The database uses mysql. The database creation code is not provided. Please add it yourself. Add the user table to the database, with three rows of fields. This code can be used as a common paging component.
The first file PagedbClass. java
| The Code is as follows: |
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Package com. kanba. tools;
Import java. SQL .*;
Import com. kanba. connection. Conn;
Public class PagedbClass {
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
ResultSetMetaData resultsMeta = null;
Int rows = 0;
Public PagedbClass (){
Con = new Conn (). getConnection ();
}
Public ResultSet executeQuery (String SQL) throws SQLException {
ResultSet rs = null;
Try {
Stmt = con. createStatement ();
Rs = stmt.exe cuteQuery (SQL );
While (rs. next ())
This. rows ++;
Rs = stmt.exe cuteQuery (SQL );
}
Catch (SQLException e ){
System. out. print ("Query:" + e. getMessage ());
}
This. rs = rs;
Return rs;
}
Public boolean executeUpdate (String SQL ){
Try {
Stmt = con. createStatement ();
Stmt.exe cuteUpdate (SQL );
Return true;
}
Catch (SQLException e ){
System. out. print ("Update:" + e. getMessage ());
Return false;
}
}
Public int getColumns (){
Int columns = 0;
Try {
This. resultsMeta = this. rs. getMetaData ();
Columns = this. resultsMeta. getColumnCount ();
}
Catch (SQLException e ){}
Return columns;
}
Public int getRows (){
Return this. rows;
}
Public void closedb (){
Try {
Con. close ();
} Catch (SQLException e ){
E. printStackTrace ();
}
}
} |
The second file paging generic class PageQuery. java
| The Code is as follows: |
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Package com. kanba. tools;
Import java. SQL .*;
Import javax. servlet. http .*;
Public class PageQuery {
Int Offset; // record Offset
Int Total; // The Total number of records.
Int MaxLine; // number of records displayed per page
ResultSet rs; // read the result
Int TPages; // the total number of pages.
Int CPages; // current page number
String PageQuery; // display the parameters to be passed by PAGE
String Query; // query statement
String QueryPart; // query part after "FROM"
String FilePath;
PagedbClass db; // object of dbclass
// Constructer do nothing
Public PageQuery (){
// Ten lines are displayed on each page.
MaxLine = 30;
Db = new PagedbClass ();
}
***************
// Main working function, which reads the corresponding records from the table based on the given conditions
Public ResultSet myQuery (String query, HttpServletRequest req) throws SQLException {
String query_part, OS;
Int begin, offset;
// Intercept query statements after "FROM"
Begin = query. indexOf ("FROM ");
Query_part = query. substring (begin, query. length (). trim ();
// Calculate the offset
OS = req. getParameter ("offset ");
If (OS = null) Offset = 0;
Else Offset = Integer. parseInt (OS );
// Get the file name
FilePath = req. getRequestURI ();
Query = query;
QueryPart = query_part;
// Calculate the total number of records
String SQL = "SELECT Count (*) AS total" + this. QueryPart;
Rs = db.exe cuteQuery (SQL );
If (rs. next ())
Total = rs. getInt (1 );
// Set the current page number and total page number
TPages = (int) Math. ceil (double) this. Total/this. MaxLine );
CPages = (int) Math. floor (double) Offset/this. MaxLine + 1 );
// Retrieve the required records based on conditions
If (Total> 0 ){
SQL = Query + "LIMIT" + Offset + "," + MaxLine;
Rs = db.exe cuteQuery (SQL );
}
Return rs;
}
Public void close (){
Db. closedb ();
}
// Display the total number of pages
Public int getTotalPages (){
Return TPages;
}
// Display the current page number
Public int getCurrenPages (){
Return CPages;
}
// *********** Display the page turning prompt bar *************
// Display the home page, next page, last page, and last page
Public String PageLegend (){
String str = "";
Int first, next, prev, last;
First = 0;
Next = Offset + MaxLine;
Prev = Offset-MaxLine;
Last = (this. TPages-1) * MaxLine;
If (Offset> = MaxLine)
Str + = "<A href =" + FilePath + "? Offset = "+ first +"> homepage </A> ";
Else str + = "Homepage ";
If (prev> = 0)
Str + = "<A href =" + FilePath + "? Offset = "+ prev +"> previous page </A> ";
Else str + = "front page ";
If (next <Total)
Str + = "<A href =" + FilePath + "? Offset = "+ next +"> next page </A> ";
Else str + = "";
If (TPages! = 0 & CPages <TPages)
Str + = "<A href =" + FilePath + "? Offset = "+ last +"> last page </A> ";
Else str + = "last page ";
Str + = "Page:" + getCurrenPages () + "/" + getTotalPages () + "page ";
Str + = MaxLine + "entries/page" + "Total" + Total + "entries ";
String pageNum;
Return str;
}
}
|
Database connection file Conn. java
| The Code is as follows: |
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Package com. kanba. connection
Import java. SQL .*;
Public class Conn {
Public Conn (){}
// This is the code used to connect to the database. It can also be implemented through connection pools and other technologies.
String driverClass = "org. gjt. mm. mysql. Driver ";
String url = "jdbc: mysql: // localhost/test? User = root & password = 0 & useUnicode = true & characterEncoding = gb2312 ";
String username = "root ";
String password = "pwd ";
Connection conn = null; // Initialization
Public Connection getConnection ()
{
Try {
Class. forName (driverClass); // load the driver
// System. out. println ("jiazaichenggong ");
} Catch (ClassNotFoundException e ){
E. printStackTrace ();
}
Try {
Conn = DriverManager. getConnection (url); // create a connection conn
} Catch (SQLException e ){
E. printStackTrace ();
}
Return conn;
}
}
Paging test file page. jsp
<% @ Page language = "java" import = "java. SQL. *, com. kanba. tools. *" %>
<% @ Page contentType = "text/html; charset = gb2312" %>
<Jsp: useBean id = "pq" scope = "page" class = "com. kanba. tools. PageQuery"/>
<Html>
<Body bgcolor = "#8BA9C9">
<Table bgcolor = "# fecda9" cellspacing = 0>
<%
String query = "SELECT * FROM users"; // note that this "FROM" must be capitalized, and the total number of rows must be determined by the query statement after the FROM statement in the program.
ResultSet rs = pq. myQuery (query, request );
String bar = pq. PageLegend (); // read the paging prompt bar
Out. println ("<tr> <td colspan = 2>" + bar + "</td> </tr> ");
Out. println ("<tr> <td colspan = 2> While (rs. next ()){
// Description: rs. getString (2) is the position corresponding to the column name. Do not use rs. getString ("colmn_name ").
%>
<Tr> <td> <% = rs. getString (1) %> </td> <% = rs. getString (2) %> </td> </tr>
<%}
Rs. close; pq. close ();
%>
</Table>
</Body>
</Html> |
