JSP case analysis (I)-Online Voting System-4-code analysis

The original source code does not have a myeclipse project, the database uses sqlserver2000, and the server uses tomcat.

I put all the code in myeclipse10, deployed to Apache-Tomcat-6.0.35, the database uses sqlserver2008, found that the original driver can also be used, you can also use (http://blog.csdn.net/flyuniverse_shell/article/details/7351016).

Source code successfully deployed on my local machine:

 

 

Key source code:

(Db. Java)

Package com. yxq. toolbean;

Import java. SQL. connection;
Import java. SQL. drivermanager;
Import java. SQL. statement;
Import java. SQL. resultset;
Import java. util. arraylist;
Import java. util. List;

Import com. yxq. valuebean. tempsingle;
Import com. yxq. valuebean. votesingle;

Public class dB {
Private string classname;

Private string URL;

Private string username;

Private string password;

Private connection con;

Private statement STM;

Private resultset RS;

Public dB (){
Classname = "com. Microsoft. JDBC. sqlserver. sqlserverdriver ";
Url = "JDBC: Microsoft: sqlserver: // localhost: 1433; databasename = db_vote ";
Username = "sa ";
Password = "xiexie ";
}

/**
* @ Function load database driver
*/
Public void loaddrive (){
Try {
Class. forname (classname );
} Catch (classnotfoundexception e ){
System. Out. println ("failed to load the database driver! ");
E. printstacktrace ();
}
}
 
/**
* @ Function get database connection
*/
Public void getcon (){
Loaddrive ();
Try {
Con = drivermanager. getconnection (URL, username, password );
} Catch (exception e ){
System. Out. println ("failed to connect to the database! ");
E. printstacktrace ();
}
}
 
/**
* @ Function get statement object
*/
Public void getstm (){
Getcon ();
Try {
STM = con. createstatement ();
} Catch (exception e ){
System. Out. println ("An error occurred while obtaining the statement object! ");
E. printstacktrace ();
}
}

/**
* @ Function: query a data table and obtain the result set.
*/
Public void getrs (string SQL ){
Getstm ();
Try {
Rs = cmd.exe cutequery (SQL );
} Catch (exception e ){
System. Out. println ("An error occurred while querying the database! ");
E. printstacktrace ();
}
}
 
/**
* @ Function query data tables and obtain voting options
*/
Public list selectvote (string SQL ){
List votelist = NULL;
If (SQL! = NULL &&! SQL. Equals ("")){
Getrs (SQL );
If (RS! = NULL ){
Votelist = new arraylist ();
Try {
While (Rs. Next ()){
Votesingle = new votesingle ();
Votesingle. setid (mytools. inttostr (Rs. getint (1 )));
Votesingle. settitle (Rs. getstring (2 ));
Votesingle. setnum (mytools. inttostr (Rs. getint (3 )));
Votesingle. setorder (mytools. inttostr (Rs. getint (4 )));
Votelist. Add (votesingle );
}
} Catch (exception e ){
System. Out. println ("An error occurred while encapsulating data in the tb_vote table! ");
E. printstacktrace ();
} Finally {
Closed ();
}
}
}
Return votelist;
}

/**
* @ Function query the data table to obtain the last voting record of the specified IP Address
*/
Public tempsingle selecttemp (string SQL ){
Tempsingle = NULL;
If (SQL! = NULL &&! SQL. Equals ("")){
Getrs (SQL );
If (RS! = NULL ){
Try {
While (Rs. Next ()){
Tempsingle = new tempsingle ();
Tempsingle. setid (mytools. inttostr (Rs. getint (1 )));
Tempsingle. setvoteip (Rs. getstring (2 ));
Tempsingle. setvotemsel (Rs. getlong (3 ));
Tempsingle. setvotetime (Rs. getstring (4 ));
}
} Catch (exception e ){
System. Out. println ("An error occurred while encapsulating data in the tb_temp table! ");
E. printstacktrace ();
} Finally {
Closed ();
}
}
}
Return tempsingle;
}
 
/**
* @ Function update data table
*/
Public int Update (string SQL ){
Int I =-1;
If (SQL! = NULL &&! SQL. Equals ("")){
Getstm ();
Try {
I = cmd.exe cuteupdate (SQL );
} Catch (exception e ){
System. Out. println ("failed to update database! ");
E. printstacktrace ();
} Finally {
Closed ();
}
}
Return I;
}
/**
* @ Function close database connection
*/
Public void closed (){
Try {
If (RS! = NULL)
Rs. Close ();
If (STM! = NULL)
STM. Close ();
If (con! = NULL)
Con. Close ();
} Catch (exception e ){
System. Out. println ("failed to close the database! ");
E. printstacktrace ();
}
}
}

 

Voting algorithm source code:

(Dovote. jsp)

<% @ Page contenttype = "text/html; charset = UTF-8" %>
<% @ Page import = "com. yxq. valuebean. tempsingle" %>
<% @ Page import = "com. yxq. toolbean. mytools" %>
<% @ Page import = "Java. util. Date" %>

<JSP: usebean id = "mydb" class = "com. yxq. toolbean. DB"/>
<%
String mess = "";
String selectid = request. getparameter ("Ilike"); // get the user selected
If (selectid = NULL | selectid. Equals ("") {// no selection
Mess = "select vote! ";
}
Else {// selected
Boolean mark = false; // indicates whether to allow voting.
Long today = (new date ()). gettime (); // new date () to obtain the current time. Call the gettime () method of the date class to obtain the number of milliseconds from 00:00:00, January 1, January 1, 1970 to the current time.
Long last = 0; // time of the last vote (displayed in milliseconds)
String IP = request. getremoteaddr (); // obtain the user IP Address
String SQL = "select * From tb_temp where votemsel = (select max (votemsel) from tb_temp where voteip = '" + IP + "')"; // SQL statement, function: obtain the record of the current user's last vote from the data table
Tempsingle single = mydb. selecttemp (SQL );
If (single = NULL) // The current IP address does not exist in the tb_temp table.
Mark = true; // allow voting
Else {// if the current IP address exists, it determines whether the specified time has exceeded from the last vote to the present. The system specifies 60 minutes.
Last = single. getvotemsel (); // obtain the last voting time from the JavaBean (displayed in milliseconds)
String result = mytools. comparetime (today, last); // compare the current time with the time of the last vote
If (result. Equals ("yes") // returns "yes", indicating that the time difference has exceeded 60 minutes and voting is allowed.
Mark = true;
Else // otherwise, voting is not allowed
Mark = false;
}

String strtime = mytools. formatdate (today); // convert the current voting time (displayed in milliseconds) to the "Year-month-day hour: minute: Second" Format
If (Mark) {// allow voting
/** [1] record the user IP address and voting time **/
SQL = "insert into tb_temp values ('" + IP + "', '" + today + "', '" + strtime + "')";
Int I = mydb. Update (SQL );

/** [2] determine whether the user's IP address is successfully recorded **/
If (I <= 0) // ip record failed
Mess = "An error occurred while recording your IP address! ";
Else {// ip address recorded successfully
/** Number of updated votes **/
SQL = "Update tb_vote set vote_num = vote_num + 1 where id =" + selectid;
I = mydb. Update (SQL); // update successful
If (I> 0)
Mess = "voting takes effect! ";
Else // update failed
Mess = "failed to vote! ";
}
}
Else {// voting not allowed
Mess = "Sorry, by judging your IP address, you have already voted! <Br> last voting time: "+ single. getvotetime () +" <br> no more voting is allowed within 60 minutes! ";
}
}

Session. setattribute ("mess", Mess); // Save the prompt information to the session range.
Response. sendredirect ("messages. jsp"); // redirect the request to the messages. jsp page to prompt
%>