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POI got java.lang.ClassCastException but I am sending Object, not String
 

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  1. POI got java.lang.ClassCastException but I am sending Object, not String
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    <p>I am sending serialized object via sockets. Problem is when I send only one string (message) I got this error mentioned on title. So here is class that creates socket object:</p> <pre><code>package Pinger; import java.io.*; import java.util.Vector; public class ChatMessage implements Serializable { protected static final long serialVersionUID = 1112122200L; static final int WHOISIN = 0, MESSAGE = 1, LOGOUT = 2, JOB = 3; private int type,frequency,maxScans,NUMTHREADS,ttl; Vector &lt;String&gt; IPS; private String message; // constructor ChatMessage(int type, String message) { this.type = type; this.message = message; } ChatMessage (int type, int frequency, Vector &lt;String&gt; IPS, int maxScans, int NUMTHREADS, int ttl){ this.type=type; this.frequency=frequency; this.IPS=IPS; this.maxScans=maxScans; this.NUMTHREADS=NUMTHREADS; this.ttl=ttl; } // getters . . . } </code></pre> <p>This class creazes serializable object that will be send over socket. Problem is when I am sending string message (that string is passed to ChatMessage class) I got error that java cannot cast from String to ChatMessage. Also I will give you Client and ClientGUI class to provide you with all you need to understand my code. I really don't know where is error. Can you guys help me with that? Best regards.</p> <pre><code>package Pinger; import java.net.*; import java.io.*; import java.util.*; public class Client { // for I/O private ObjectInputStream sInput; // to read from the socket private ObjectOutputStream sOutput; // to write on the socket private Socket socket; // if I use a GUI or not private ClientGUI cg; // the server, the port and the username private String server, username; private int port; /* * Constructor called by console mode * server: the server address * port: the port number * username: the username */ Client(String server, int port, String username) { // which calls the common constructor with the GUI set to null this(server, port, username, null); } /* * Constructor call when used from a GUI * in console mode the ClienGUI parameter is null */ Client(String server, int port, String username, ClientGUI cg) { this.server = server; this.port = port; this.username = username; // save if we are in GUI mode or not this.cg = cg; } /* * To start the dialog */ public boolean start() { // try to connect to the server try { socket = new Socket(server, port); } // if it failed not much I can so catch(Exception ec) { display("Error connecting to server:" + ec); return false; } String msg = "Connection accepted " + socket.getInetAddress() + ":" + socket.getPort(); display(msg); /* Creating both Data Stream */ try { sInput = new ObjectInputStream(socket.getInputStream()); sOutput = new ObjectOutputStream(socket.getOutputStream()); } catch (IOException eIO) { display("Exception creating new Input/output Streams: " + eIO); return false; } new ListenFromServer().start(); try { sOutput.writeObject(username); } catch (IOException eIO) { display("Exception doing login : " + eIO); disconnect(); return false; } // success we inform the caller that it worked return true; } /* * To send a message to the console or the GUI */ private void display(String msg) { if(cg == null) System.out.println(msg); // println in console mode else cg.append(msg + "\n"); // append to the ClientGUI JTextArea (or whatever) } /* * To send a message to the server */ void sendMessage(ChatMessage msg) { try { System.out.println(msg); sOutput.writeObject(msg); } catch(IOException e) { display("Exception writing to server: " + e); } } /* * When something goes wrong * Close the Input/Output streams and disconnect not much to do in the catch clause */ private void disconnect() { try { if(sInput != null) sInput.close(); } catch(Exception e) {} // not much else I can do try { if(sOutput != null) sOutput.close(); } catch(Exception e) {} // not much else I can do try{ if(socket != null) socket.close(); } catch(Exception e) {} // not much else I can do // inform the GUI if(cg != null) cg.connectionFailed(); } class ListenFromServer extends Thread { public void run() { while(true) { try { ChatMessage msg = (ChatMessage) sInput.readObject(); //if (nesto instanceof String) //msg = (String) sInput.readObject(); //} // if console mode print the message and add back the prompt if(cg == null) { System.out.println(msg.getMessage()); System.out.print("&gt; "); } else { cg.append(msg.getMessage()); } } catch(IOException e) { display("Server has close the connection: " + e); if(cg != null) cg.connectionFailed(); break; } // can't happen with a String object but need the catch anyhow catch(ClassNotFoundException e2) { } } } } } </code></pre> <p>Also here is GUI class for class client:</p> <pre><code>package Pinger; import javax.swing.*; import java.awt.*; import java.awt.event.*; import java.net.InetAddress; import java.net.UnknownHostException; /* * The Client with its GUI */ public class ClientGUI extends JFrame implements ActionListener { private static final long serialVersionUID = 1L; // will first hold "Username:", later on "Enter message" private JLabel label; // to hold the Username and later on the messages private JTextField tf; // to hold the server address an the port number private JTextField tfServer, tfPort; // to Logout and get the list of the users private JButton login, logout, whoIsIn; // for the chat room private JTextArea ta; // if it is for connection private boolean connected; // the Client object private Client client; // the default port number private int defaultPort; private String defaultHost; InetAddress ComputerIP; // Constructor connection receiving a socket number ClientGUI(String host, int port) throws UnknownHostException { super("Chat Client"); defaultPort = port; defaultHost = host; // The NorthPanel with: JPanel northPanel = new JPanel(new GridLayout(3,1)); // the server name anmd the port number JPanel serverAndPort = new JPanel(new GridLayout(1,5, 1, 3)); // the two JTextField with default value for server address and port number tfServer = new JTextField(host); tfPort = new JTextField("" + port); tfPort.setHorizontalAlignment(SwingConstants.RIGHT); serverAndPort.add(new JLabel("Server Address: ")); serverAndPort.add(tfServer); serverAndPort.add(new JLabel("Port Number: ")); serverAndPort.add(tfPort); serverAndPort.add(new JLabel("")); // adds the Server an port field to the GUI northPanel.add(serverAndPort); // the Label and the TextField ComputerIP = InetAddress.getLocalHost(); label = new JLabel("Enter your username below", SwingConstants.CENTER); northPanel.add(label); tf = new JTextField(ComputerIP.toString()); tf.setBackground(Color.WHITE); northPanel.add(tf); add(northPanel, BorderLayout.NORTH); // The CenterPanel which is the chat room ta = new JTextArea("Clients logs\n", 80, 80); JPanel centerPanel = new JPanel(new GridLayout(1,1)); centerPanel.add(new JScrollPane(ta)); ta.setEditable(false); add(centerPanel, BorderLayout.CENTER); // the 3 buttons login = new JButton("Login"); login.addActionListener(this); logout = new JButton("Logout"); logout.addActionListener(this); logout.setEnabled(false); // you have to login before being able to logout whoIsIn = new JButton("Who is in"); whoIsIn.addActionListener(this); whoIsIn.setEnabled(false); // you have to login before being able to Who is in JPanel southPanel = new JPanel(); southPanel.add(login); southPanel.add(logout); southPanel.add(whoIsIn); add(southPanel, BorderLayout.SOUTH); setDefaultCloseOperation(EXIT_ON_CLOSE); setSize(600, 600); setVisible(true); tf.requestFocus(); } // called by the Client to append text in the TextArea void append(String str) { ta.append(str); ta.setCaretPosition(ta.getText().length() - 1); } // called by the GUI is the connection failed // we reset our buttons, label, textfield void connectionFailed() { login.setEnabled(true); logout.setEnabled(false); whoIsIn.setEnabled(false); InetAddress localIP = null; label.setText("Enter your username below"); try { localIP=InetAddress.getLocalHost(); } catch (UnknownHostException e) { // TODO Auto-generated catch block e.printStackTrace(); } tf.setText(localIP.getHostAddress().toString()); // reset port number and host name as a construction time tfPort.setText("" + defaultPort); tfServer.setText(defaultHost); // let the user change them tfServer.setEditable(false); tfPort.setEditable(false); // don't react to a &lt;CR&gt; after the username tf.removeActionListener(this); connected = false; } /* * Button or JTextField clicked */ public void actionPerformed(ActionEvent e) { Object o = e.getSource(); // if it is the Logout button if(o == logout) { client.sendMessage(new ChatMessage(ChatMessage.LOGOUT, "")); return; } // if it the who is in button if(o == whoIsIn) { client.sendMessage(new ChatMessage(ChatMessage.WHOISIN, "")); return; } // ok it is coming from the JTextField if(connected) { // just have to send the message client.sendMessage(new ChatMessage(ChatMessage.MESSAGE, tf.getText())); tf.setText(""); return; } if(o == login) { // ok it is a connection request String username = tf.getText().trim(); // empty username ignore it if(username.length() == 0) return; // empty serverAddress ignore it String server = tfServer.getText().trim(); if(server.length() == 0) return; // empty or invalid port numer, ignore it String portNumber = tfPort.getText().trim(); if(portNumber.length() == 0) return; int port = 0; try { port = Integer.parseInt(portNumber); } catch(Exception en) { return; // nothing I can do if port number is not valid } // try creating a new Client with GUI client = new Client(server, port, username, this); // test if we can start the Client if(!client.start()) return; tf.setText(""); label.setText("Enter your message below"); connected = true; // disable login button login.setEnabled(false); // enable the 2 buttons logout.setEnabled(true); whoIsIn.setEnabled(true); // disable the Server and Port JTextField tfServer.setEditable(false); tfPort.setEditable(false); // Action listener for when the user enter a message tf.addActionListener(this); } } // to start the whole thing the server public static void main(String[] args) throws UnknownHostException { new ClientGUI("localhost", 6000); } } </code></pre> <p>EDIT 1: Added expection stacktrace</p> <pre><code>Exception in thread "Thread-2" java.lang.ClassCastException: java.lang.String cannot be cast to Pinger.ChatMessage at Pinger.Client$ListenFromServer.run(Client.java:143) </code></pre>
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      1. POI got java.lang.ClassCastException but I am sending Object, not String
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    1. COplease post exception stacktrace
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    2. COAdded exception stacktrace. Thank your for letting me know.
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    3. COSo you are sending a `String` and trying to read it as a `ChatMessage`. Too localized.
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      1. USuser207421
 

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