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How to get the list of all database names from a Sybase DB Server in java

I want to get the list of all database names from a Sybase DB server. I can connect the Sybase db through Java, but don't know how to get the list of database names. I am using jconn4 jar file.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import com.sybase.jdbc4.jdbc.SybDriver;
public class ConnectToSybase {
public static Connection conn = null;
public static Statement stmt = null;
public static SybDriver sybDriver = null;
public static ResultSet rs = null;
public static String dbServerIP = "10.10.10.11";
public static String portNo = "5000";
public static String dbName = "NewDB";
public static void main(String[] args) {
try {
Class.forName("com.sybase.jdbc4.jdbc.SybDriver").newInstance();
System.out.println("Driver loaded");
conn = DriverManager.getConnection("jdbc:sybase:Tds:" + dbServerIP + ":" + portNo, "usrname", "password");
stmt = conn.createStatement();
} catch (Exception e) {
System.out.println("In exception");
e.printStackTrace();
} finally {
try {
rs.close();
stmt.close();
conn.close();
} catch (Exception e) {
}
}
}
}

I found myself a working code.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import com.sybase.jdbc4.jdbc.SybDriver;
public class ConnectToSybase {
public static Connection conn = null;
public static Statement stmt = null;
public static SybDriver sybDriver = null;
public static ResultSet rs = null;
public static String dbServerIP = "10.10.10.11";
public static String portNo = "5000";
public static String dbName = "NewDB";
public static void main(String[] args) {
try {
Class.forName("com.sybase.jdbc4.jdbc.SybDriver").newInstance();
System.out.println("Driver loaded");
conn = DriverManager.getConnection("jdbc:sybase:Tds:" + dbServerIP + ":" + portNo, "usrname", "password");
stmt = conn.createStatement();
List<String> dbList = new ArrayList<String>();
// getting list of DB names from the DB server
ResultSet rs = conn.getMetaData().getCatalogs();
while (rs.next()) {
dbList.add(rs.getString(1));
}
for (String list : dbList) {
System.out.println(list);
}
} catch (Exception e) {
System.out.println("In exception");
e.printStackTrace();
} finally {
try {
rs.close();
stmt.close();
conn.close();
} catch (Exception e) {
}
}
}
}

Data Access object method not working

I am a student learning JSP, and I seem to have this issue in executing a method via an object of a DAO class. When the database connectivity and SQL query is given on the servlet itself it, it will work. But when given in the DAO class and a object is used, it doesn't work. Please help.
import dataaccessobjects.cartDAO1;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class addtoCartServ extends HttpServlet {
#Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
cartDAO1 newcart = new cartDAO1();
PrintWriter out = response.getWriter();
if (request.getParameter("submit") != null){
//out.println("added to cart");
try {
//out.println("submit not null");
String Uname = (String) request.getSession().getAttribute("Welcome");
String ino = request.getParameter("ino");
String iqnty = request.getParameter("quantity");
String iname = request.getParameter("iname");
if(newcart.addToCart(iname,Uname,ino,iqnty)){
out.println("added to cart");
}
} catch (SQLException ex) {
Logger.getLogger(addtoCartServ.class.getName()).log(Level.SEVERE, null, ex);
} catch (ClassNotFoundException ex) {
Logger.getLogger(addtoCartServ.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
The DAO class
public cartDAO1(){
}
public boolean addToCart(String iname,String username, String ino,String iqnty) throws SQLException, ClassNotFoundException{
boolean flag = false;
Class.forName("org.apache.derby.jdbc.ClientDriver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/styleomega","root","");
PreparedStatement ps = conn.prepareStatement("INSERT INTO cart(iname,uname,ino,iqnty) VALUES (?,?,?,?)");
// set the values for parameters
ps.setString(1,iname);
ps.setString(2,username);
ps.setString(3,ino);
ps.setString(4,iqnty);
int rs = ps.executeUpdate();
if (rs==1){
flag = true;
}
return flag;
}
}

You should be import the DAO class package in servlet then access it it will work like
import DAO.cartDao;
If you will not import then how to acces it

I don't understand exactly what is not working? But I have noticed, you're not closing statement and the database connection in your DAO class.
FYI: An example
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
conn = // Retrieve connection
stmt = conn.prepareStatement(// Some SQL);
rs = stmt.executeQuery();
} catch(Exception e) {
// Error Handling
} finally {
try { if (rs != null) rs.close(); } catch (Exception e) {};
try { if (stmt != null) stmt.close(); } catch (Exception e) {};
try { if (conn != null) conn.close(); } catch (Exception e) {};
}

SQLException Operation not allowed after ResultSet closed

I am attempting to write a JUnit test for a query which is retrieved via a textbox in an html form. The text retrieval has been tested and works but my unit test is failing. I am using 2 relevant classes: QueryController and QueryControllerTest. I have been playing around with when and what I am closing in these two classes and keep getting the error: Operation not allowed after ResultSet closed.
QueryControllerTest.java
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.junit.Test;
import static org.junit.Assert.*;
public class QueryControllerTest {
#Test
public void testQuery() {
ResultSet testRs = null;
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
String connectionUrl = "jdbc:mysql://localhost:3306/test";
String connectionUser = "root";
String connectionPassword = "GCImage";
conn = DriverManager.getConnection(connectionUrl,
connectionUser, connectionPassword);
Query testQuery = new Query();
testQuery
.setQuery("select * from service_request where FN_contact = 'Greg'");
testRs = QueryController.executeSelect(conn, testQuery);
assertEquals("Laughlin", testRs.getString("LN_contact"));
assertEquals("Hello World", testRs.getString("Notes"));
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
testRs.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
QueryController.java
import java.util.Map;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
#Controller
public class QueryController {
#RequestMapping(value = "/query")
public String processRegistration(#ModelAttribute("query") Query query,
Map<String, Object> model) {
String queryString = query.getQuery();
if (queryString != null && !queryString.isEmpty()) {
System.out.println("query (from controller): " + queryString);
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
String connectionUrl = "jdbc:mysql://localhost:3306/test";
String connectionUser = "root";
String connectionPassword = "GCImage";
conn = DriverManager.getConnection(connectionUrl,
connectionUser, connectionPassword);
if (queryString.toLowerCase().startsWith("select")) {
ResultSet rs = executeSelect(conn, query);
} else {
int rowsUpdated = executeUpdate(conn, query);
System.out.println(rowsUpdated + " rows updated");
}
} catch (Exception e) {
e.printStackTrace();
}
}
return "query";
}
public static ResultSet executeSelect(Connection conn, Query query) {
ResultSet rs = null;
Statement stmt = null;
try {
stmt = conn.createStatement();
rs = stmt.executeQuery(query.getQuery());
while (rs.next()) {
String id = rs.getString("ID");
String firstName = rs.getString("FN_Contact");
String lastName = rs.getString("LN_Contact");
String notes = rs.getString("Notes");
System.out.println("ID: " + id + ", First Name: " + firstName
+ ", Last Name: " + lastName + ", Notes: " + notes);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if(rs!=null){
rs.close();
}
if(stmt != null){
stmt.close();
}
if (conn != null)
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
return rs;
}
}

QueryController.executeSelect is calling rs.close(), but then your assertEquals in QueryControllerTest.testQuery are calling methods on testRS. As executeSelect is returning the resultset, closing it first doesn't make sense. Further, executeSelect is being passed the connection, so it shouldn't be closing that either (what happens if the caller wants to do two different selects on the same connection?).

I think the problem is because you are creating two connections. Try to only instantiate the connection of QueryController class for your test. You will need to provide the connection. After you store it in a variable to run the query.
Connection con = QueryController.getConnection ();

Linking JComboBox with SQL

I am writing a code to make a list in JComboBox using the data in the database.
It's actually for a POS system, where i have to select an item from a list in the database..
Here is the code i have been trying:
(i did take try it without the while(itemsList != null) .. but it didnt work either
private class ButtonHandlerSales implements ActionListener
{
public final String userName = "root";
private final String password = "";
private final String serverName = "localhost";
private final int portNumber = 3306;
private final String dbName = "alphapos";
public void actionPerformed(ActionEvent action)
{
Connection conn = null;
try
{
conn = this.getConnection();
}
catch (SQLException e1)
{
e1.printStackTrace();
}
//System.out.println("Connected to database");
while(itemsList != null)
{
String[] list= null;
String command = "SELECT itemName FROM item";
try
{
list = viewTable(conn, command);
}
catch (SQLException e)
{
e.printStackTrace();
}
itemList = new JComboBox(list);
}
}
private String[] viewTable(Connection con, String command) throws SQLException
{
String list[] = null;
Statement stmt = null;
try
{
stmt = con.createStatement();
ResultSet rs = stmt.executeQuery(command);
int i=0;
while (rs.next())
{
list[i] = rs.getString("itemName");
i++;
}
}
catch (SQLException e )
{
e.printStackTrace();
}
finally
{
if (stmt !=
null) { stmt.close(); }
}
return list;
}
private Connection getConnection() throws SQLException
{
Connection conn = null;
Properties connectionProps = new Properties();
connectionProps.put("user", this.userName);
connectionProps.put("password", this.password);
conn = DriverManager.getConnection("jdbc:mysql://"
+ this.serverName + ":" + this.portNumber + "/" + this.dbName,
connectionProps);
return conn;
}
}//end of class
I'm not getting any errors.. the code compiles.. but im not getting any output (list is empty)..
Am i doing something wrong here?
Any help is really appreciated... ( im not looking for straight up codes )

Problem 1
In your viewTable method String list[] = null;. You never initialize it with a new String[..]. So you will new a NullPointerException. But it would be better to use an ArrayList, since you may not know exactly how many values will be returned
private List<String> viewTable(Connection con, String command) {
List<String> list = new ArrayList<>();
...
while (rs.next()) {
list.add(rs.getString("itemName"));
}
return list;
}
Problem 2
You are creating the JComboBox in the ActionListener. So you can't add the combo before the action is performed. With combo boxes, it's preferred to work with it's model, rather then the component, when working with the data. JComboBox has a ComboBoxModel. We can use the concrete DefaultComboBoxModel. You can pass an array to its constructor. List, has the method toArray we can call to create an array from the List. Then just pass the array to the DefaultComboBoxModel constructor and call the combo box setModel
List<String> list = null;
String command = "SELECT itemName FROM item";
try {
list = viewTable(conn, command);
} catch (SQLException e) {
e.printStackTrace();
}
ComboBoxModel model = new DefaultComboBoxModel(list.toArray());
itemList.setModel(model);
This way, you can initialize the combo box before the action is performed.
Update
If you want the combo box loaded on application start up, I don't see what the problem is. Just create a method in you class, using the code in the actionPerformed. Then just call that method, like in your main constructor or something. Maybe you could do something like below, where you have the method return a ComboBoxModel and you can use to set the model for the combo box
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.ComboBoxModel;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
public class Test {
private final JComboBox itemList;
public Test() throws SQLException {
itemList = new JComboBox(viewTable(getConnection(), command));
JButton button = new JButton("Populate");
button.addActionListener(new ButtonHandler());
JPanel panel = new JPanel(new GridLayout(0, 1));
panel.add(itemList);
panel.add(button);
JOptionPane.showMessageDialog(null, panel);
}
private class ButtonHandler implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
try {
ComboBoxModel model = viewTable(getConnection(), command);
itemList.setModel(model);
} catch (SQLException ex) {
Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
public static void main(String[] args) throws SQLException {
Test test = new Test();
}
private ComboBoxModel viewTable(Connection con, String command) throws SQLException {
List<String> list = new ArrayList<>();
try (Statement stmt = con.createStatement()) {
ResultSet rs = stmt.executeQuery(command);
while (rs.next()) {
list.add(rs.getString("itemName"));
}
} catch (SQLException e) {
e.printStackTrace();
}
return new DefaultComboBoxModel(list.toArray());
}
public final String userName = "root";
private final String password = "";
private final String serverName = "localhost";
private final int portNumber = 3306;
private final String dbName = "alphapos";
private final String command = "select itemName from item";
private Connection getConnection() throws SQLException {
Connection conn = null;
Properties connectionProps = new Properties();
connectionProps.put("user", this.userName);
connectionProps.put("password", this.password);
conn = DriverManager.getConnection("jdbc:mysql://"
+ this.serverName + ":" + this.portNumber + "/" + this.dbName,
connectionProps);
return conn;
}
}

Mysql database Exception

Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Type mismatch: cannot convert from java.sql.Statement to com.mysql.jdbc.Statement
i am a beginner in java i am trying to use mysql database i have downloaded mysql-connector-java-5.1.23-bin.jar file from mysql.com and i have added this jar file to in my build path of my project but there is an error in the following code
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
Type mismatch: cannot convert from java.sql.Statement to com.mysql.jdbc.Statement
package com.example.demo;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;
public class DBConnect
{
private static final String userName = "root";
private static final String userpwd = "sverma";
private static final String CONN_STR = "jdbc:mysql://localhost:3306/phpweb_db";
public static void main(String[] args) throws SQLException
{
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try
{
DriverManager.getConnection(CONN_STR, userName, userpwd);
st=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
rs = st.executeQuery("select * from user");
rs.last();
System.out.println("No of rows: " + rs.getRow());
// System.out.println("Connected Successfully...");
}
catch (SQLException e)
{
System.err.println(e);
}
finally
{
if (rs != null)
{
rs.close();
}
if (st != null)
{
st.close();
}
if (conn != null)
{
conn.close();
}
}
}
}

Wrong classes
import com.mysql.jdbc.Connection;
import com.mysql.jdbc.Statement;
should be
import java.sql.Connection;
import java.sql.Statement;
In fact, java decouples everything from a specific database engine. One never should need an import of MySQL (or ProgressSQL or ...) classes.
To have those classes available at run-time, the first thing after the try, before getting the connection would be:
Class.forName("com.mysql.jdbc.Driver");
This technique would allow reading all strings from a configuration file, and writing database independent code.
Missing: conn = ...
conn = DriverManager.getConnection(CONN_STR, userName, userpwd);

package com.example.demo;
import java.sql.*;
public class DBConnect
{
private static final String userName = "root";
private static final String userpwd = "sverma";
private static final String CONN_STR = "jdbc:mysql://localhost:3306/phpweb_db";
public static void main(String[] args) throws SQLException
{
Connection conn;
Statement st;
ResultSet rs;
try
{
Class.forName("com.mysql.jdbc.Driver");
DriverManager.getConnection(CONN_STR, userName, userpwd);
st=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
rs = st.executeQuery("select * from user");
rs.last();
System.out.println("No of rows: " + rs.getRow());
// System.out.println("Connected Successfully...");
}
catch (SQLException e)
{
System.err.println(e);
}
finally
{
if (rs != null)
{
rs.close();
}
if (st != null)
{
st.close();
}
if (conn != null)
{
conn.close();
}
}
}