我构建了一个 Java 服务器程序，它是出勤跟踪器应用程序的一部分。它接收来自客户端应用程序的命令，并执行连接到我们设置的数据库的服务器功能。问题是，一旦我们启动程序，它会在 session 开始时自动向客户端发送两个 U+FFFD 字符(带有问号符号的菱形)，从而破坏客户端代码，并在客户端返回错误。我无法弄清楚代码中发生这种情况的位置，因为打印到命令行的内容就是传递给客户端的内容。我什至不知道从哪里开始寻找。这是主文件的代码，如果需要，我会将整个项目上传到 Github 上。我知道有很多代码需要查看，但如果有人能够立即发现问题，我会很高兴。谢谢您的帮助!
Github:https://github.com/aepries/stacServ.git
package stacserv;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.ObjectOutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.HashMap;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import java.text.Normalizer;
public class StacServ {
/**
* @param args the command line arguments
*/
public static JFrame mainFrame = null;
public static JTextArea chatText = null;
public static StringBuffer toAppend = new StringBuffer("");
public static void initGUI(){
JPanel chatPane = new JPanel(new BorderLayout());
chatText = new JTextArea(20, 20);
chatText.setLineWrap(true);
chatText.setForeground(Color.blue);
chatText.setFont(chatText.getFont().deriveFont(20f));
JScrollPane chatTextPane = new JScrollPane(chatText,
JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
chatPane.add(chatTextPane, BorderLayout.CENTER);
chatPane.setPreferredSize(new Dimension(800, 400));
// Set up the main pane
JPanel mainPane = new JPanel(new BorderLayout());
mainPane.add(chatPane, BorderLayout.CENTER);
// Set up the main frame
mainFrame = new JFrame("Client Messages");
mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainFrame.setContentPane(mainPane);
mainFrame.setSize(mainFrame.getPreferredSize());
mainFrame.setLocation(300, 300);
mainFrame.pack();
mainFrame.setVisible(true);
}
public static void main(String[] args) throws Exception {
initGUI();
ServerSocket m_ServerSocket = new ServerSocket(1025);
int id = 0;
StacServ.chatText.append("Server is now running and listening on port 1025 " + "\n");
while (true) {
Socket clientSocket = m_ServerSocket.accept();
ClientServiceThread cliThread = new ClientServiceThread(clientSocket, id++);
cliThread.start();
}
}
}
class ClientServiceThread extends Thread {
Socket clientSocket;
int clientID = -1;
String userName = null;
boolean running = true;
private MySQLAccess dbconnection;
HashMap<Socket, Integer> connections = new HashMap<Socket, Integer>();
public ArrayList<ClassData> queryResult = new ArrayList<ClassData>();
StringBuilder sb = new StringBuilder();
String commandName = null;
String clientCommand = null;
String restofString = null;
String[] tokens = new String[2];
ClientServiceThread(Socket s, Integer i) {
clientSocket = s;
clientID = i;
connections.put(s, i);
StacServ.chatText.append("Current Connections" + "\n");
for(HashMap.Entry entry: connections.entrySet()){
StacServ.chatText.append(entry.getKey() + ", " + entry.getValue() + "\n");
}
}
@Override
public void run() {
try
{
dbconnection = new MySQLAccess();
dbconnection.connect("138.86.104.164","STACDB","SEClass","BearsRock");
} catch (Exception e) {
//System.out.println(e);
//e.printStackTrace();
}
System.out.println("Accepted Client : ID - " + clientID + " : Address - "
+ clientSocket.getInetAddress().getHostName());
StacServ.chatText.append("Accepted Client : ID - " + clientID + " : Address - "
+ clientSocket.getInetAddress().getHostName()+"\n");
try {
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
PrintWriter out = new PrintWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
ObjectOutputStream objectOutput = new ObjectOutputStream(clientSocket.getOutputStream());
while (running) {
out.flush();
in.mark(0);
in.reset();
clientCommand = in.readLine();
try{
if(clientCommand == null){
} else {
clientCommand = clientCommand.replace("\"", "");
tokens = clientCommand.split(" ", 2);
commandName = tokens[0];
restofString = tokens[1];
}
} catch(ArrayIndexOutOfBoundsException e) {
//Handle ArrayIndexOutOfBoundsException
}
if (commandName.equalsIgnoreCase("LOGO")) {
System.out.print("Stopping client thread for client : " + clientID);
StacServ.chatText.append("Stopping client thread for client : " + clientID+"\n");
out.println("LOGO" + " logged out."+"\n");
out.flush();
running = false;
}
else if (commandName.equalsIgnoreCase("REGU")){
System.out.println("Client Says :" + clientCommand);
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
String[] keys = restofString.split("\"?( |$)(?=(([^\"]*\"){2})*[^\"]*$)\"?");
String uName = keys[0];
String uPass = keys[1];
String fName = keys[2];
String lName = keys[3];
StacServ.chatText.append("Attemplting to add client: " + fName + " " + lName);
dbconnection.createUser(uName, uPass, fName, lName);
out.println("REGR S");
out.flush();
}
else if (commandName.equalsIgnoreCase("CRCR")){
System.out.println("Client Says :" + clientCommand);
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
String[] keys = restofString.split("\"?( |$)(?=(([^\"]*\"){2})*[^\"]*$)\"?");
String className = keys[0];
String institution = keys[1];
String startDate = keys[2];
String endDate = keys[3];
String ipAddress = keys[4];
String meetDOW = keys[5];
StacServ.chatText.append("Attemplting to add class: " + className);
dbconnection.createClass(className, institution, startDate, endDate, ipAddress, meetDOW);
out.println("CRER S" + className);
out.flush();
}
else if (commandName.equalsIgnoreCase("CSRC")){
System.out.println("Client Says :" + clientCommand);
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
String[] keys = restofString.split("\"?( |$)(?=(([^\"]*\"){2})*[^\"]*$)\"?");
String className = keys[0];
String institution = keys[1];
if(institution == " "){
institution = "%";
}
StacServ.chatText.append("Attemplting to find class: " + className +" " + "\n");
ResultSet rs = dbconnection.searchClasses(className, institution);
//ResultSet rs = dbconnection.searchClasses(className, institution);
while(rs.next()){
queryResult.add(new ClassData(rs.getString("classID"), rs.getString("className"), rs.getString("adminID"), rs.getString("institution"), rs.getString("startDate"), rs.getString("endDate"), rs.getString("PublicIPAddress")));
String ctClassID = rs.getString("classID");
String ctClassName = rs.getString("className");
String ctAdminID = rs.getString("adminID");
String ctinstitution = rs.getString("institution");
String ctstartDate = rs.getString("startDate");
String ctendDate = rs.getString("startDate");
String ctipAddress = rs.getString("endDate");
out.println("CDTR S" + ctClassID + ctClassName + ctAdminID + ctinstitution + ctstartDate + ctendDate + ctipAddress);
StacServ.chatText.append("CDTR S" + " " + ctClassID + " " + ctClassName + " " + ctAdminID + " " + ctinstitution + " " + ctstartDate + " " + ctendDate + " " + ctipAddress + "\n");
}
}
else if (commandName.equalsIgnoreCase("CTDL")){
String[] keys = restofString.split("\"?( |$)(?=(([^\"]*\"){2})*[^\"]*$)\"?");
String classID = keys[0];
int classId = Integer.parseInt(classID);
System.out.println("Client Says :" + clientCommand);
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
StacServ.chatText.append("Attemplting to find class with ID: " + classId + "\n");
ResultSet rs = dbconnection.searchClasses(classId);
while(rs.next()){
queryResult.add(new ClassData(rs.getString("classID"), rs.getString("className"), rs.getString("adminID"), rs.getString("institution"), rs.getString("startDate"), rs.getString("endDate"), rs.getString("PublicIPAddress")));
String ctClassID = rs.getString("classID");
String ctClassName = rs.getString("className");
String ctAdminID = rs.getString("adminID");
String ctinstitution = rs.getString("institution");
String ctstartDate = rs.getString("startDate");
String ctendDate = rs.getString("startDate");
String ctipAddress = rs.getString("endDate");
out.println("CDTR S" + ctClassID + ctClassName + ctAdminID + ctinstitution + ctstartDate + ctendDate + ctipAddress);
StacServ.chatText.append("CDTR " + "S" + ctClassID + ctClassName + ctAdminID + ctinstitution + ctstartDate + ctendDate + ctipAddress + "\n");
}
}
else if (commandName.equalsIgnoreCase("ELST")){
StacServ.chatText.append("ELST TEST " + userName +"\n");
System.out.println("Client Says :" + clientCommand + "\n");
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
int userID = dbconnection.getUserID(userName);
ResultSet userClasses = dbconnection.getStudentsClasses(userID);
String dummy = Integer.toString(userID);
StacServ.chatText.append("userID is: " +dummy +"\n");
StacServ.chatText.append("Attemplting to find classes for user: " + userName + "\n");
sb = new StringBuilder("");
while(userClasses.next()){
String ctClassID = userClasses.getString("classID");
sb.append(ctClassID);
sb.append(" ");
}
out.println("ELSR S" + sb.toString() + "\n");
StacServ.chatText.append("ELSR S" + sb.toString() + "\n");
}
else if (commandName.equalsIgnoreCase("CLST")){
userName = "ejohn";
StacServ.chatText.append("ELST TEST " + userName +"\n");
System.out.println("Client Says :" + clientCommand + "\n");
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
int userID = dbconnection.getAdminsID(userName);
ResultSet userClasses = dbconnection.getAdminClasses(userID);
String dummy = Integer.toString(userID);
StacServ.chatText.append("userID is: " +dummy +"\n");
StacServ.chatText.append("Attemplting to find classes for user: " + userName + "\n");
userName = "CCDawg";
sb = new StringBuilder("");
while(userClasses.next()){
String ctClassID = userClasses.getString("classID");
sb.append(ctClassID);
sb.append(" ");
}
out.println("ELSR S" + sb.toString() + "\n");
StacServ.chatText.append("ELSR " + "S " + sb.toString() + "\n");
}
else if(commandName.equalsIgnoreCase("ENRL")){
System.out.println("Client Says :" + clientCommand);
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
userName = "CCDawg";
String flag = "0";
String[] keys = restofString.split("\"?( |$)(?=(([^\"]*\"){2})*[^\"]*$)\"?");
String classID = keys[0];
String deviceID = keys[1];
int classIDs = Integer.parseInt(classID);
dbconnection.addDevice(userName, classIDs, deviceID, flag);
}
else if(commandName.equalsIgnoreCase("CDRP")){
userName = "PillCosby";
String[] keys = restofString.split("\"?( |$)(?=(([^\"]*\"){2})*[^\"]*$)\"?");
String classID = keys[0];
int classIDs = Integer.parseInt(classID);
dbconnection.unenrollStudent(classIDs, userName);
}
else if (commandName.equalsIgnoreCase("REGA")){
System.out.println("Client Says :" + clientCommand);
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
String[] keys = restofString.split("\"?( |$)(?=(([^\"]*\"){2})*[^\"]*$)\"?");
String uName = keys[0];
String uPass = keys[1];
String fName = keys[2];
String lName = keys[3];
StacServ.chatText.append("Attempting to add Admin: " + fName + " " + lName);
dbconnection.createAdmin(uName, uPass, fName, lName);
out.println("REGA " + "S"+"\n");
out.flush();
}
else if (commandName.equalsIgnoreCase("LOGA")){
ResultSet rs = null;
System.out.println("Client Says :" + clientCommand+"\n");
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
String[] keys = restofString.split("\"?( |$)(?=(([^\"]*\"){2})*[^\"]*$)\"?");
String uName = keys[0];
String uPass = keys[1];
StacServ.chatText.append("Attempting to Login Admin: " + uName+"\n");
rs = dbconnection.checkAdmin(uName);
if(rs != null){
while(rs.next()){
String check = rs.getString(1);
if(uName.equals(check)){
check = rs.getString(2);
if(uPass.equals(check)){
StacServ.chatText.append("Admin: " + uName + " logged in."+"\n");
out.flush();
out.println("LOGR S");
userName = uName;
out.flush();
}
else{
StacServ.chatText.append("Admin: " + uName + "Incorrect username or password"+"\n");
out.flush();
out.println("LOGR " + "F"+"\n");
out.flush();
}
}
}
}
else{
StacServ.chatText.append("Admin: " + uName + "is not registered in the system");
out.println("LOGA " + "F"+"\n");
out.flush();
}
}
else if (commandName.equalsIgnoreCase("LOGU")){
ResultSet rs = null;
System.out.println("Client Says :" + clientCommand);
StacServ.chatText.append("Client Says :" + clientCommand+"\n");
StacServ.chatText.append(restofString +"\n");
//restofString = restofString.replaceAll("[\u0000-\u001f]", "");
String[] keys = restofString.split("\"?( |$)(?=(([^\"]*\"){2})*[^\"]*$)\"?");
String uName = keys[0];
String uPass = keys[1];
uName = uName.replace("\"", "");
uPass = uPass.replace("\"", "");
StacServ.chatText.append("Attempting to log in: " + uName+"\n");
rs = dbconnection.checkUser(uName);
if(rs != null){
while(rs.next()){
String check = rs.getString(1);
if(uName.equals(check)){
check = rs.getString(2);
if(uPass.equals(check)){
StacServ.chatText.append("User: " + uName + " logged in."+"\n");
out.println("LOGR S");
userName = uName;
out.flush();
}
else{
StacServ.chatText.append("User: " + uName + "\n" + "Incorrect password" +"\n");
out.println("LOGR F" + "\n");
out.flush();
}
}
}
}
else{
StacServ.chatText.append("Admin: " + uName + "is not registered in the system");
out.println("LOGR F");
out.flush();
}
}
else {
//out.println(clientCommand);
out.flush();
}
}
} catch (Exception e) {
//e.printStackTrace();
}
}
}最佳答案
您确定要使用ObjectOutputStream吗？
它将向底层的OutputStream输出一个序列化 header 。如果您想避免这种情况，但仍然有原始数据输出的方法(如果您有面向行的协议(protocol)，则可能不需要)，那么 DataOutputStream 提供相同的方法，但不带序列化 header 。
对于基于行的协议(protocol)，StreamWriter 是更好的选择。
关于Java 服务器程序在启动时吐出两个 U+FFFD 字符。需要帮助弄清楚它在哪里执行此操作以及为什么执行此操作？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40855330/