I'm working on a program that takes in commands as string data and passes it to the correct handler, as defined by a HashMap
.
The code that passes the command to the correct handler is the following:
//This is run in its own thread, hence the run() method
@Override
public void run() {
try {
//Socket is a Socket object containing the client's connection
InputStreamReader is = new InputStreamReader(socket.getInputStream());
//MAX_MESSAGE_SIZE is an integer, specifically 1024
char[] data = new char[MAX_MESSAGE_SIZE];
is.read(data, 0, MAX_MESSAGE_SIZE);
String strData = new String(data);
//Split on UNIX or Windows type newline
String[] lines = strData.split("\\r?\\n");
//First verb determines the command
String command = (lines[0].split(": "))[0];
//Re-add the ": " because the HashMap will look for it
if (handlerMap.containsKey((command + ": "))) {
System.err.println("Got command: " + command);
AbstractHandler handler = handlerMap.get(command);
System.err.println("Passing connection + data to handler...");
handler.handleData(socket, lines);
System.err.println("Handler is done!");
} else {
System.err.println("Didn't understand command: " + command);
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
outputStream.writeBytes(Protocol.UNKNOWN_ERROR);
outputStream.flush();
socket.close();
}
} catch (IOException e) {
System.err.println("Caught IOException: " + e.getMessage());
}
}
The value part of the HashMap
is an object that implements the interface AbstractHandler
. AbstractHandler
defines the one method: handleData(Socket s, String[] lines)
. For reference, here is where the map is initialized:
public RequestManager(Socket socket) {
this.socket = socket;
handlerMap = new HashMap<>();
handlerMap.put(Protocol.USERNAME, new AuthenticationHandler());
//Set arg to true b/c it is a set request, not a change request
handlerMap.put(Protocol.SET_PASSWORD, new ChangePasswordHandler(true));
handlerMap.put(Protocol.CHANGE_PASSWORD, new ChangePasswordHandler());
handlerMap.put(Protocol.FORGOT_PASSWORD, new ForgotPasswordHandler());
}
and all of the handleData
methods in the objects just contain the following code:
@Override
public void handleData(Socket s, String[] lines) {
clientSocket = s; //clientSocket field in class
System.err.println("Made it into handler");
}
What's strange is after "Passing connection + data to handler" is shown, nothing happens. I don't see anything about getting into the handler, nor do I see exceptions or the message that the handler is done. What could cause this?
You test to see if a handler exists with
if (handlerMap.containsKey((command + ": "))) {
but you try and get a handler with
AbstractHandler handler = handlerMap.get(command);
So if it exists as for the key CommandName:
, you presumably won't get it with the key CommandName
. Therefore you'll have an unchecked NullPointerException
on the call handler.handleData(socket, lines);
and your runnable will die a horrid death.
It looks like you need to change either the first, or the second. Given you say you get to see it print "Passing connection + data to handler..." I think you need to change it to:
AbstractHandler handler = handlerMap.get(command + ": ");
A small stylistic change when you deal with maps would prevent this biting you now and in the future. Map.get
returns null
if the key is not found , so you can just do:
AbstractHandler handler = handlerMap.get(command + ": ");
if (handler != null) {
/* ... */
handler.handleData(socket, lines);
System.err.println("Handler is done!");
} else {
/* ... */
}
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