【发布时间】：2019-02-11 16:22:21
【问题描述】：
我正在用 java 实现一个多线程的客户端-服务器应用程序。我想在这个程序中实现 JDBC 并且我希望我的服务器在启动时从数据库中检索数据。我会将这些数据存储在我的collection 实例中，对数据执行操作，当服务器完成执行时，我需要将数据存储回数据库。问题是服务器处于无限循环等待客户端，我无法弄清楚如何让服务器停止。
这是我的服务器程序：
import java.io.*;
import java.text.*;
import java.util.*;
import java.net.*;
public class Server
{
public static void main(String[] args) throws IOException
{
// server is listening on port 5056
ServerSocket ss = new ServerSocket(5056);
// running infinite loop for getting
// client request
while (true)
{
Socket s = null;
try {
// socket object to receive incoming client requests
s = ss.accept();
System.out.println("A new client is connected : " + s);
// obtaining input and out streams
DataInputStream dis = new DataInputStream(s.getInputStream());
DataOutputStream dos = new DataOutputStream(s.getOutputStream());
System.out.println("Assigning new thread for this client");
// create a new thread object
Thread t = new ClientHandler(s, dis, dos);
// Invoking the start() method
t.start();
}
catch (Exception e) {
s.close();
e.printStackTrace();
}
}
}
}
// ClientHandler class
class ClientHandler extends Thread
{
DateFormat fordate = new SimpleDateFormat("yyyy/MM/dd");
DateFormat fortime = new SimpleDateFormat("hh:mm:ss");
final DataInputStream dis;
final DataOutputStream dos;
final Socket s;
// Constructor
public ClientHandler(Socket s, DataInputStream dis, DataOutputStream dos)
{
this.s = s;
this.dis = dis;
this.dos = dos;
}
@Override
public void run()
{
String received;
String toreturn;
while (true) {
try {
// Ask user what he wants
dos.writeUTF("What do you want?[Date | Time]..\n"+
"Type Exit to terminate connection.");
// receive the answer from client
received = dis.readUTF();
if(received.equals("Exit"))
{
System.out.println("Client " + this.s + " sends exit...");
System.out.println("Closing this connection.");
this.s.close();
System.out.println("Connection closed");
break;
}
// creating Date object
Date date = new Date();
// write on output stream based on the
// answer from the client
switch (received) {
case "Date" :
toreturn = fordate.format(date);
dos.writeUTF(toreturn);
break;
case "Time" :
toreturn = fortime.format(date);
dos.writeUTF(toreturn);
break;
default:
dos.writeUTF("Invalid input");
break;
}
}
catch (IOException e) {
e.printStackTrace();
}
}
try
{
// closing resources
this.dis.close();
this.dos.close();
}
catch(IOException e){
e.printStackTrace();
}
}
}
这是我的客户程序：
import java.io.*;
import java.net.*;
import java.util.Scanner;
// Client class
public class Client
{
public static void main(String[] args) throws IOException
{
try
{
Scanner scn = new Scanner(System.in);
// getting localhost ip
InetAddress ip = InetAddress.getByName("localhost");
// establish the connection with server port 5056
Socket s = new Socket(ip, 5056);
// obtaining input and out streams
DataInputStream dis = new DataInputStream(s.getInputStream());
DataOutputStream dos = new DataOutputStream(s.getOutputStream());
// the following loop performs the exchange of
// information between client and client handler
while (true)
{
System.out.println(dis.readUTF());
String tosend = scn.nextLine();
dos.writeUTF(tosend);
// If client sends exit,close this connection
// and then break from the while loop
if(tosend.equals("Exit"))
{
System.out.println("Closing this connection : " + s);
s.close();
System.out.println("Connection closed");
break;
}
// printing date or time as requested by client
String received = dis.readUTF();
System.out.println(received);
}
// closing resources
scn.close();
dis.close();
dos.close();
}
catch(Exception e){
e.printStackTrace();
}
}
}
【问题讨论】：
-
谁有能力在您的设计中关闭服务器？是客户吗？它是一个特殊的客户端（即管理员客户端）吗？还是你在服务器端关闭？
-
@Impurity 它既不是客户也不是特殊客户。我在服务器端关闭了
-
为什么用 JDBC 来标记它？除了您提到想要使用 JDBC 之外，我在您的问题（也不是您的代码）中看不到为什么这实际上与您的问题相关。
-
@MarkRotteveel 它是由 Impurity 在编辑中添加的。我没有包括
-
@Impurity 你为什么这样做？除非有明确的原因，否则您不应更改问题的范围或标记，而这里没有。
标签： java multithreading server client