.error("Fatal transport error: " + e.getMessage());
LOG.error(method.getQueryString());
throw new AnnotationException("Transport error executing HTTP request.",e);
} finally {
// Release the connection.
method.releaseConnection();
}
return response;
}
protected static String readFileAsString(String filePath) throws java.io.IOException{
return readFileAsString(new File(filePath));
}
protected static String readFileAsString(File file) throws IOException {
byte[] buffer = new byte[(int) file.length()];
#SuppressWarnings("resource")
BufferedInputStream f = new BufferedInputStream(new FileInputStream(file));
f.read(buffer);
return new String(buffer);
}
static abstract class LineParser {
public abstract String parse(String s) throws ParseException;
static class ManualDatasetLineParser extends LineParser {
public String parse(String s) throws ParseException {
return s.trim();
}
}
static class OccTSVLineParser extends LineParser {
public String parse(String s) throws ParseException {
String result = s;
try {
result = s.trim().split("\t")[3];
} catch (ArrayIndexOutOfBoundsException e) {
throw new ParseException(e.getMessage(), 3);
}
return result;
}
}
}
public void saveExtractedEntitiesSet(String Question, LineParser parser, int restartFrom) throws Exception {
String text = Question;
int i=0;
//int correct =0 ; int error = 0;int sum = 0;
for (String snippet: text.split("\n")) {
String s = parser.parse(snippet);
if (s!= null && !s.equals("")) {
i++;
if (i<restartFrom) continue;
List<DBpediaResource> entities = new ArrayList<DBpediaResource>();
try {
entities = extract(new Text(snippet.replaceAll("\\s+"," ")));
System.out.println(entities.get(0).getFullUri());
} catch (AnnotationException e) {
// error++;
LOG.error(e);
e.printStackTrace();
}
for (DBpediaResource e: entities) {
RES.add(e.uri());
}
}
}
}
public abstract List<DBpediaResource> extract(Text text) throws AnnotationException;
public void evaluate(String Question) throws Exception {
evaluateManual(Question,0);
}
public void evaluateManual(String Question, int restartFrom) throws Exception {
saveExtractedEntitiesSet(Question,new LineParser.ManualDatasetLineParser(), restartFrom);
}
}
main()
public static void main(String[] args) throws Exception {
String Question ="Is the Amazon river longer than the Nile River?";
db c = new db ();
c.configiration(0.0, 0, "non", "CoOccurrenceBasedSelector", "Default", "yes");
System.out.println("resource : "+c.getResu());
}

I just add one little fix for your answer.
Your code is running, if you add the evaluate method call:
public static void main(String[] args) throws Exception {
String question = "Is the Amazon river longer than the Nile River?";
db c = new db ();
c.configiration(0.0, 0, "non", "CoOccurrenceBasedSelector", "Default", "yes");
c.evaluate(question);
System.out.println("resource : "+c.getResu());
}
Lamine

In the request method of the second class (AnnotationClient) in Adel's answer, the author Pablo Mendes hasn't finished
TODO Going to buffer response body of large or unknown size. Using getResponseBodyAsStream instead is recommended.
which is an annoying warning that needs to be removed by replacing
byte[] responseBody = method.getResponseBody(); //TODO Going to buffer response body of large or unknown size. Using getResponseBodyAsStream instead is recommended.
// Deal with the response.
// Use caution: ensure correct character encoding and is not binary data
response = new String(responseBody);
with
Reader in = new InputStreamReader(method.getResponseBodyAsStream(), "UTF-8");
StringWriter writer = new StringWriter();
org.apache.commons.io.IOUtils.copy(in, writer);
response = writer.toString();