Tip:通过socket访问数据库,分 Clinet, Display,sqlServer三个类

Client.java

import java.awt.*;
import java.io.*;
import java.net.*;
import java.applet.*;

public class Client extends Applet
{
public TextArea chat_txt;
private TextField sql_txt;
private Button connect,execute;
private Socket soc= null;
private PrintStream ps= null;
Listen listen;

public void init()
{
chat_txt= new TextArea();
sql_txt= new TextField(20);
connect= new Button("Connect");
execute= new Button("Execute");
execute.disable();

Panel pp= new Panel();
pp.setLayout(new FlowLayout());
pp.add(sql_txt);
pp.add(connect);
pp.add(execute);

add("North",pp);
add("Center",chat_txt);
}

public boolean action(Event evt,Object obj)
{
if(evt.target instanceof Button)
{
String label= (String)obj;
if(label.equals("Connect"))
{

try{
soc= new Socket(InetAddress.getLocalHost(),4700);
ps= new PrintStream(soc.getOutputStream());
ps.println("HELLO");
ps.flush();
listen= new Listen(this,soc);
listen.start();
}catch(Exception e)
{
chat_txt.setText(e.toString());
disconnect();
}
connect.setLabel("Disconnect");
execute.enable();
}else if(label.equals("Disconnect"))
disconnect();
else if(label.equals("Execute"))
{
if(sql_txt.getText()!= null)
{
ps.println("FIND");
ps.flush();
ps.println(sql_txt.getText());
ps.flush();
}
}
}
return false;
}

public void disconnect()
{
if(soc!= null)
{
try{
listen.stop();
ps.println("QUIT");
ps.flush();
soc.close();
}catch(Exception e){}
finally{
listen.stop();
listen= null;
soc= null;
}
execute.disable();
connect.setLabel("Disconnect");
}
}
}

class Listen extends Thread
{
Socket socket= null;
DataInputStream dis= null;
Client parent= null;

public Listen(Client p,Socket s)
{
parent= p;
socket= s;
try{
dis= new DataInputStream(socket.getInputStream());
}catch(Exception e){}
}

public void run()
{
String line= null;

while(true)
{
try{
line= dis.readLine();
}catch(Exception e){}
if(line!= null)
parent.chat_txt.appendText(line);
}
}
}


Display.java

/********************************************
格式化输出数据库记录,出自<<使用java进行SQL数据库程序设计>>
返回值为格式化的字符串
********************************************/
import java.sql.*;

class Display extends Object
{
ResultSet theResultSet;
String theResult;

public void display()
{}

public void setResult(ResultSet result)
{
theResultSet= result;
}

public String getString()
throws SQLException,NoClassDefFoundError
{
theResult= "";
ResultSetMetaData metaData= theResultSet.getMetaData();
int colcount = metaData.getColumnCount();
int colSize[]= new int[colcount];
String colLabel[]= new String[colcount];
int colType[]= new int[colcount];
String colTName[]= new String[colcount];
int colPrec[]= new int[colcount];
int colScale[]= new int[colcount];

theResult +=" ";
for(int i= 1;i<= colcount;i++)
{
colSize[i-1] = metaData.getColumnDisplaySize(i);
colLabel[i-1]= metaData.getColumnLabel(i);
colType[i-1] = metaData.getColumnType(i);
colTName[i-1]= metaData.getColumnTypeName(i);
colPrec[i-1] = metaData.getPrecision(i);
colScale[i-1]= metaData.getScale(i);

if(colSize[i-1]<1+ colLabel[i-1].length())
colSize[i-1]= 1+colLabel[i-1].length();
theResult+= rightPad(colLabel[i-1],colSize[i-1]);
}

theResult +=" ";
int row= 0;

while(theResultSet.next())
{
row++;
for(int i=1;i<= colcount;i++)
{
String colvalue= theResultSet.getString(i);
if(colvalue== null)
colvalue="";
theResult+= rightPad(colvalue,colSize[i-1]);
}
theResult+=" ";
}
theResult+=" (" +row+ "rows included) ";
return theResult;
}

private String rightPad(String s,int len)
{
int curlen= s.length();
if(curlen>len)
return repString("*",len);
return (s+repString(" ",(len-curlen)));
}

private String repString(String s,int times)
{
String result="";
for(int i=0;i<times;i++)
result+= s;
return result;
}
}


sqlServer.java

import java.awt.*;
import java.sql.*;
import java.io.*;
import java.net.*;
import Display;

public class sqlServer
{
public static void main(String[] args)
{
System.out.println("Waiting for connection");

try{
ServerSocket session= new ServerSocket(4700);
handleRequests handler= null;
System.out.println("Waiting for connection");
while(true)
{
Socket socket= null;
socket= session.accept();
if(socket== null)
continue;
System.out.println("Connection made");
handler= new handleRequests(socket);
handler.start();
}
}catch(Exception e)
{
System.out.println("客户连接失败"+e);
}
}
}

class handleRequests extends Thread
{
private DataInputStream in= null;
private PrintStream out= null;
private Socket socket= null;

Connection theConnection= null;
Statement theStatement= null;
ResultSet theResultSet= null;
Display display= null;

public handleRequests(Socket s)
throws IOException
{
socket= s;
in= new DataInputStream(socket.getInputStream());
out= new PrintStream(socket.getOutputStream());
}

public void openConnection()
{
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
if(theConnection!= null)
theConnection.close();
theConnection= DriverManager.getConnection("jdbc:odbc:test","admin","1234");
theStatement= theConnection.createStatement();
display= new Display();
}catch(Exception e)
{
System.out.println(e);
}
}

public void run()
{
openConnection();
try{
String line= null;
while(true)
{
line = in.readLine();
if(line!= null)
line= line.trim();
if(line.equals("FIND"))
{
line = in.readLine();
line= line.trim();
theResultSet= theStatement.executeQuery(line);
display.setResult(theResultSet);
out.print(display.getString());
out.flush();
}
if(line.equals("QUIT"))
break;
if(line.equals("HELLO"))
{
out.println("Welcome to join us");
out.flush();
}
}
in.close();
out.close();
socket.close();
}catch(Exception e)
{
System.out.println(e);
}
}
}