public class Client {
public static final long POLLING_PERIOD_MILLIS = 1000L;
public static final Logger CLIENT_LOGGER = new FileLogger("clientlog.txt");
private static final Logger logger = Log.create(Client.class);
private List<String> localHistory = new ArrayList<String>();
private String host;
private int port;
private boolean connected = false;
private Thread listenerThread;
private Thread messageSendingThread;
public Client(String host, Integer port) {
this.host = host;
this.port = port;
}
public void connect() {
URL url = null;
try {
url = new URL(Constants.PROTOCOL, host, port, Constants.CONTEXT_PATH);
url.openConnection(); // try connect to server
connected = true;
startListening();
startMessageSending();
} catch (MalformedURLException e) {
logger.error("Could not build URL to server", e);
throw new RuntimeException(e);
} catch (IOException e) {
logger.error(String.format("Could not connect to server on %s", url.toString()), e);
}
}
private HttpURLConnection prepareInputConnection(URL url) throws IOException {
HttpURLConnection connection = HttpURLConnection.class.cast(url.openConnection());
connection.setDoInput(true);
return connection;
}
private HttpURLConnection prepareOutputConnection() throws IOException {
URL url = new URL(Constants.PROTOCOL, host, port, Constants.CONTEXT_PATH);
HttpURLConnection connection = HttpURLConnection.class.cast(url.openConnection());
connection.setRequestMethod(Constants.REQUEST_METHOD_POST);
connection.setDoOutput(true);
return connection;
}
public void disconnect() {
// Thread#stop method is deprecated. The listeners threads stops when
// finish it's runnable action.
connected = false;
}
private void startListening() {
// if listener thread is alive and listening now, no need to recreate. Just reuse it.
if (listenerThread != null && listenerThread.isAlive()) {
return;
}
Runnable listeningAction =
() -> {
boolean running = true;
while (connected && running) {
List<String> list = getMessages();
localHistory.addAll(list);
try {
Thread.sleep(POLLING_PERIOD_MILLIS);
} catch (InterruptedException e) {
logger.error("The message listening thread was interrupted", e);
running = false;
}
}
};
listenerThread = new Thread(listeningAction);
listenerThread.start();
}
private void startMessageSending() {
// if listener thread is alive and listening now, no need to recreate. Just reuse it.
if (messageSendingThread != null && messageSendingThread.isAlive()) {
return;
}
Runnable messageSendingAction =
() -> {
Scanner scanner = new Scanner(System.in);
while (connected) {
String message = scanner.nextLine();
sendMessage(message);
}
};
messageSendingThread = new Thread(messageSendingAction);
messageSendingThread.start();
}
private void checkConnected() {
if (!connected) {
RuntimeException notConnectedError = new RuntimeException("No connection to server");
logger.error("No connection to server", notConnectedError);
throw notConnectedError;
}
}
public List<String> getMessages() {
CLIENT_LOGGER.info("start receiving messages");
checkConnected();
List<String> list = new ArrayList<>();
HttpURLConnection incomeConnection = null;
try {
CLIENT_LOGGER.info("send request for receive messages");
String query =
String.format(
"%s?%s=%s",
Constants.CONTEXT_PATH,
Constants.REQUEST_PARAM_TOKEN,
MessageHelper.buildToken(localHistory.size()));
URL url = new URL(Constants.PROTOCOL, host, port, query);
incomeConnection = prepareInputConnection(url);
CLIENT_LOGGER.info("response is received");
String response = MessageHelper.inputStreamToString(incomeConnection.getInputStream());
JSONObject jsonObject = MessageHelper.stringToJsonObject(response);
JSONArray jsonArray = (JSONArray) jsonObject.get("messages");
CLIENT_LOGGER.info("received " + jsonArray.size() + " messages");
for (Object o : jsonArray) {
logger.info(String.format("Message from server: %s", o));
CLIENT_LOGGER.info("message from server: " + o);
list.add(o.toString());
}
/** Here is an example how for cycle can be replaced with Java 8 Stream API */
// jsonArray.forEach(System.out::println);
// list = (List<String>)
// jsonArray.stream().map(Object::toString).collect(Collectors.toList());
} catch (ParseException e) {
logger.error("Could not parse message", e);
CLIENT_LOGGER.error("could not parse message", e);
} catch (ConnectException e) {
logger.error("Connection error. Disconnecting...", e);
CLIENT_LOGGER.error("connection error", e);
disconnect();
} catch (IOException e) {
logger.error("IOException occured while reading input message", e);
CLIENT_LOGGER.error("IOException occured while reading input message", e);
} finally {
if (incomeConnection != null) {
incomeConnection.disconnect();
}
}
CLIENT_LOGGER.info("stop receiving messages");
return list;
}
public void sendMessage(String message) {
checkConnected();
HttpURLConnection outcomeConnection = null;
try {
CLIENT_LOGGER.info("start sending message \"" + message + "\"");
outcomeConnection = prepareOutputConnection();
byte[] buffer = MessageHelper.buildSendMessageRequestBody(message).getBytes();
OutputStream outputStream = outcomeConnection.getOutputStream();
outputStream.write(buffer, 0, buffer.length);
outputStream.close();
outcomeConnection.getInputStream(); // to send data to server
CLIENT_LOGGER.info("message sent");
} catch (ConnectException e) {
logger.error("Connection error. Disconnecting...", e);
CLIENT_LOGGER.error("connection error", e);
disconnect();
} catch (IOException e) {
CLIENT_LOGGER.error("IOException", e);
logger.error("IOException occurred while sending message", e);
} finally {
if (outcomeConnection != null) {
outcomeConnection.disconnect();
}
CLIENT_LOGGER.info("stop sending message \"" + message + "\"");
}
}
}
public class ServerHandler implements HttpHandler {
private static final Logger logger = Log.create(ServerHandler.class);
private MessageStorage messageStorage = new InMemoryMessageStorage();
@Override
public void handle(HttpExchange httpExchange) throws IOException {
Response response;
try {
response = dispatch(httpExchange);
} catch (Throwable e) {
// WARNING! It's not a good practice to catch all exceptions via Throwable
// or Exception classes. But if you want to handle and you know
// how to handle them correctly, you may use such approach.
// Useful when you use thread pool and don't want to corrupt a thread
logger.error("An error occurred when dispatching request.", e);
response =
new Response(
Constants.RESPONSE_CODE_INTERNAL_SERVER_ERROR, "Error while dispatching message");
}
sendResponse(httpExchange, response);
}
private Response dispatch(HttpExchange httpExchange) {
if (Constants.REQUEST_METHOD_GET.equals(httpExchange.getRequestMethod())) {
return doGet(httpExchange);
} else if (Constants.REQUEST_METHOD_POST.equals(httpExchange.getRequestMethod())) {
return doPost(httpExchange);
} else if (Constants.REQUEST_METHOD_PUT.equals(httpExchange.getRequestMethod())) {
return doPut(httpExchange);
} else if (Constants.REQUEST_METHOD_DELETE.equals(httpExchange.getRequestMethod())) {
return doDelete(httpExchange);
} else if (Constants.REQUEST_METHOD_OPTIONS.equals(httpExchange.getRequestMethod())) {
return doOptions(httpExchange);
} else {
return new Response(
Constants.RESPONSE_CODE_METHOD_NOT_ALLOWED,
String.format("Unsupported http method %s", httpExchange.getRequestMethod()));
}
}
private Response doGet(HttpExchange httpExchange) {
String query = httpExchange.getRequestURI().getQuery();
if (query == null) {
return Response.badRequest("Absent query in request");
}
Map<String, String> map = queryToMap(query);
String token = map.get(Constants.REQUEST_PARAM_TOKEN);
if (StringUtils.isEmpty(token)) {
return Response.badRequest("Token query parameter is required");
}
try {
int index = MessageHelper.parseToken(token);
if (index > messageStorage.size()) {
return Response.badRequest(
String.format(
"Incorrect token in request: %s. Server does not have so many messages", token));
}
Portion portion = new Portion(index);
List<Message> messages = messageStorage.getPortion(portion);
String responseBody = MessageHelper.buildServerResponseBody(messages, messageStorage.size());
return Response.ok(responseBody);
} catch (InvalidTokenException e) {
return Response.badRequest(e.getMessage());
}
}
// +++++++
private Response doPost(HttpExchange httpExchange) {
try {
Message message = MessageHelper.getClientMessage(httpExchange.getRequestBody());
logger.info(String.format("Received new message from user: %s", message));
messageStorage.addMessage(message);
return Response.ok();
} catch (ParseException e) {
logger.error("Could not parse message.", e);
return new Response(Constants.RESPONSE_CODE_BAD_REQUEST, "Incorrect request body");
} catch (MessageExistException e) {
logger.error("Message with same id exist.", e);
return new Response(Constants.RESPONSE_CODE_BAD_REQUEST, "Message with same id exist");
}
}
// ++++++
private Response doPut(HttpExchange httpExchange) {
try {
JSONObject jsonObject =
stringToJsonObject(inputStreamToString(httpExchange.getRequestBody()));
Message message = new Message();
message.setId(((String) jsonObject.get(Constants.Message.FIELD_ID)));
message.setText(((String) jsonObject.get(Constants.Message.FIELD_TEXT)));
// System.out.println(((long)jsonObject.get(Constants.Message.FIELD_TIMESTAMP_MODIFIED)));
message.setTimestampModified(
((long) jsonObject.get(Constants.Message.FIELD_TIMESTAMP_MODIFIED)));
logger.info(String.format("Received updated message from user: %s", message));
if (messageStorage.updateMessage(message)) {
return Response.ok();
}
return Response.badRequest("This message does not exist");
} catch (ParseException e) {
logger.error("Could not parse message.", e);
return new Response(Constants.RESPONSE_CODE_BAD_REQUEST, "Incorrect request body");
}
}
private Response doDelete(HttpExchange httpExchange) {
String query = httpExchange.getRequestURI().getQuery();
if (query == null) {
return Response.badRequest("Absent query in request");
}
Map<String, String> map = queryToMap(query);
String messageId = map.get(Constants.REQUEST_PARAM_MESSAGE_ID);
if (StringUtils.isEmpty(messageId)) {
return Response.badRequest("Message id query parameter is required");
}
if (messageStorage.removeMessage(messageId)) {
return Response.ok();
}
return Response.badRequest("This message does not exist");
}
private Response doOptions(HttpExchange httpExchange) {
httpExchange
.getResponseHeaders()
.add(Constants.REQUEST_HEADER_ACCESS_CONTROL_METHODS, Constants.HEADER_VALUE_ALL_METHODS);
return Response.ok();
}
private void sendResponse(HttpExchange httpExchange, Response response) {
try (OutputStream os = httpExchange.getResponseBody()) {
byte[] bytes = response.getBody().getBytes();
Headers headers = httpExchange.getResponseHeaders();
headers.add(Constants.REQUEST_HEADER_ACCESS_CONTROL_ORIGIN, "*");
httpExchange.sendResponseHeaders(response.getStatusCode(), bytes.length);
os.write(bytes);
// there is no need to close stream manually
// as try-catch with auto-closable is used
/**
* {@see http://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html}
*/
} catch (IOException e) {
logger.error("Could not send response", e);
}
}
private Map<String, String> queryToMap(String query) {
Map<String, String> result = new HashMap<>();
for (String queryParam : query.split(Constants.REQUEST_PARAMS_DELIMITER)) {
String paramKeyValuePair[] = queryParam.split("=");
if (paramKeyValuePair.length > 1) {
result.put(paramKeyValuePair[0], paramKeyValuePair[1]);
} else {
result.put(paramKeyValuePair[0], "");
}
}
return result;
}
/**
* This method does absolutely the same as {@link ServerHandler#queryToMap(String)} one, but uses
* Java's 8 Stream API and lambda expressions
*
* <p>It's just as an example. Bu you can use it
*
* @param query the query to be parsed
* @return the map, containing parsed key-value pairs from request
*/
private Map<String, String> queryToMap2(String query) {
return Stream.of(query.split(Constants.REQUEST_PARAMS_DELIMITER))
.collect(
Collectors.toMap(
keyValuePair -> keyValuePair.split("=")[0],
keyValuePair -> keyValuePair.split("=")[1]));
}
}
public class InMemoryMessageStorage implements MessageStorage {
private static final String DEFAULT_PERSISTENCE_FILE = "messages.srg";
private static final Logger logger = Log.create(InMemoryMessageStorage.class);
private List<Message> messages;
public InMemoryMessageStorage() {
messages = new ArrayList<>();
loadHistory();
}
@Override
public synchronized List<Message> getPortion(Portion portion) {
int from = portion.getFromIndex();
if (from < 0) {
throw new IllegalArgumentException(
String.format("Portion from index %d can not be less then 0", from));
}
int to = portion.getToIndex();
if (to != -1 && to < portion.getFromIndex()) {
throw new IllegalArgumentException(
String.format("Porting last index %d can not be less then start index %d", to, from));
}
to = Math.max(to, messages.size());
return messages.subList(from, to);
}
@Override
public void addMessage(Message message) {
messages.add(message);
rewriteHistory();
}
@Override
public boolean updateMessage(Message message) {
for (int i = 0; i < messages.size(); i++) {
if (messages.get(i).getId().compareTo(message.getId()) == 0) {
Message newMessage = messages.get(i);
if (newMessage.isDeleted()) return false;
if (newMessage.isEdited()) {
newMessage.setWasEdited(true);
}
newMessage.setText(message.getText());
newMessage.setEdited(true);
messages.set(i, newMessage);
rewriteHistory();
return true;
}
}
return false;
}
@Override
public synchronized boolean removeMessage(String messageId) {
for (int i = 0; i < messages.size(); i++) {
if (messages.get(i).getId().compareTo(Long.parseLong(messageId)) == 0) {
Message newMessage = messages.get(i);
newMessage.setText("");
newMessage.setDeleted(true);
newMessage.setEdited(false);
newMessage.setWasEdited(false);
messages.set(i, newMessage);
rewriteHistory();
return true;
}
}
return false;
}
@Override
public int size() {
return messages.size();
}
private boolean rewriteHistory() {
try (Writer writer =
new OutputStreamWriter(new FileOutputStream(DEFAULT_PERSISTENCE_FILE), "UTF-8")) {
JSONArray array = MessageHelper.getJsonArrayOfMessages(messages);
writer.write(array.toString());
return true;
} catch (IOException e) {
logger.error("Could not parse message.", e);
return false;
}
}
private void loadHistory() {
StringBuilder jsonArrayString = new StringBuilder();
try (BufferedReader reader = new BufferedReader(new FileReader(DEFAULT_PERSISTENCE_FILE))) {
while (reader.ready()) {
jsonArrayString.append(reader.readLine());
}
} catch (IOException e) {
logger.error("Could not parse message.", e);
}
JSONArray jsonArray = new JSONArray();
if (jsonArrayString.length() == 0) {
return;
}
try {
jsonArray = (JSONArray) MessageHelper.getJsonParser().parse(jsonArrayString.toString());
} catch (ParseException e) {
logger.error("Could not parse message.", e);
}
for (int i = 0; i < jsonArray.size(); i++) {
JSONObject jsonObject = (JSONObject) jsonArray.get(i);
Message message = MessageHelper.jsonObjectToMessage(jsonObject);
messages.add(message);
}
}
}
public class MessageHelper {
public static final String MESSAGE_PART_ALL_MSG = "messages";
public static final String MESSAGE_PART_SINGLE_MSG = "message";
public static final String MESSAGE_PART_TOKEN = "token";
public static final String TOKEN_TEMPLATE = "TN%dEN";
public static final String TOKEN_FORMAT = "TN[0-9]{2,}EN";
private static final JSONParser jsonParser = new JSONParser();
private static final Logger logger = Log.create(MessageHelper.class);
/**
* Builds token based on amount of messages, which are already stored on server side or client
* side.
*
* <p>E.g. Client has 5 messages. It does not want to retrieve messages it already has. So, client
* passes 5 as argument to this method, and this method will return a token, which says to server:
* Just give me all messages, but skip first 5.
*
* <p>On the other hand, server passes amount of messages it has (size of messages collection).
* So, client can parse token and understand how many messages are on server side
*
* @param receivedMessagesCount amount of messages to skip.
* @return generated token
*/
public static String buildToken(int receivedMessagesCount) {
Integer stateCode = encodeIndex(receivedMessagesCount);
return String.format(TOKEN_TEMPLATE, stateCode);
}
/**
* Parses token and extract encoded amount of messages (typically - index)
*
* @param token the token to be parsed
* @return decoded amount messages (index)
*/
public static int parseToken(String token) {
if (!token.matches(TOKEN_FORMAT)) {
throw new InvalidTokenException("Incorrect format of token");
}
String encodedIndex = token.substring(2, token.length() - 2);
try {
int stateCode = Integer.valueOf(encodedIndex);
return decodeIndex(stateCode);
} catch (NumberFormatException e) {
logger.error("Could not parse token", e);
throw new InvalidTokenException("Invalid encoded value: " + encodedIndex);
}
}
private static int encodeIndex(int receivedMessagesCount) {
return receivedMessagesCount * 8 + 11;
}
private static int decodeIndex(int stateCode) {
return (stateCode - 11) / 8;
}
@SuppressWarnings(
"unchecked") // allows to suppress warning of unchecked parameter type for generics
public static String buildServerResponseBody(List<Message> messages, int lastPosition) {
JSONArray array = getJsonArrayOfMessages(messages);
JSONObject jsonObject = new JSONObject();
jsonObject.put(MESSAGE_PART_ALL_MSG, array);
jsonObject.put(MESSAGE_PART_TOKEN, buildToken(lastPosition));
return jsonObject.toJSONString();
}
private static JSONArray getJsonArrayOfMessages(List<Message> messages) {
// Java * approach
/*
List<JSONObject> jsonMessages = messages.stream()
.map(MessageHelper::messageToJSONObject)
.collect(Collectors.toList());
*/
List<JSONObject> jsonMessages = new LinkedList<>();
for (Message message : messages) {
jsonMessages.add(messageToJSONObject(message));
}
JSONArray array = new JSONArray();
array.addAll(jsonMessages);
return array;
}
@SuppressWarnings("unchecked")
public static String buildSendMessageRequestBody(String message) {
JSONObject jsonObject = new JSONObject();
jsonObject.put(MESSAGE_PART_SINGLE_MSG, message);
return jsonObject.toJSONString();
}
public static Message getClientMessage(InputStream inputStream) throws ParseException {
JSONObject jsonObject = stringToJsonObject(inputStreamToString(inputStream));
String id = ((String) jsonObject.get(Constants.Message.FIELD_ID));
String author = ((String) jsonObject.get(Constants.Message.FIELD_AUTHOR));
long timestamp = ((long) jsonObject.get(Constants.Message.FIELD_TIMESTAMP));
String text = ((String) jsonObject.get(Constants.Message.FIELD_TEXT));
boolean deleted = jsonObject.get(Constants.Message.FIELD_DELETED).equals("true");
Message message = new Message();
message.setId(id);
message.setAuthor(author);
message.setTimestamp(timestamp);
message.setText(text);
message.setDeleted(deleted);
return message;
}
public static JSONObject stringToJsonObject(String json) throws ParseException {
// The same as (JSONObject) jsonParser.parse(json.trim());
return JSONObject.class.cast(jsonParser.parse(json.trim()));
}
public static String inputStreamToString(InputStream in) {
byte[] buffer = new byte[1024];
int length = 0;
try (ByteArrayOutputStream outStream = new ByteArrayOutputStream()) {
while ((length = in.read(buffer)) != -1) {
outStream.write(buffer, 0, length);
}
return outStream.toString();
} catch (IOException e) {
logger.error("An error occurred while reading input stream", e);
throw new RuntimeException(e);
}
}
private static JSONObject messageToJSONObject(Message message) {
JSONObject jsonObject = new JSONObject();
jsonObject.put(Constants.Message.FIELD_ID, message.getId());
jsonObject.put(Constants.Message.FIELD_AUTHOR, message.getAuthor());
jsonObject.put(Constants.Message.FIELD_TIMESTAMP, message.getTimestamp());
jsonObject.put(Constants.Message.FIELD_TEXT, message.getText());
jsonObject.put(Constants.Message.FIELD_DELETED, message.isDeleted());
return jsonObject;
}
}
