webServer

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;


public class WebServer {

    private static WebServer instance;
    private int port;
    private ServerSocket srvr;
    private Socket skt;
    @SuppressWarnings("unused")
    private HashMap<String, User> users;

    private WebServer() {
        this.port = 8080;
        this.srvr = null;
        this.skt = null;
        this.users = new HashMap<String, User>();
    }

    public static WebServer getInstance() {
        if(instance == null) { instance  = new WebServer(); }
        return instance;
    }

    public void run() throws IOException {
        this.srvr = new ServerSocket(this.port);

        while (true) {
            try {
                skt = srvr.accept();
                new WebServerThread(skt);
                skt = null;
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }

    public int getPort() {
        return port;
    }

    public void setPort(int port) {
        this.port = port;
    }

    public ServerSocket getSrvr() {
        return srvr;
    }

    public void setSrvr(ServerSocket srvr) {
        this.srvr = srvr;
    }

    public Socket getSkt() {
        return skt;
    }

    public void setSkt(Socket skt) {
        this.skt = skt;
    }

    public HashMap<String, User> getUsers() {
        return users;
    }

    public void setUsers(HashMap<String, User> users) {
        this.users = users;
    }

    public static void setInstance(WebServer instance) {
        WebServer.instance = instance;
    }
}

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.Socket;
import java.util.ArrayList;
import java.util.HashMap;

public class WebServerThread extends Thread {

    private final String HTTP200 = "HTTP/1.0 200 OK\r\n";
    private final String HTTP201 = "HTTP/1.0 201 Created\r\n";
    private final String HTTP204 = "HTTP/1.0 204 No Content\r\n";
    private final String HTTP400 = "HTTP/1.0 400 Bad Request\r\n";
    private final String HTTP404 = "HTTP/1.0 404 File not found\r\n";
    private final String HTTPCONTENTTYPE = "Content-type: text/html; charset=UTF-8\r\n";

    private Socket sock;
    private String method;
    private String resource;
    private String firstLine;
    private HashMap<String, String> header;
    private HashMap<String, String> params;

    public WebServerThread(Socket sock) {
        this.sock = sock;
        this.method = "";
        this.firstLine = null;
        this.header = new HashMap<>();
        this.params = new HashMap<>();

        try {
            start();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    public void run() {
        try {

            parseHttp(sock.getInputStream());
            if (this.resource != null) {
                if (this.resource.equals("")) {
                    this.resource = "index.html";
                }
                synchronized (WebServer.getInstance().getUsers()) {
                    sendResponse(sock.getOutputStream());
                }
            }
            sock.close();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    private void sendResponse(OutputStream outputStream) throws IOException {
        if (this.resource.equals("index.html")) {
            this.fileResponse(outputStream);
        } else if (this.resource.equals("reguser.html")) {
            this.fileResponse(outputStream);
        } else if (this.resource.equals("finduser.html")) {
            this.fileResponse(outputStream);
        } else if (this.resource.startsWith("finduser?")) {
            this.onHtmlGetFindUser(outputStream);
        } else if (this.resource.equals("remuser.html")) {
            this.fileResponse(outputStream);
        } else if (this.resource.equals("listusers?")) {
            this.onHtmlGetAllUsers(outputStream);
        } else if (this.resource.equals("reguser")) {
            this.onHtmlPostRegisterUser(outputStream);
        } else if (this.resource.equals("remuser")) {
            this.onHtmlPostRemoveUser(outputStream);
        }

    }

    private void onHtmlPostRemoveUser(OutputStream outputStream) {

        String response = "";
        PrintStream ps = new PrintStream(outputStream);
        User user = WebServer.getInstance().getUsers().get(params.get("username"));
        response += HTTP200  + "\r\n";
        response += "<html><head></head><body>";
        if (user == null) {
            response += "<p> User with that username doesn't exist. "
                    + "</p> <a href=\"index.html\"><button style=\"width:100px\">Home</button></a><br>";
            response += "</body></html>";
            ps.println(response);
            ps.flush();
            return;
        }
        WebServer.getInstance().getUsers().remove(user.getUsername());
        response += "<p> User deleted successfully. "
                + "</p> <a href=\"index.html\"><button style=\"width:100px\">Home</button></a><br>";
        response += "</body></html>";
        ps.println(response);
        ps.flush();
    }

    private void onHtmlGetAllUsers(OutputStream outputStream) {
        String response = "";
        PrintStream ps = new PrintStream(outputStream);

        response += HTTP200 + "\r\n";
        response += "<html><head>";
        response += "<style>table{border-collapse:collapse;}table,th,td{border:2px solid black;}"
                + ".row:nth-child(even){background:#dde;}"
                + ".row:nth-child(odd){background:white;}</style>";
        response += "</head><body>";
        response += "<fieldset><legend>Number of users is: <b>" + Integer.toString(WebServer.getInstance().getUsers().size()) + "</b></legend>";
        response += "<table style=\"border:1px solid red\">";
        response += "<tr class=\"row\"><th>eFirstname</th><th>Lastname</th><th>Username</th></tr>";
        for (String string : WebServer.getInstance().getUsers().keySet()) {
            response += "<tr class=\"row\">";
            User user = WebServer.getInstance().getUsers().get(string);
            response += "<td>" +  user.getFirstName() + "</td>";
            response += "<td>" +  user.getLastName() + "</td>";
            response += "<td>" +  user.getUsername() + "</td>";
            response += "</tr>";
        }

        response += "</table></fieldset></body></html>";
        ps.println(response);
        ps.flush();

    }

    private void onHtmlGetFindUser(OutputStream outputStream) {

        String response = "";
        PrintStream ps = new PrintStream(outputStream);
        try {
            System.out.println(this.resource);
            String line[] = this.resource.split("\\?");
            System.out.println(line[1]);
            String[] params = line[1].split("\\=");
            System.out.println(params[1]);
            User user = WebServer.getInstance().getUsers().get(params[1]);
            if (user != null) {
                response += HTTP200 + "\r\n";
                response += "<html><head></head><body>";
                response += "<p>User <b>" + user.getUsername() + "</b> found!</p>";
                response += "<p>Password: ";
                for (int i = 0; i < (user.getPassword().length()); i++) {
                    response += "*";
                }
                response += "</p>";
                response += "<p>First name: " + user.getFirstName() + "</p>";
                response += "<p>Last name: " + user.getLastName() + "</p>";
                response += "<p>" + user.getSex() + "</p>";
            } else {
                response += HTTP200 + "\r\n";
                response += "<html><head></head><body>";
                response += "<p>User <b>" + params[1] + "</b> not found!</p>";
            }
            response += "<a href=\"index.html\"><button style=\"width:100px\">Home</button></a><br>";
            response += "<a href=\"finduser.html\"><button style=\"width:100px\">Try again</button></a><br>";
            response += "</body></html>";
        } catch (Exception e) {
            response += HTTP400 + "\r\n";
            response += "<p>Invalid input data!</p>";
        }
        ps.print(response);
        ps.flush();
    }

    private void onHtmlPostRegisterUser(OutputStream outputStream) {
        String response = "";
        PrintStream ps = new PrintStream(outputStream);
        System.out.println("---");
        for (String s : this.params.keySet()) {
            System.out.println(s + " : " + this.params.get(s));
        }
        System.out.println("---");

        if (!(this.params.containsKey("username") && this.params.containsKey("password")
                && this.params.containsKey("name") && this.params.containsKey("lname")
                && this.params.containsKey("male"))) {
            return;
        }
        User user = WebServer.getInstance().getUsers().get(this.params.get("username"));
        if (user == null) {
            User newUser = new User();
            newUser.setFirstName(this.params.get("name"));
            newUser.setLastName(this.params.get("lname"));
            newUser.setUsername(this.params.get("username"));
            newUser.setPassword(this.params.get("password"));
            newUser.setSex(this.params.get("male"));
            WebServer.getInstance().getUsers().put(newUser.getUsername(), newUser);
            response += HTTP200 + "\r\n";
            response += "<html><head></head><body>";
            response += "<p>User <b>" + newUser.getUsername() + "</b> has successfully registred!</p>";
        } else {
            response += HTTP200 + "\r\n";
            response += "<html><head></head><body>";
            response += "<p>Registration failed! Username is already in use.</p>";
        }
        response += "<a href=\"reguser.html\"><button style=\"width:100px\">Try again</button></a>";
        response += "<a href=\"index.html\"><button style=\"width:100px\">Home</button></a><br>";
        response += "</body></html>";
        ps.println(response);
        ps.flush();
    }

    private void fileResponse(OutputStream os) throws IOException {
        PrintStream ps = new PrintStream(os);
        this.resource = this.resource.replace('/', File.separatorChar);
        File file = new File(this.resource);
        if (!file.exists()) {
            ps.print(HTTP404 + HTTPCONTENTTYPE + "\r\n" + "<b>404: File " + file.getName() + " not found!</b>");
            return;
        }
        ps.print(HTTP200 + "\r\n");
        FileInputStream fis = new FileInputStream(file);
        byte[] data = new byte[8192];
        int len;
        while ((len = fis.read(data)) != -1) {
            ps.write(data, 0, len);
        }

        fis.close();
        ps.flush();

    }

    private void parseHttp(InputStream is) throws IOException {
        BufferedReader dis = new BufferedReader(new InputStreamReader(is));
        System.out.println("=== HTTP REQ ===");
        this.firstLine = dis.readLine();
        System.out.println(this.firstLine);
        if (this.firstLine == null) {
            return;
        }
        String[] tokens = this.firstLine.split(" ");
        this.method = tokens[0];
        this.resource = tokens[1];
        this.resource = this.resource.substring(1);

        String s1;
        String s2[];
        while (!(s1 = dis.readLine()).equals("")) {
            System.out.println(s1);
            s2 = s1.split(": ");
            header.put(s2[0], s2[1]);
        }
        if (this.method.equals("POST")) {
            System.out.println("desilo se");
            this.extractPostParameters(dis);
        }
        System.out.println("================");

    }

    private void extractPostParameters(BufferedReader rdr) {
        try {
            String lengthStr = this.header.get("Content-Length");
            String contentType = this.header.get("Content-Type");
            if ((lengthStr != null) & (contentType != null)) {
                int len = 0;
                try {
                    len = Integer.parseInt(lengthStr);
                } catch (Exception e) {

                }

                if (len > 0 && contentType.equalsIgnoreCase("application/x-www-form-urlencoded")) {
                    String name, value, s1;
                    char buff[] = new char[len];
                    rdr.read(buff, 0, len);
                    s1 = new String(buff);
                    System.out.println("\n" + s1);
                    putInParamMap(s1);
                }
            }

        } catch (Exception e) {
            // TODO: handle exception
        }
    }

    private void putInParamMap(String s) {
        String[] tokens = s.split("&");
        for (String str : tokens) {
            int idx = str.indexOf("=");
            String pName = str.substring(0, idx).trim();
            String pValue = str.substring(idx + 1).trim();
            this.params.put(pName, pValue);
        }
    }
}


import java.io.IOException;

public class Main {

    public static void main(String[] args) throws IOException {
        WebServer.getInstance().run();
    }

}