Task manager (java)-CodePudding

Program must accept requests to add and remove tasks from the list through the server. After starting, server accepts connections in an infinite loop and reads from them a line containing json of the form:

{ "type": "ADD", "task": "Название задачи" }

where type is the type of operation (ADD or REMOVE) and task is the task itself. After processing the request, a list of all tasks should be displayed in the console. After connecting, my console gives null. What can be wrong?

Server class:

public class TodoServer {


public TodoServer(int port, Todos todos) {
    while (true) {
        try (ServerSocket serverSocket = new ServerSocket(port);
             Socket clientSocket = serverSocket.accept();
             PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
             BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()))) {

            System.out.println("New connection accepted");


            final String json = in.readLine();

            Gson gson = new Gson();
            String type = gson.fromJson("\"type\"", String.class);
            String task = gson.fromJson("\"task\"", String.class);
            if (type.equals("ADD")) {
                todos.addTask(task);
            } else if (type.equals("REMOVE")) {
                todos.removeTask(task);
            }
            System.out.println(todos.getAllTasks());
        } catch (IOException e) {
            System.out.println("Соединение разорвано");
        }
    }
}

public void start() throws IOException {
    int port = 8989;
    System.out.println("Starting server at "   port   "...");
   
}

}

Task class:

public class Todos {
static ArrayList <String> tasks = new ArrayList<>();


public void addTask(String task) {
    tasks.add(task);
    Collections.sort(tasks);
}

public void removeTask(String task) {
    tasks.remove(task);//...
}

public String getAllTasks() {
    return tasks.toString();
}

public ArrayList<String> getListTask() {
    return tasks;
}

}

The Main class which the server starts:

public class Main {

public static void main(String[] args) throws IOException {
    Todos todos = new Todos();
    TodoServer server = new TodoServer(8989, todos);
    server.start();
}

}

CodePudding user response：

From what you've shown here, your parsing and use of JSON is the issue. As a starting point, you read a String json but then do nothing with it.

You'll want to parse that value into an object, and then access values out of it (like you would a dictionary or map). How to do that with GSON should have plenty of documentation and examples readily available.

If you are using an IDE for development, I also recommend using this as a great opportunity for trying the debugger out - setting breakpoints, inspecting values, etc!

CodePudding user response：

It would be better to define a simple POJO to represent a task:

@Data
class MyTask {
    private String type;
    private String task;
}

Here @Data is a Lombok annotation which provides the boilerplate code of getters/setters/default constructor/toString/hashCode/equals.

Then the instance of such POJO is deserialized from JSON abd processed as needed:

final String json = in.readLine();

MyTask task = new Gson().fromJson(json, MyTask.class);

if ("ADD".equals(task.getType())) {
    todos.addTask(task.getTask());
} else if ("REMOVE".equals(task.getType())) {
    todos.removeTask(task.getTask());
}
System.out.println(todos.getAllTasks());