Well, I'm trying to use SQLite in my Libgdx game, but don't know how.
public class Main {
public static void main(String[] args){
LwjglApplicationConfiguration config = new LwjglApplicationConfiguration();
config.title = Game.TITLE;
config.width = Game.V_WIDTH * Game.SCALE;
config.height = Game.V_HEIGHT * Game.SCALE;
new LwjglApplication(new Game(), config);
}}
What I need to do in my main? lol
I've been looking for this but, all I can find is related to Android application.
I already have the driver in my ref libraries, and connection class..
What I usually do when using a database with an application, is make a ConnectionFactory, that returns a new connection to the database.
public class ConnectionFactory {
public static Connection getConnection() {
Connection con = null;
Class.forName("org.sqlite.JDBC");
con = DriverManager.getConnection("jdbc:sqlite:test.db"); //change to whatever db you want
return con;
}
}
now we have a ConnectionFactory that can pump out connections to our database. Now when we want to interact with the database, you can get the connection appropriately. inside your main, it might look something like this:
public static void main(String[] args) {
Connection con = null;
String firstName = null, lastName = null;
try {
con = ConnectionFactory.getConnection();
PreparedStatement pstmt = con.prepareStatement("SELECT * FROM myTable where myId = ?");
pstmt.setInt(1, /*some id here, ill put this as example:*/ 1234567);
//execute the query and put into result set so we can get the values.
ResultSet rs = pstmt.executeQuery();
//the resultset iterates through rows, by calling next
if( rs.next() ) //could be while(rs.next()) if expecting multiple rows
{
firstName = rs.getString("firstName"); //column name you want to grab here
lastName = rs.getString("lastName");
}
} catch(SQLException sqle) {
sqle.printStackTrace();
}
finally {
try {
con.close(); //dont forget to close your connection to database!
} catch(SQLException sqle) {
sqle.printStackTrace();
}
}
}
You will need to create tables within the SQLite database and insert records before you can do any interactions though, so keep that in mind.
Related
So I'm currently working on a project that will be using a database but its my first time trying fiddling with it on java.
But I'm already seeing my first problem is how would i make one single file that handles connection while other files handles GET/ADD/UPDATE/DELETE (one for each table) what would properly be the best way on doing this ?
To not having to place connection values in each file and do the connection
I though about extending the connection class with the other classes but idk if its a great idea.
import java.sql.*;
public class DatabaseConnection {
public static void main(String[] args) {
final String url = "jdbc:postgresql://localhost:5432/Database";
final String user = "dbuser";
final String password = "dbpass";
try(Connection conn = DriverManager.getConnection(url, user, password)) {
System.out.println("Connection successful!");
} catch (SQLException e) {
System.out.println("Connection failure.");
e.printStackTrace();
}
}
}
What would be the best approach?
Maybe i'm wrong, but i think you need connection pool.
Try to find instruction here https://www.baeldung.com/java-connection-pooling
You could move the database connection related code to a utility class, and use the PreparedStatement class to precompile the SQL Query
public class doSomething {
Connection conn = null;
PreparedStatement pst = null;
public static void main(String [] args){
conn = DatabaseConnection.connect()
String qry = "Select * from table_name";
pst = (PreparedStatement) conn.prepareStatement(qry);
}
}
I'll try my best to make this as clear as possible since I'm new to Java. If there are parts which are unclear to you, please let me know. I apologize beforehand if the structure of my coding is messy.
I'm making a combobox event wherein if an item is selected (or changed), it will display items of that database and if the Update button is clicked, the program will connect to the database based on the item selected in the combobox.
The problem is that the variable cn after the if-else statement, has an error of "variable may have not been initialized".
Please note that I would like to focus on the condition since it is where I'm having difficulties and that the Update part is not a concern at this time.
private void btn_UpdateActionPerformed(java.awt.event.ActionEvent evt)
{
String value2 = (String) combobox_location.getSelectedItem();
String value4 = (String) combobox_category.getSelectedItem();
try
{
if(value2.equals(value4))
{
Connection cn = db.itemconnector.getConnection();
}
String sql = "UPDATE items set location = '"+value2+"' where id = '"+value4+"' " ; //Please ignore this line for the now
PreparedStatement ps1 = cn.prepareStatement(sql);
ps1.execute();
JOptionPane.showMessageDialog(null, "Update Successful");
PreparedStatement ps2 = cn.prepareStatement(ref);
ResultSet rs = ps2.executeQuery();
DefaultTableModel tm = (DefaultTableModel)itemTable.getModel();
tm.setRowCount(0);
while(rs.next())
{
Object o[] = {rs.getInt("id"), rs.getString("location"), rs.getString("product_name"),rs.getString("product_category"),rs.getString("product_description"),rs.getInt("product_stock"), rs.getFloat("product_price"), rs.getString("product_status")};
tm.addRow(o);
}
}
catch (Exception e)
{
System.out.println("Update Error!");
}
}
I have a package db that has itemconnector class for database connection and here is my code I've written in it. I hope I have provided all necessary details for your assistance. If you need more info, please let me know. Thank you.
package db;
import java.sql.*;
public class itemconnector {
/**
*
* #return
* #throws Exception
*/
public static Connection getConnection() throws Exception
{
Class.forName("com.mysql.jdbc.Driver");
Connection cn = (Connection)
DriverManager.getConnection("jdbc:mysql://192.168.1.50:3306/sales","root","");
return cn;
}
public static Connection getConnection1() throws Exception
{
Class.forName("com.mysql.jdbc.Driver");
Connection cn = (Connection)
DriverManager.getConnection("jdbc:mysql://192.168.1.50:3306/sales1","root","");
return cn;
}
public static Connection getConnection2() throws Exception
{
Class.forName("com.mysql.jdbc.Driver");
Connection cn = (Connection)
DriverManager.getConnection("jdbc:mysql://192.168.1.50:3306/sales2","root","");
return cn;
}
}
When Try to fetching Data in database result it come zero row but when try to copy and past query on mysql has return specific number of rows needed.
Connection to mysql server
private Connection connection() {
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/olesdb", "root", "");
} catch (Exception e) {
//System.out.println("Connection error");
}
return con;
}
**
My function for fetching data
**
public List<AcademicYearCourses> getStudentCourse(int studentID, int academicYear,int semester) throws SQLException{
List<AcademicYearCourses> list = new ArrayList<>();
PreparedStatement sta = connection().prepareStatement("SELECT courseCode,courseName FROM courses co,studentprograms stpro,academicyearcourse acco WHERE stpro.studentID=? AND acco.academicYearID=? AND acco.semesterID=? AND stpro.programID= acco.programID AND stpro.studyYear=acco.studyYear AND acco.courseID=co.courseID");
sta.setInt(1, studentID);
sta.setInt(2, academicYear);
sta.setInt(3, semester);
ResultSet res = sta.executeQuery();
while(res.next()){
AcademicYearCourses acco = new AcademicYearCourses();
acco.setAcdemicYearCourseID(rs.getInt("acdemicYearCourseID"));
acco.setCourseName(rs.getString("courseName"));
acco.setCourseCode(rs.getString("courseCode"));
list.add(acco);
}
return list;
}
So I need help to solve this issue it very important in my project and Cant continue without this data
Your are doing rs.getInt("acdemicYearCourseID") but column acdemicYearCourseID is not in your SELECT columns list.
Also try changing getInt("..."), getString("...") to getInt(1), getString(2)
i have been using this JDBC conection in all of my class that had to run query but i created a new class which i dont want the constructor with a parameter of the DConnection from JDBC Class(main Database Class).
but i keep on getting NullPointExceptions. Can anyway figur out what that problem may be.
Thanks.
public class UsersDao {
// associating the Database Connection objekt
private DConnector connector;
private final Connection myConn;
// Constructor
public UsersDao() throws CZeitExceptionHand,SQLException {
myConn = connector.getConnenction();
}
public boolean updateUsers(String mitarb, int mid) throws SQLException{
// PreparedStatement myStmt = null;
Statement stmt = myConn.createStatement();
try {
String myStmt = "SELECT Bly "
+ "" + mid + ";";
return stmt.execute(myStmt);
} finally {
close(stmt);
}
}
Example like this Method which is working but in different class
String[][] getAllTheWorkers(DConnector connector) throws CZeitExceptionHand {
try {
Connection connect = connector.getConnenction();
Statement stmt = connect.createStatement();
ResultSet result = stmt.executeQuery("SELECT ");
result.last();
int nt = result.getRow();
result.beforeFirst();
}
return results;
} catch (SQLException e) {
throw new CZeitExceptionHand("Error: " + e);
}
}
The object does not seem to be initialized.
Can you please post which method is not working and from where it is invoked ?
P.S : Unable to add a comment - that is why have answered !
What is the problem in this code? where it is update the all column values with the same last one .
public class dbconnection {
java.sql.Connection con;
java.sql.Statement st;
ResultSet rs;
public EncBean getConnection()throws SQLException{
EncBean encBean1 = new EncBean();
String v_url= "jdbc:oracle:thin:#192.168.2.138:1522:orcl2";
String v_username= "scott";
String v_password = "tiger";
try
{
DriverManager.registerDriver(new oracle.jdbc.OracleDriver());
con = DriverManager.getConnection(v_url,v_username,v_password);
System.out.println ("Connection to Oracle database was Established");
}
catch ( SQLException e)
{
e.printStackTrace();
}
return encBean1;
}
public EncBean selectRows()
{
EncBean encBean2 = new EncBean();
try
{
String SQLselect="select JOB_NAME from job";
st=con.createStatement();
rs=st.executeQuery(SQLselect);
while (rs.next()) {
encBean2.setName(rs.getString("JOB_NAME"));
}
}
catch ( Exception ex )
{
ex.printStackTrace();
}
return encBean2;
}
public void updateRows(String updatedname){
try
{
Statement stmt = con.createStatement(ResultSet.TYPE_FORWARD_ONLY,ResultSet.CONCUR_UPDATABLE);
ResultSet srs = stmt.executeQuery("select job_name from job " );
while (srs.next()) {
srs.updateString("job_name", updatedname);
srs.updateRow();
con.commit();}
System.out.println("An existing user was updated successfully!");}
catch(SQLException err){
System.out.println(err.getMessage());
}}}
This is the main
public class mainenc {
public static void main(String[] args) throws Exception{
dbconnection dbcon = new dbconnection();
EncBean encbeancon= dbcon.getConnection();
EncBean encBean5 = dbcon.selectRows();
enc concatinputs = new enc();
EncBean encBeanconcat = concatinputs.funconcat(encBean5.getName());
EncBean encBean4 = concatinputs.inputencryption(encBeanconcat.getConcatenatedData());
String vReserverbin= encBean4.getReversedBinary();
String ascistring= concatinputs.convertBinaryStringToString(vReserverbin);
dbcon.updateRows(ascistring);
}}
What is the problem in this code? where it is update the all column values with the same last one .
After updated method you should write list method again.
Try to take this example:
UPDATE tableB
SET tableB.value , tableA.value, tableB.value)
WHERE tableA.name = 'Joe'
It is kind of obvious: dbcon.updateRows(...) calls for the update method and that method does the job.
But as Erhan said, you don't get to see the result because you don't actually make use of updated records, e.g. show them etc. At least, you can check it out at the DB level if op is completed.
But I really disliked your comment:
plz can you do it for me?
You should do your own task and ask help when you need a hand. But never expect someone else to do your job mate.