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PostgreSQL: How to insert data into database table with loop?

Hello fellow Stackoverflowers!
I am trying to INSERT INTO a database table 'dotcom' 4 columns of 5000 rows of data from a text file in the form [x, w, x, y, z] e.g.
1 google com null null
2 google co uk null
...
and the rows returned remains '1' instead of '5000' for some reason.
The problem is that the rows are not inserted into the database table even though the BufferedReader reads it. How may I solve this problem? E.g. inserting the data into the table with a loop?
Any help would be greatly appreciated!
import java.sql.*;
import java.util.Scanner;
import java.io.*;
public class Database {
public static Connection connectToDatabase(String user, String port,
String database) {
System.out.println("-------- PostgreSQL JDBC Connection Testing ------------");
try {
Class.forName("org.postgresql.Driver");
} catch (ClassNotFoundException e) {
System.out.println("Where is your PostgreSQL JDBC Driver? " + "Include in your library path!");
e.printStackTrace();
}
System.out.println("PostgreSQL JDBC Driver Registered!");
Connection connection = null;
try {
connection = DriverManager.getConnection("jdbc:postgresql://localhost:" + port + "/" + database, user, "doesn't matter!");
} catch (SQLException e) {
System.out.println("Connection Failed! Check output console");
e.printStackTrace();
}
return connection;
}
public static ResultSet executeSelect(Connection connection, String query) {
Statement st = null;
try {
st = connection.createStatement();
} catch (SQLException e) {
e.printStackTrace();
return null;
}
ResultSet rs = null;
try {
rs = st.executeQuery(query);
//st.close();
} catch (SQLException e) {
e.printStackTrace();
return null;
}
return rs;
}
public static void dropTable(Connection connection, String table) {
Statement st = null;
try {
st = connection.createStatement();
st.execute("DROP TABLE " + table);
st.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void createTable(Connection connection,
String tableDescription) {
Statement st = null;
try {
st = connection.createStatement();
st.execute("CREATE TABLE " + tableDescription);
st.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static int insertIntoTableFromFile(Connection connection,
String table, String file) {
BufferedReader br = null;
int numRows = 0;
try {
Statement st = connection.createStatement();
String sCurrentLine, brokenLine[], composedLine = "";
br = new BufferedReader(new FileReader("src/TopURLs"));
while ((sCurrentLine = br.readLine()) != null) {
// Insert each line to the DB
brokenLine = sCurrentLine.split("\t");
composedLine = "INSERT INTO dotcom VALUES (";
int i;
for (i = 0; i < brokenLine.length - 1; i++) {
composedLine += "'" + brokenLine[i] + "',";
}
composedLine += "'" + brokenLine[i] + "')";
numRows = st.executeUpdate(composedLine);
//System.out.println(composedLine);
}
} catch (IOException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (br != null)
br.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
return numRows;
}
public static void main(String[] argv) throws SQLException {
/*
Scanner input = new Scanner(System.in);
System.out.println("Please enter your Username:");
String user = input.next();
System.out.println("Please enter your Port ID:");
String port = input.next();
*/
String user = "zbva777";
String port = "28046";
String database = "test";
Connection connection = connectToDatabase(user, port, database);
if (connection != null) {
System.out.println("You made it, take control your database now!");
} else {
System.out.println("Failed to make connection!");
return;
}
// Now we're ready to work on the DB
String query = "SELECT * FROM dotcom";
ResultSet rs = executeSelect(connection, query);
try {
while (rs.next()) {
System.out.print("Column 1 returned ");
System.out.println(rs.getString(1));
}
} catch (SQLException e) {
e.printStackTrace();
}
rs.close();
dropTable(connection, "dotcom");
createTable(connection, "dotcom (rank int primary key, name varchar(5000), type varchar(5000), subtype varchar(5000), subsubtype varchar(5000));");
int rows = insertIntoTableFromFile(connection, "dotcom", "src/TopURLs");
System.out.println(rows + " rows inserted.");
}
}

In each iteration of the loop you override numRows instead of incrementing it with the newly added row. Just replace the = with += and you should be OK:
numRows += st.executeUpdate(composedLine);
// Here ^
That being said, you should really look into PreparedStatements and executing batches.

PostgreSQL: How to print out ResultSet?

Hello fellow Stackoverflowers!
How do you print out a ResultSet's column e.g. 'name' (in order of number rank)?
I am stuck at the bottom of the main method # //Print data from result set
Thank you for your help!
import java.sql.*;
import java.util.Scanner;
import java.io.*;
public class Database {
public static Connection connectToDatabase(String user, String port,
String database) {
System.out.println("-------- PostgreSQL JDBC Connection Testing ------------");
try {
Class.forName("org.postgresql.Driver");
} catch (ClassNotFoundException e) {
System.out.println("Where is your PostgreSQL JDBC Driver? " + "Include in your library path!");
e.printStackTrace();
}
System.out.println("PostgreSQL JDBC Driver Registered!");
Connection connection = null;
try {
connection = DriverManager.getConnection("jdbc:postgresql://localhost:" + port + "/" + database, user, "doesn't matter!");
} catch (SQLException e) {
System.out.println("Connection Failed! Check output console");
e.printStackTrace();
}
return connection;
}
public static ResultSet executeSelect(Connection connection, String query) {
Statement st = null;
try {
st = connection.createStatement();
} catch (SQLException e) {
e.printStackTrace();
return null;
}
ResultSet rs = null;
try {
rs = st.executeQuery(query);
//st.close();
} catch (SQLException e) {
e.printStackTrace();
return null;
}
return rs;
}
public static void dropTable(Connection connection, String table) {
Statement st = null;
try {
st = connection.createStatement();
st.execute("DROP TABLE " + table);
st.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void createTable(Connection connection,
String tableDescription) {
Statement st = null;
try {
st = connection.createStatement();
st.execute("CREATE TABLE " + tableDescription);
st.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static int insertIntoTableFromFile(Connection connection,
String table, String file) {
BufferedReader br = null;
int numRows = 0;
try {
Statement st = connection.createStatement();
String sCurrentLine, brokenLine[], composedLine = "";
br = new BufferedReader(new FileReader("src/TopURLs"));
while ((sCurrentLine = br.readLine()) != null) {
// Insert each line to the DB
brokenLine = sCurrentLine.split("\t");
composedLine = "INSERT INTO dotcom VALUES (";
int i;
for (i = 0; i < brokenLine.length - 1; i++) {
composedLine += "'" + brokenLine[i] + "',";
}
composedLine += "'" + brokenLine[i] + "')";
numRows += st.executeUpdate(composedLine);
//System.out.println(composedLine);
}
} catch (IOException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (br != null)
br.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
return numRows;
}
public static void print() {
System.out.println("########## 1st Query ##########");
}
public static void main(String[] argv) throws SQLException {
/*
Scanner input = new Scanner(System.in);
System.out.println("Please enter your Username:");
String user = input.next();
System.out.println("Please enter your Port ID:");
String port = input.next();
*/
String user = "zbva777";
String port = "28046";
String database = "test";
Connection connection = connectToDatabase(user, port, database);
if (connection != null) {
System.out.println("You made it, take control your database now!");
} else {
System.out.println("Failed to make connection!");
return;
}
// Now we're ready to work on the DB
// connection is of type Connection (in JDBC)
DatabaseMetaData dbm = connection.getMetaData();
// check if table is there
ResultSet tables = dbm.getTables(null, null, "dotcom", null);
if (tables.next()) {
System.out.println("Table exists");
} else {
System.out.println("Table does not exist");
}
// check if view is there?
//"create view foo as select * from table;"
//"select * from foo;"
ResultSet views = dbm.getTables("catalog name", null, null, null);
if (views.next()) {
System.out.println("View exists");
} else {
System.out.println("View does not exist");
}
String query = "SELECT * FROM dotcom";
String view = "CREATE VIEW view as SELECT FROM dotcom";
ResultSet rs = executeSelect(connection, query);
try {
while (rs.next()) {
//System.out.print("Column 1 returned ");
//System.out.println(rs.getString(1));
}
} catch (SQLException e) {
e.printStackTrace();
}
dropTable(connection, "dotcom");
createTable(connection, "dotcom (rank int primary key, name varchar(128), type varchar(128), subtype varchar(128), subsubtype varchar(128));");
int rows = insertIntoTableFromFile(connection, "dotcom", "src/TopURLs");
System.out.println(rows + " rows inserted.");
//Print data from result set
print();
while(rs.next()) {
rs.getInt("rank");
String name = rs.getString("name");
System.out.println(name);
}
rs.close();
}
}

PostgreSQL: How do you insert rows of data with a loop into a database table?

How can you read & insert rows from a text file containing data in [x, y, z] form for example:
1 google com (separated by tabs)
into a database table (without having to insert every single line manually)?
I'm new at programming!
Thank you for your time and help kind sirs and madams!
import java.sql.*;
import java.util.Scanner;
import java.io.*;
public class Database {
public static Connection connectToDatabase(String user, String port, String database) {
System.out.println("-------- PostgreSQL " + "JDBC Connection Testing ------------");
try {
Class.forName("org.postgresql.Driver");
} catch (ClassNotFoundException e) {
System.out.println("Where is your PostgreSQL JDBC Driver? " + "Include in your library path!");
e.printStackTrace();
}
System.out.println("PostgreSQL JDBC Driver Registered!");
Connection connection = null;
try {
connection = DriverManager.getConnection("jdbc:postgresql://localhost:" + port + "/" + database, user,
"doesn't matter!");
} catch (SQLException e) {
System.out.println("Connection Failed! Check output console");
e.printStackTrace();
}
return connection;
}
public static ResultSet executeSelect(Connection connection, String query) {
Statement st = null;
try {
st = connection.createStatement();
} catch (SQLException e) {
e.printStackTrace();
return null;
}
ResultSet rs = null;
try {
rs = st.executeQuery(query);
st.close();
} catch (SQLException e) {
e.printStackTrace();
return null;
}
return rs;
}
public static void dropTable(Connection connection, String table) {
Statement st = null;
try {
st = connection.createStatement();
st.execute("DROP TABLE " + table);
st.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void createTable(Connection connection, String tableDescription) {
Statement st = null;
try {
st = connection.createStatement();
st.execute("CREATE TABLE " + tableDescription);
st.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static int insertIntoTableFromFile(Connection connection, String table, String file) {
BufferedReader br = null;
int numRows = 0;
try {
Statement st = connection.createStatement();
String sCurrentLine, brokenLine[], composedLine = "";
br = new BufferedReader(new FileReader(file));
while ((sCurrentLine = br.readLine()) != null) {
// Insert each line to the DB
brokenLine = sCurrentLine.split("\t");
composedLine = "INSERT INTO dotcom VALUES (";
int i;
for (i = 0; i < brokenLine.length - 1; i++) {
composedLine += "'" + brokenLine[i] + "',";
}
composedLine += "'" + brokenLine[i] + "')";
numRows = st.executeUpdate(composedLine);
}
} catch (IOException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (br != null)
br.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
return numRows;
}
public static void main(String[] argv) throws SQLException, FileNotFoundException {
#SuppressWarnings("resource")
Scanner input = new Scanner(System.in);
System.out.println("Please enter your Username:");
String user = input.next();
System.out.println("Please enter your Port ID:");
String port = input.next();
String database = "test";
Connection connection = connectToDatabase(user, port, database);
Statement st = connection.createStatement();
if (connection != null) {
System.out.println("You made it, take control your database now!");
} else {
System.out.println("Failed to make connection!");
return;
}
// Now we're ready to work on the DB
// read TopURLs file
try {
BufferedReader fileReader = new BufferedReader(new FileReader("TopURLs"));
while (fileReader.readLine() != null) {
st.execute("DROP TABLE IF EXISTS dotcom;");
st.execute("CREATE TABLE dotcom (rank integer PRIMARY KEY, domainName varchar(128), domainType varchar(128));");
st.execute("INSERT INTO dotcom VALUES(1, 'google', 'com');");
//st.execute("INSERT INTO dotcom VALUES(2, 'facebook', 'com');");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
}
/*
try {
BufferedReader fileReader = new BufferedReader(new FileReader("TopURLs"));
while (fileReader.readLine() != null) {
st.execute("DROP TABLE IF EXISTS dotcom;");
st.execute("CREATE TABLE dotcom (rank integer PRIMARY KEY, domainName varchar(128), domainType varchar(128));");
st.execute("INSERT INTO dotcom SELECT com, domainType FROM dotcom WHERE domainType = 'com'");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
}
*/
/*
Statement createStatement = null;
PreparedStatement insertStatement = null;
try {
BufferedReader fileReader = new BufferedReader(new FileReader("TopURLs"));
String line = null;
createStatement = connection.createStatement();
createStatement.executeUpdate("DROP TABLE IF EXISTS dotcom");
createStatement.executeUpdate("CREATE TABLE dotcom (rank integer PRIMARY KEY, domainName varchar(128), domainType varchar(128))");
connection.setAutoCommit(false);//commit whole batch at the end
insertStatement = connection.prepareStatement("INSERT INTO dotcom VALUES (?, ?, ?)");
while ( (line = fileReader.readLine()) != null) {
line = fileReader.readLine();
String[] urls = line.split("\t");//space or any other delimiter that you're using
insertStatement.setInt(1, Integer.parseInt(urls[0]));
insertStatement.setString(2, urls[1]);
insertStatement.setString(3, urls[2]);
//insertStatement.setString(4, urls[3]);
insertStatement.addBatch();
}
insertStatement.executeBatch();
connection.commit();
} catch (IOException e) {
e.printStackTrace();
} finally {
if(connection != null) {
connection.setAutoCommit(true);
}
if(createStatement != null) {
createStatement.close();
}
if(insertStatement != null) {
insertStatement.close();
}
}
*/
// connection is of type Connection (in JDBC)
DatabaseMetaData dbm = connection.getMetaData();
// check if table is there
ResultSet tables = dbm.getTables(null, null, "table name", null);
if (tables.next()) {
System.out.println("Table exists");
} else {
System.out.println("Table does not exist");
}
// check if view is there?
//"create view foo as select * from table;"
//"select * from foo;"
ResultSet views = dbm.getTables("catalog name", null, null, null);
if (views.next()) {
System.out.println("View exists");
} else {
System.out.println("View does not exist");
}
String query = "SELECT * FROM internet";
ResultSet rs = executeSelect(connection, query);
try {
while (rs.next()) {
System.out.print("Column 1 returned ");
System.out.println(rs.getString(1));
}
} catch (SQLException e) {
e.printStackTrace();
}
rs.close();
dropTable(connection, "dotcom");
createTable(connection,
"dotcom (id int primary key, name varchar(15), type varchar(15));");
int rows = insertIntoTableFromFile(connection, "dotcom", "TopURLs");
System.out.println(rows + " rows inserted.");
}
}

This is too long for a comment.
When loading data from a text file, I generally load into a staging table that consists of character column. Then, I can do validate the data, convert to the appropriate data types, and even reparse some columns, if necessary.
Admittedly, the Postgres COPY command often works quite well just reading in the data.
You would seem to have two options:
Load the data into a staging table and do the data cleansing there.
Read the data line-by-line in java and do the data cleansing there.
Because my SQL skills >> my java skills, it is a no-brainer which I would choose (SQL). But these would seem to be your most reasonable options.

Java - SQLITE_BUSY; database file is locked

My application reads a html table and then a script (TableToCSV) converts it into a .csv format. After that I convert that .csv into a sqlite database. After that I run queries on the database. Problem is that upon executing, it shows that SQLITE_BUSY; database file is locked.
Whats the reason of this and how can I fix this?
Here is my code -
final JFileChooser fileDialog = new JFileChooser();
JButton btnInputFile = new JButton("Input File");
btnInputFile.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
int returnVal = fileDialog.showOpenDialog(rootPane);
if (returnVal == JFileChooser.APPROVE_OPTION) {
java.io.File file = fileDialog.getSelectedFile();
String name = file.getName();
name = name.substring(0, name.lastIndexOf("."));
name += ".html";
File newFile = new File(file.getParentFile(), name);
if (file.renameTo(newFile)) {
try {
TableToCSV tableToCSV = new TableToCSV(newFile, ',', '\"', '#', CSV.UTF8Charset );
System.out.println("action");
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try
{
BufferedReader br=new BufferedReader(new FileReader("v.csv"));
String line;
while((line=br.readLine())!=null)
{
System.out.println(line);
String[]value = line.split(",");
System.out.println(value.length);
String sql = "INSERT into main ([Ticket #], Status, Priority, Department, [Account Name]) "
+ "values ('"+value[0]+"','"+value[1]+"','"+value[2]+"','"+value[3]+"','"+value[4]+"')";
PreparedStatement pst = DatabaseConnection.ConnectDB().prepareStatement(sql);
pst.executeUpdate();
}
br.close();
}
catch(Exception e)
{
JOptionPane.showMessageDialog(null, e);
}
}
}
});
UPDATE - DatabaseConnection.java
public class DatabaseConnection {
Connection conn = null;
Statement stmt = null;
public static Connection ConnectDB() {
try {
Class.forName("org.sqlite.JDBC");
Connection conn = DriverManager.getConnection("jdbc:sqlite:database.db");
conn.setAutoCommit(true);
return conn;
} catch (Exception e) {
JOptionPane.showMessageDialog(null, e);
return null;
}
}
}

It's probably due to you having multiple open references to the sqlite database.
I'd start by closing your PreparedStatement in a finally block inside your while loop.
PreparedStatement pst = null;
try{
pst = DatabaseConnection.ConnectDB().prepareStatement(sql);
pst.executeUpdate();
}finally{
if(pst != null) {
pst.close();
}
}
You should also close the database connection at the end of everything.
If that doesn't fix it, then please explain more about how you "convert that .csv into a sqlite database"

using combobox selectedItem on a function

i have an function connexion to a database
and i have a code that i have a select and display elements in a combobox
so i want pass on class connexion.java the combobox selectedItem becaue it contains the all of databases that i have
so i want tha classe connexion be dynamic so pass the element selected on this class
i don"t know how can i do that please help me
public class Connexion {
private static Connection conn;
{
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException ex) {
Logger.getLogger(Connexion.class.getName()).log(Level.SEVERE, null, ex);}
try {
conn = DriverManager.getConnection("jdbc:mysql://localhost/mohammedia", "root", "123456");
} catch (SQLException ex) {
Logger.getLogger(Connexion.class.getName()).log(Level.SEVERE, null, ex); }
}
public static Connection getconx()
{
return conn;
}
}

Use this class
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.naming.NamingException;
import org.apache.commons.dbcp.BasicDataSource;
import sun.jdbc.rowset.CachedRowSet;
public class SQLConnection {
private static Connection con = null;
private static BasicDataSource dataSource;
//we can enable and disable connection pool here
//true means connection pool enabled,false means disabled
private static boolean useConnectionPool = true;
private static int count=0;
private SQLConnection() {
/*
Properties properties = new Properties();
properties.load(new FileInputStream(""));
maxActive = properties.get("maxActive");
*/
}
public static String url = "jdbc:mysql://localhost:3306/schemaname";
public static String password = "moibesoft";
public static String userName = "root";
public static String driverClass = "com.mysql.jdbc.Driver";
public static int maxActive = 20;
public static int maxIdle = 10;
private static final String DB_URL = "driver.classs.name";
private static final String DB_USERNAME = "database.username";
static {
/*Properties properties = new Properties();
try {
properties.load(new FileInputStream("D:\\CollegeBell\\properties\\DatabaseConnection.properties"));
//properties.load(new FileInputStream("E:\\vali\\CollegeBell\\WebContent\\WEB-INF"));
//properties.load(new FileInputStream("D:\\DatabaseConnection.properties"));
url = properties.getProperty(DB_URL);
System.out.println(url);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}*/
dataSource = new BasicDataSource();
dataSource.setDriverClassName(driverClass);
dataSource.setUsername(userName);
dataSource.setPassword(password);
dataSource.setUrl(url);
dataSource.setMaxActive(maxActive);
dataSource.setMinIdle(maxIdle);
dataSource.setMaxIdle(maxIdle);
}
//public static Connection getConnection(String opendFrom) throws SQLException,
public static Connection getConnection(String openedFrom) {
count++;
System.out.println("nos of connection opened till now="+count);
System.out.println("Connection opended from "+openedFrom);
// System.out.println("Connection Opended ");
try {
if (useConnectionPool) {
con = dataSource.getConnection();
System.out.println(dataSource.getMinEvictableIdleTimeMillis());
//dataSource.setMaxWait(15000);
System.out.println(dataSource.getMaxWait());
System.out.println(count );
} else {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection(url, userName, password);
}
}
//System.out.println("Connection : " + con.toString());
catch (SQLException e) {
e.printStackTrace();
}
catch (Exception e) {
e.printStackTrace();
}
return con;
}
public static void closeConnection(Connection con, String closedFrom)
{
//System.out.println("Connection closed from: " + con.toString());
// System.out.println("Connection closed from: " + closedFrom);
//log.info("Connection closed from: " + closedFrom);
if(con != null){
count--;
System.out.println("Connection count value after closing="+count);
System.out.println("Connection closed from: " + closedFrom);
try {
con.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
//added by nehal
public static void closeStatement(Statement ps, String closedFrom)
{
if(ps != null){
System.out.println("Statement closed from: " + closedFrom);
try {
ps.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public static void closePreparedStatement(PreparedStatement ps, String closedFrom)
{
if(ps != null){
System.out.println("Statement closed from: " + closedFrom);
try {
ps.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public static void closeResultSet(ResultSet rs, String closedFrom)
{
if(rs != null){
System.out.println("ResultSet closed from: " + closedFrom);
try {
rs.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
//added by nehal
/*public static ResultSet executeQuery(String query) throws Exception {
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
CachedRowSet crset = null;
try {
con = getConnection();
stmt = con.createStatement();
rs = stmt.executeQuery(query);
crset = new CachedRowSet();
crset.populate(rs);
} catch (Exception e) {
throw e;
} finally {
if (rs != null) {
rs.close();
}
if (stmt != null) {
stmt.close();
}
if (con != null && !con.isClosed()) {
con.close();
}
}
return crset;
}
public static int executeUpdate(String query) throws Exception {
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
int rows = -1;
try {
con = getConnection();
stmt = con.createStatement();
rows = stmt.executeUpdate(query);
} catch (Exception e) {
throw e;
} finally {
if (rs != null) {
rs.close();
}
if (stmt != null) {
stmt.close();
}
if (con != null && !con.isClosed()) {
con.close();
}
}
return rows;
}
public static boolean execute(String query) throws Exception {
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
boolean rowsreturned = false;
try {
con = getConnection();
stmt = con.createStatement();
rowsreturned = stmt.execute(query);
} catch (Exception e) {
throw e;
} finally {
if (rs != null) {
rs.close();
}
if (stmt != null) {
stmt.close();
}
if (con != null && !con.isClosed()) {
con.close();
}
}
return rowsreturned;
}*/
/*
* public static void closeConnection(Connection con) { try { con.close();
* con=null; } catch (SQLException e) { // TODO Auto-generated catch block
* e.printStackTrace(); } }
*/
}

A JComboBox accepts any kind of object, so you can simply do something like this.
Connection con = new Connection();
JComboBox box = getBox();
box.addItem(con);
And to retreive the value:
JComboBox box = getBox();
Connection con = (Connection)box.getSelectedItem();
However in your Connection class you must override the toString() function, because this is used to display the box.
class Connection
{
public String toString()
{
return "BoxItemDisplayvalue"; <--- here you must put something meaningfull which is displayed in the box.
}
}
So you can instantiate a connection representing the connection that you want, and when the user selects an item from the combobox, you will have the connection it represents.

For what i understand, you have 2 classes..
One the gui where you have a comboBox with the schema name where u want to get connected.
So you have to have a EventListener to "listen" when the submit button is pressed.
For example:
Connection con = null;
JButton submitButton = new JButton("Confirm db");
submitButton.addActionListener(new MyConnectionListener());
..
//Could be inner class
class MyConnectionListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent evt){
if(cmb.getSelectedItem() != null){
con = Connection.getConx(cmb.getSelectedItem().toString());
}
}
}
And in your Connexion class
public class Connexion {
public static Connection getconx(String schema)
{
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException ex) {
Logger.getLogger(Connexion.class.getName()).log(Level.SEVERE, null, ex);}
try {
conn = DriverManager.getConnection("jdbc:mysql://localhost/"+schema, "root", "123456");
} catch (SQLException ex) {
Logger.getLogger(Connexion.class.getName()).log(Level.SEVERE, null, ex); }
}
return conn;
}
}