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)
Related
I'm creating a simple app which uses JDBC to get data from MySQL. I use a dao to get data from the database. All but one are working fine (code is the same for all DAOs). Also I'm committing INSERT and UPDATE methods manually.
Workbench returns valid result even if I set isolation level read committed manually.
JDBCSessionDao create method:
public void create(Session session) throws SQLException{
try(PreparedStatement ps = conn.prepareStatement(INSERT_SESSION)){
conn.setAutoCommit(false);
LocalTime start = session.getStartTime();
LocalTime end = session.getEndTime();
System.out.println(start + ", " + end);
System.out.println(Time.valueOf(start) + ", " + Time.valueOf(end));
ps.setTime(1, Time.valueOf(start));
ps.setTime(2, Time.valueOf(end));
ps.setDate(3, Date.valueOf(session.getDate()));
ps.setLong(4, session.getMovieId());
ps.executeUpdate();
conn.commit();
conn.setAutoCommit(true);
}
catch (SQLException e){
logger.error(e.getMessage());
conn.rollback();
}
}
JDBCSessionDao findByDate method
public List<Session> findByDate(LocalDate date) {
List<Session> sessions = new ArrayList<>();
SessionMapper mapper = new SessionMapper();
try(PreparedStatement ps = conn.prepareStatement(SELECT_BY_DATE_ORDER_BY_TIME_ASC)){
ps.setDate(1, Date.valueOf(date));
ResultSet rs = ps.executeQuery();
System.out.println(rs.getFetchSize());
while(rs.next()){
Session s = mapper.extractFromResultSet(rs);
sessions.add(s);
}
}
catch (SQLException e){
logger.error(e.getMessage());
}
return sessions;
}
Query:
String SELECT_BY_DATE_ORDER_BY_TIME_ASC = "SELECT * FROM sessions WHERE session_date=? ORDER by start_time ASC";
JDBCDaoFactory getConnection() method:
private Connection getConnection(){
String url = "jdbc:mysql://localhost:3306/cinemajee?useLegacyDatetimeCode=false&serverTimezone=Europe/Kiev";
String user = "root";
String password = "root";
try{
Class.forName("com.mysql.cj.jdbc.Driver");
return DriverManager.getConnection(url, user, password);
}
catch (SQLException | ClassNotFoundException e){
e.printStackTrace();
throw new RuntimeException();
}
}
Query result in workbench:
query result
Try modifying the query in your code. Perhaps the session_date parameter isn't working. So change from this:
"SELECT * FROM sessions WHERE session_date=? ORDER by start_time ASC"'
to this:
"SELECT * FROM sessions ORDER by start_time ASC LIMIT 5"'
I've forgot to change column names in SessionMapper, they were written in camel case (e.g. sessionId) but my db columns is in snake case (e.g. session_id).
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;
}
}
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.
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.
I have a problem trying to execute more than one query into my Java Application code.
I have a procedure that is called in main and is in the class "Fant":
public void XXX(){
Connectivity con=new Connectivity(); // this class set up the data for the connection to db; if ( !con.connect() ) {
System.out.println("Error during connection.");
System.out.println( con.getError() );
System.exit(0);
}
ArrayList<User> blabla=new ArrayList<User>();
blabla=this.getAllUsers(con);
for (User u:blabla)
{
try {
Connectivity coni=new Connectivity();//start a new connection each time that i perform a query
Statement t;
t = coni.getDb().createStatement();
String query = "Select count(*) as rowcount from berebe.baraba";
ResultSet rs = t.executeQuery(query);
int numPrenotazioni=rs.getInt("rowcount");
rs.close(); //close resultset
t.close(); //close statement
coni.getDb().close(); //close connection
}
}
catch (SQLException e)
{
System.err.println("SQLState: " +
((SQLException)e).getSQLState());
System.err.println("Error Code: " +
((SQLException)e).getErrorCode());
}
}
}
The called function is defined as:
ArrayList<User> getAllUsers(Connectivity con) {
try{
ArrayList<User> userArrayList=new ArrayList<User>();
String query = "Select idUser,bubu,lala,sisi,gogo,gg from berebe.sasasa";
Statement t;
t = con.getDb().createStatement();
ResultSet rs = t.executeQuery(query);
while (rs.next())
{
User utente=new User(....); //user fields got from query
userArrayList.add(utente);
}
rs.close();
t.close();
con.disconnect(); //disconnect the connection
return userArrayList;
} catch (SQLException e) {
}
return null;
}
The main is:
public static void main(String[] argv) {
ArrayList<User> users=new ArrayList<User>();
System.out.println("-------- MySQL JDBC Connection Testing ------------");
Fant style = new Fant();
style.XXX();
}
The query performed into "getAllusers" is executed and into the arraylist "blabla" there are several users; the problem is that the second query that needs the count is never executed.
The MYSQlState given when running is= "S1000" and the SQLERROR is "0".
Probably i'm mistaking on connections issues but i'm not familiar with statements,connections,resultsets.
Thank you.
You might forget to call rs.next() before getting the result form it in XXX()methods as shown below:
ResultSet rs = t.executeQuery(query);
// call rs.next() first here
int numPrenotazioni=rs.getInt("rowcount");