private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
Connection connection;
PreparedStatement ps;
try {
connection = DriverManager.getConnection("jdbc:mysql://localhost/testdb", "root", "pokemon12");
ps = connection.prepareStatement("SELECT * FROM users WHERE UserName = ? AND Password = ?");
ps.setString(1, jTextField1.getText());
ps.setString(2, String.valueOf(jPasswordField1.getPassword()));
ResultSet rs = ps.executeQuery();
if(rs.next()){
System.out.println(rs.getString(1));
System.out.println(rs.getString(2));
setVisible(false);
NewApplication1 mf = new NewApplication1(rs.getString(1),rs.getString(2));
mf.setVisible(true);
}else{
JOptionPane.showMessageDialog(this, "Username Or Password Are Invalid");
System.out.println(rs.getString(1));
System.out.println(rs.getString(2));
}
} catch (SQLException ex) {
Logger.getLogger(NewJFrame.class.getName()).log(Level.SEVERE, null, ex);
}
}
i dont know why i keep getting java.sql.SQLException: Illegal operation on empty result set even tho my sql table isnt empty and the row im trying to get also isnt empty, it happens when i try to select the last and second to last row in the table, excuse my lack of knowledge im very new to sql.
I am working on a program which will when finished allow the end user to keep track of there sound packs in a database through SQLite. The newest problem I am running into is that I can not get the Select statement to take a JTextField input. The reason that I want to do this is that I already have the text fields linked through the insert method. I have tried switching the variable types in the readAllData method and I am not entirely sure what other way to fix it.
The fields are as follows
PackId
PackName
VendorName
PackValue
what I want to happen is when I hit the Update button I want the data in the database to print out to the console (for now) and I am also going to be adding a select specified records method as well.
Here is the code I do apologize in advance this is a very long project:
public void readAllData() throws SQLException {
Connection conn = DriverManager.getConnection("jdbc:sqlite:packsver3.db");
PreparedStatement ps = null;
ResultSet rs = null;
try {
String sql = "SELECT * FROM packs";
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
while(rs.next()) {
String PackId = PackId.getText();
String PackName = PackName.getText();
String VendorName = VendorName.getTextField();
String PackValue = rs.getTextField;
System.out.println("All Packs\n");
System.out.println("PackId: " +PackId);
System.out.println("PackName: " +PackName);
System.out.println("VendorName: " +VendorName);
System.out.println("PackValue: " +PackValue+"\n\n");
}
} catch (SQLException e) {
System.out.println(e.toString());
}finally {
try {
assert rs != null;
rs.close();
ps.close();
conn.close();
} catch (SQLException e) {
System.out.println(e.toString());
}
Console Output
I'm trying to read string values from my database to insert them in an arraylist of strings. However, my loop stops after completing only one row.
That's my code,
public void initialize(URL arg0, ResourceBundle arg1) {
Statement stmt = null;
String query = "SELECT CustomerName FROM CUSTOMER WHERE CustomerName IS NOT NULL";
try {
Connection conn1 = DBConnection.getConnection();
stmt = conn1.createStatement();
ResultSet rs = stmt.executeQuery(query);
// iterate through the java resultset
while (rs.next()) {
System.out.println(rs.getString("CustomerName"));
customersnames.add(rs.getString("CustomerName"));
}
stmt.close();
} catch (Exception e) {
System.out.println("Exception at initialize ");
System.err.println(e.getMessage());
}
try {
TextFields.bindAutoCompletion(customer, customersnames);
} catch (NullPointerException E) {
}
}
and that's what I'm getting
null (that's in red)
heee
Exception at initialize
"heee" is the first row of my database, but I have many more, that's what it's reading only and it's throwing an exception.
Apparently, you get a NullPointerException after having printed the result of the first row.
Did you initialize your object customersnames?
In order to be sure, change System.err.println(e.getMessage()); into e.printStackTrace()
I've connected to a MySQL database, which contains four fields (the first of which being an ID, the latter ones each containing varchar strings).
I am trying to get the last row of the database and retrieve the contents of the fields so that I can set them to variables (an int and three strings) and use them later.
So far, I have the bare minimum to make the connection, where do I go from here? As you can see I have tried to write a SQL statement to get the last row but it's all gone wrong from there and I don't know how to split it into the separate fields.
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost/t", "", "");
Statement st = con.createStatement();
String sql = ("SELECT * FROM posts ORDER BY id DESC LIMIT 1;");
st.getResultSet().getRow();
con.close();
Here you go :
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost/t", "", "");
Statement st = con.createStatement();
String sql = ("SELECT * FROM posts ORDER BY id DESC LIMIT 1;");
ResultSet rs = st.executeQuery(sql);
if(rs.next()) {
int id = rs.getInt("first_column_name");
String str1 = rs.getString("second_column_name");
}
con.close();
In rs.getInt or rs.getString you can pass column_id starting from 1, but i prefer to pass column_name as its more informative as you don't have to look at database table for which index is what column.
UPDATE : rs.next
boolean next()
throws SQLException
Moves the cursor froward one row from its current position. A
ResultSet cursor is initially positioned before the first row; the
first call to the method next makes the first row the current row; the
second call makes the second row the current row, and so on.
When a call to the next method returns false, the cursor is positioned
after the last row. Any invocation of a ResultSet method which
requires a current row will result in a SQLException being thrown. If
the result set type is TYPE_FORWARD_ONLY, it is vendor specified
whether their JDBC driver implementation will return false or throw an
SQLException on a subsequent call to next.
If an input stream is open for the current row, a call to the method
next will implicitly close it. A ResultSet object's warning chain is
cleared when a new row is read.
Returns:
true if the new current row is valid; false if there are no more rows Throws:
SQLException - if a database access error occurs or this method is called on a closed result set
reference
Something like this would do:
public static void main(String[] args) {
Connection con = null;
Statement st = null;
ResultSet rs = null;
String url = "jdbc:mysql://localhost/t";
String user = "";
String password = "";
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection(url, user, password);
st = con.createStatement();
rs = st.executeQuery("SELECT * FROM posts ORDER BY id DESC LIMIT 1;");
if (rs.next()) {//get first result
System.out.println(rs.getString(1));//coloumn 1
}
} catch (SQLException ex) {
Logger lgr = Logger.getLogger(Version.class.getName());
lgr.log(Level.SEVERE, ex.getMessage(), ex);
} finally {
try {
if (rs != null) {
rs.close();
}
if (st != null) {
st.close();
}
if (con != null) {
con.close();
}
} catch (SQLException ex) {
Logger lgr = Logger.getLogger(Version.class.getName());
lgr.log(Level.WARNING, ex.getMessage(), ex);
}
}
}
you can iterate over the results with a while like this:
while(rs.next())
{
System.out.println(rs.getString("Colomn_Name"));//or getString(1) for coloumn 1 etc
}
There are many other great tutorial out there like these to list a few:
http://www.vogella.com/articles/MySQLJava/article.html
http://www.java-samples.com/showtutorial.php?tutorialid=9
As for your use of Class.forName("com.mysql.jdbc.Driver").newInstance(); see JDBC connection- Class.forName vs Class.forName().newInstance? which shows how you can just use Class.forName("com.mysql.jdbc.Driver") as its not necessary to initiate it yourself
References:
http://zetcode.com/databases/mysqljavatutorial/
This should work, I think...
ResultSet results = st.executeQuery(sql);
if(results.next()) { //there is a row
int id = results.getInt(1); //ID if its 1st column
String str1 = results.getString(2);
...
}
Easy Java method to get data from MySQL table:
/*
* CREDIT : WWW.CODENIRVANA.IN
*/
String Data(String query){
String get=null;
try{
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = (Connection)DriverManager.getConnection
("jdbc:mysql://localhost:3306/mysql","root","password");
Statement stmt = (Statement) con.createStatement();
ResultSet rs=stmt.executeQuery(query);
if (rs.next())
{
get = rs.getString("");
}
}
catch(Exception e){
JOptionPane.showMessageDialog (this, e.getMessage());
}
return get;
}
Here is what I just did right now:
import java.sql.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import com.sun.javafx.runtime.VersionInfo;
public class ConnectToMySql {
public static ConnectBean dataBean = new ConnectBean();
public static void main(String args[]) {
getData();
}
public static void getData () {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/mynewpage",
"root", "root");
// here mynewpage is database name, root is username and password
Statement stmt = con.createStatement();
System.out.println("stmt " + stmt);
ResultSet rs = stmt.executeQuery("select * from carsData");
System.out.println("rs " + rs);
int count = 1;
while (rs.next()) {
String vehicleType = rs.getString("VHCL_TYPE");
System.out.println(count +": " + vehicleType);
count++;
}
con.close();
} catch (Exception e) {
Logger lgr = Logger.getLogger(VersionInfo.class.getName());
lgr.log(Level.SEVERE, e.getMessage(), e);
System.out.println(e.getMessage());
}
}
}
The Above code will get you the first column of the table you have.
This is the table which you might need to create in your MySQL database
CREATE TABLE
carsData
(
VHCL_TYPE CHARACTER(10) NOT NULL,
);
First, Download MySQL connector jar file, This is the latest jar file as of today [mysql-connector-java-8.0.21].
Add the Jar file to your workspace [build path].
Then Create a new Connection object from the DriverManager class, so you could use this Connection object to execute queries.
Define the database name, userName, and Password for your connection.
Use the resultSet to get the data based one the column name from your database table.
Sample code is here:
public class JdbcMySQLExample{
public static void main(String[] args) {
String url = "jdbc:mysql://localhost:3306/YOUR_DB_NAME?useSSL=false";
String user = "root";
String password = "root";
String query = "SELECT * from YOUR_TABLE_NAME";
try (Connection con = DriverManager.getConnection(url, user, password);
Statement st = con.createStatement();
ResultSet rs = st.executeQuery(query)) {
if (rs.next()) {
System.out.println(rs.getString(1));
}
} catch (SQLException ex) {
System.out.println(ex);
}
}
I successfully can delete an integer but when I tried to make it a STRING it says
"unknown column itemtodelete in where clause but my ITEMTODELETE is a STRING declared in the database not an integer how much It doesn't delete a STRING?
below is my code:
private void DeleteButtonActionPerformed(java.awt.event.ActionEvent evt) {
int del = (prompt):
if (del == JOptionPane.YES_OPTION){
DelCurRec();
}
}
public void DelCurRec() {
String id = field.getText();
String SQL = "DELETE FROM inventory WHERE ItemCode = "+id+" ";
try {
Class.forName(connectio);
} catch (Exception e) {
JOptionPane.showMessageDialog(null,""+e.getMessage(),"JDBC Driver Error",JOptionPane.WARNING_MESSAGE);
}
Statement stmt = null;
Connection con = null;
//Creates connection to database
try {
con = DriverManager.getConnection("Connection");
stmt = con.createStatement();
} catch (Exception e) {
JOptionPane.showMessageDialog(null,""+e.getMessage(),"Connection Error",JOptionPane.WARNING_MESSAGE);
}
//Execute the SQL statment for deleting records
try {
stmt.executeUpdate(SQL);
//This closes the connection to the database
con.close();
//This closes the dialog
JOptionPane.showMessageDialog(null,"Deleted Succesfully","Delete Successful",JOptionPane.WARNING_MESSAGE);
} catch (Exception e) {
JOptionPane.showMessageDialog(null,""+e.getMessage(),"Communication Error",JOptionPane.WARNING_MESSAGE);
}
}
Do NOT use a Statement use a PreparedStatement instead, otherwise your application will be vulnerable to SQL injections. E.g. someone enters a string like: "'; drop table inventory; --"
The corresponding prepared statment would look something like:
String SQL = "DELETE FROM inventory WHERE ItemCode = ? ";
PreparedStatement pstmt = null;
// get a connection and then in your try catch for executing your delete...
pstmt = con.prepareStatement(SQL);
pstmt.setString(1, id);
pstmt.executeUpdate();
try changing the line:
String SQL = "DELETE FROM inventory WHERE ItemCode = "+id+" ";
to
String SQL = "DELETE FROM inventory WHERE ItemCode = '"+id+"' ";
I think you need to pass Integer.parseInt(id) and not id...assuming your id is int
This worked for me:
Statement stmt=con.createStatement();
stmt.executeUpdate("DELETE FROM student WHERE reg_number='R18854';");