Re: Java / JSP / MySQL

"ck" <>
17 Jan 2007 09:54:03 -0800
On Jan 17, 3:37 pm, wrote:

I got it partly to work using this great tutorial, but I'm not able to
do insert querys yet, select and update querys are working fine but
with insert querys I get an exception:

org.apache.jasper.JasperException: Exception in JSP: /index.jsp:21

18: db.connect();
20: try {
21: i = db.insert("INSERT INTO `sessions` (`ip`) VALUES
22: out.println(i);
23: }

Java Class:

        public int insert(String sql) throws SQLException {
                Statement s = con.createStatement();
                int res = s.executeUpdate(sql);
                return (res == 0) ? null : res;

        public int update(String sql) throws SQLException {
                Statement s = con.createStatement();
                int res = s.executeUpdate(sql);
                return (res == 0) ? null : res;

Again, the update query works but the insert is not working :s

Why don't you write a plain Java class that handles all the database
interaction? Call the relevant method when required in the JSP(Though
IMO thats a bad design, better way would be to use Servlets to handle
such actions). Something like this

// import relevant classes

public class DatabaseManager {
  private Resultset rs = null;

  public DatabaseManager(){ connect(); //establish connection when
creating object }

  public void connect(){ // implementation for database connection }

  public void insert(){ // implementation for insert in to table }

  public void otherMethods(){ // provide other methods which involve
database interaction }

  public String [] myTableList(){ // provide implementation for
populating items from mytable
  ArrayList list = new ArrayList();
  while (

Your original JSP code would be reduced to

<%@ page import="DatabaseManager" %>
// Perform all the operations needed using DatabaseManager class
DatabaseManager dm = new DatabaseManager();
//Iterate over dm.myTableList()

I have not written the implementation as you already know how to
connect to database and what query to be executed.
Note that this approach is a bad way of solving big application. BTW I
did not quite understand what you mean by

the next stap for me was finding a logical way of
creating a database connection for a Wizard Application

Can you explain that a bit more?


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