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JDBC SQL Server errors: ClassNotFound & Not Suitable Driver Found

I am very new to Java and am simply trying to connect to my MSSQL database and return a list of customers. When I try the JDBC connection, I get a "no suitable driver found" error. When I add a Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver") statement, I get a ClassNotFound error. This seems like it should be a lot easier than it's turning out to be. Please help me either find a suitable driver or how to get access through the Class.forName usage.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.sql.Statement;
public class DbConn {
public static String getConnString(){
return "jdbc:sqlserver://localhost\\SQLEXPRESS:1433;database=OhHold;";
}
public static void getConnection() {
try
{
//Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
String user = "<USER>";
String pw = "****************";
Connection connection = DriverManager.getConnection(getConnString(), user, pw);
Statement statement = connection.createStatement();
String sql = "select txtCompanyName as company from tblCustomers where intNotActive <> 1";
ResultSet result = statement.executeQuery(sql);
while (result.next()) {
System.out.println(result.getString(1));
}
}
/*
// Handle any errors that may have occurred.
catch (ClassNotFoundException e) {
e.printStackTrace();
}
*/
catch (SQLException ex) {
ex.printStackTrace();
}
}
public static void main(String[] args) {
getConnection();
}
}

Referring to a variable from outside static Connection method [duplicate]

This question already has answers here:
Non-static variable cannot be referenced from a static context
(15 answers)
Closed 1 year ago.
I am new to java and started doing a javaFX project. In this project, I receive a variable from a previous frame, and use it to execute an SQL query in order to render the table based on that particular variable.
Here is my code:
package financials;
import java.net.URL;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ResourceBundle;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
import javax.swing.JOptionPane;
/**
* FXML Controller class
*
* #author param
*/
public class theControl implements Initializable {
#FXML
private Label test;
/**
* Initializes the controller class.
*/
#Override
public void initialize(URL url, ResourceBundle rb) {
Statement st;
Connection con = null;
}
/**
*
* #param name
*/
public void previous(String name) {
System.out.println(name);
}
public static Connection ConnectDB() {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost/database", "root", "Password");
return con;
} catch(Exception ae) {
JOptionPane.showMessageDialog(null, ae);
return null;
}
}
public static ObservableList<RenderNow> getListAccount() {
Connection con = ConnectDB();
ObservableList<RenderNow> list = FXCollections.observableArrayList();
try {
PreparedStatement pst = con.prepareStatement("SELECT * FROM lines WHERE Code=? ");
pst.setString(1, name); //This is where I am having trouble
ResultSet rs = pst.executeQuery();
while (rs.next()) {
list.add(new SBRender(rs.getString("Account1"), rs.getString("Account2"), rs.getString("Account3"), rs.getString("Account4"), rs.getString("Account5")));
}
} catch(Exception ae) {
JOptionPane.showMessageDialog(null, ae);
return null;
}
return list;
}
}
The problem is that the variable name is not being recognized in the pst.setString line. The error I am getting is that variable 'name' is not found. I tried a different approach where I used name to set the text of Label test, and then later tried to get the variable in the public static Connection ConnectDB() method.
Something like:
public class theControl implements Initializable {
#FXML
private Label test;
/**
* Initializes the controller class.
*/
#Override
public void initialize(URL url, ResourceBundle rb) {
Statement st;
Connection con = null;
}
/**
*
* #param name
*/
public void previous(String name) {
System.out.println(name);
test.setText(name); //Where i set the text of label 'text'
}
public static Connection ConnectDB() {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost/database", "root", "Password");
return con;
} catch(Exception ae) {
JOptionPane.showMessageDialog(null, ae);
return null;
}
}
public static ObservableList<RenderNow> getListAccount() {
String name2 = test.getText(); //Where I try and get the text from label 'text'
Connection con = ConnectDB();
ObservableList<RenderNow> list = FXCollections.observableArrayList();
try {
PreparedStatement pst = con.prepareStatement("SELECT * FROM lines WHERE Code=? ");
pst.setString(1, name2); //This is where I am having trouble
ResultSet rs = pst.executeQuery();
while (rs.next()) {
list.add(new SBRender(rs.getString("Account1"), rs.getString("Account2"), rs.getString("Account3"), rs.getString("Account4"), rs.getString("Account5")));
}
} catch(Exception ae) {
JOptionPane.showMessageDialog(null, ae);
return null;
}
return list;
}
}
However, this attempt returns an error non-static variable test cannot be referenced from a static context. My understanding is that since the label test is not static, static Connection is unable to get the text. Is there any work around for this ?

In your first case, the variable was not set. It's only available on the method where you have your print method.
In the second case, you are not using the object. The test variable is in one object, so not accessible by static method which are not depending of object.
I suggest you to ad new parameter to your static method, and use like this:
// create new static method which require the name in parameters
public static ObservableList<RenderNow> getListAccountWithName(String name) {
Connection con = ConnectDB(); // get DB thanks to static method
ObservableList<RenderNow> list = FXCollections.observableArrayList();
try {
PreparedStatement pst = con.prepareStatement("SELECT * FROM lines WHERE Code = '?'");
pst.setString(1, name); // now you can use name value
ResultSet rs = pst.executeQuery();
while (rs.next()) {
list.add(new SBRender(rs.getString("Account1"), rs.getString("Account2"), rs.getString("Account3"), rs.getString("Account4"), rs.getString("Account5")));
}
} catch(Exception ae) {
JOptionPane.showMessageDialog(null, ae);
return null;
}
return list;
}
And now, you can call it from the object like:
ObservableList<RenderNow> accounts = getListAccountWithName(test.getText());
// now what you have what you are looking for

Open CSV Performance to write data

I came through a link: https://github.com/hyee/OpenCSV which drastically improves the writing time of the JDBC ResultSet to CSV due to setAsyncMode, RESULT_FETCH_SIZE
//Extract ResultSet to CSV file, auto-compress if the fileName extension is ".zip" or ".gz"
//Returns number of records extracted
public int ResultSet2CSV(final ResultSet rs, final String fileName, final String header, final boolean aync) throws Exception {
try (CSVWriter writer = new CSVWriter(fileName)) {
//Define fetch size(default as 30000 rows), higher to be faster performance but takes more memory
ResultSetHelperService.RESULT_FETCH_SIZE=10000;
//Define MAX extract rows, -1 means unlimited.
ResultSetHelperService.MAX_FETCH_ROWS=20000;
writer.setAsyncMode(aync);
int result = writer.writeAll(rs, true);
return result - 1;
}
}
But the problem is I don't know how I can merge above into my requirement. As the link has many other classes involved which I am not sure what they do and if I even need it for my requirement. Still, I tried but it fails to compile whenever I enable 2 commented line code. Below is my code.
Any help on how I can achieve this will be greatly appreciated.
package test;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Date;
import com.opencsv.CSVWriter;
import com.opencsv.ResultSetHelperService;
public class OpenCSVTest1
{
static Connection con =null;
static Statement stmt = null;
static ResultSet rs = null;
public static void main(String args[]) throws Exception
{
connection ();
retrieveData(con);
}
private static void connection() throws Exception
{
try
{
Class.forName("<jdbcdriver>");
con = DriverManager.getConnection("jdbc:","<username>","<pass>");
System.out.println("Connection successful");
}
catch (Exception e)
{
System.out.println("Exception while establishing sql connection");
throw e;
}
}
private static void retrieveData(Connection con) throws Exception
{
try
{
stmt=con.createStatement();
stmt = con.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
String query = "SELECT * FROM dbo.tablename";
rs=stmt.executeQuery(query);
CSVWriter writer = new CSVWriter(new BufferedWriter(new FileWriter("C:\\Data\\File1.csv")));
ResultSetHelperService service = new ResultSetHelperService();
/*** ResultSetHelperService.RESULT_FETCH_SIZE=10000; ***/ // to add
service.setDateTimeFormat("yyyy-MM-dd HH:mm:ss.SSS");
System.out.println("**** Started writing Data to CSV **** " + new Date());
writer.setResultService(service);
/*** writer.setAsyncMode(aync); ***/ // to add
int lines = writer.writeAll(rs, true, true, false);
writer.flush();
writer.close();
System.out.println("** OpenCSV -Completed writing the resultSet at " + new Date() + " Number of lines written to the file " + lines);
}
catch (Exception e)
{
System.out.println("Exception while retrieving data" );
e.printStackTrace();
throw e;
}
finally
{
rs.close();
stmt.close();
con.close();
}
}
}
UPDATE
I have updated my code. Right now code is writing complete resultset in CSV at once using writeAll method which is resulting in time consumption.
Now what I want to do is write resultset to CSV in batches as resultset's first column will always have dynamically generated via SELECT query Auto Increment column (Sqno) with values as (1,2,3..) So not sure how I can read result sets first column and split it accoridngly to write in CSV. may be HashMap might help, so I have also added resultset-tohashmap conversion code if required.
import com.opencsv.CSVWriter;
import com.opencsv.ResultSetHelperService;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class OpenCSVTest1
{
static int fetchlimit_src = 100;
static Connection con =null;
static Statement stmt = null;
static ResultSet rs = null;
static String filename = "C:\\Data\\filename.csv";
static CSVWriter writer;
public static void main(String args[])
{
try
{
connection();
retrieveData(con);
}
catch(Exception e)
{
System.out.println(e);
}
}
private static void connection() throws Exception
{
try
{
Class.forName("<jdbcdriver>");
con = DriverManager.getConnection("jdbc:","<username>","<pass>");
System.out.println("Connection successful");
}
catch (Exception e)
{
System.out.println("Exception while establishing sql connection");
throw e;
}
}
private static void retrieveData(Connection con) throws Exception
{
try
{
stmt=con.createStatement();
String query = "SELECT ROWNUM AS Sqno, * FROM dbo.tablename "; // Oracle
// String query = "SELECT ROW_NUMBER() OVER(ORDER BY Id ASC) AS Sqno, * FROM dbo.tablename "; // SQLServer
System.out.println(query);
stmt = con.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
stmt.setFetchSize(fetchlimit_src);
System.out.println("**** Started querying src **** " + new Date());
rs=stmt.executeQuery(query);
System.out.println("**** Completing querying src **** " + new Date());
// resultset_List(rs); // If required store resultset(rs) to HashMap
writetoCSV(rs,filename);
/** How to write resultset to CSV in batches instead of writing all at once to speed up write performance ?
* Hint: resultset first column is Autoincrement [Sqno] (1,2,3...) which might help to split result in batches.
*
**/
}
catch (Exception e)
{
System.out.println("Exception while retrieving data" );
e.printStackTrace();
throw e;
}
finally
{
rs.close();
stmt.close();
con.close();
}
}
private static List<Map<String, Object>> resultset_List(ResultSet rs) throws SQLException
{
ResultSetMetaData md = rs.getMetaData();
int columns = md.getColumnCount();
List<Map<String, Object>> rows = new ArrayList<Map<String, Object>>();
while (rs.next())
{
Map<String, Object> row = new HashMap<String, Object>(columns);
for(int i = 1; i <= columns; ++i)
{
row.put(md.getColumnName(i), rs.getObject(i));
}
rows.add(row);
}
// System.out.println(rows.toString());
return rows;
}
private static void writetoCSV(ResultSet rs, String filename) throws Exception
{
try
{
writer = new CSVWriter(new BufferedWriter(new FileWriter(filename)));
ResultSetHelperService service = new ResultSetHelperService();
service.setDateTimeFormat("yyyy-MM-dd HH:mm:ss.SSS");
long batchlimit = 1000;
long Sqno = 1;
ResultSetMetaData rsmd = rs.getMetaData();
String columnname = rsmd.getColumnLabel(1); // To retrieve columns with labels (for example SELECT ROWNUM AS Sqno)
System.out.println("**** Started writing Data to CSV **** " + new Date());
writer.setResultService(service);
int lines = writer.writeAll(rs, true, true, false);
System.out.println("** OpenCSV -Completed writing the resultSet at " + new Date() + " Number of lines written to the file " + lines);
}
catch (Exception e)
{
System.out.println("Exception while writing data" );
e.printStackTrace();
throw e;
}
finally
{
writer.flush();
writer.close();
}
}
}

You should be able to use the OpenCSV sample, pretty much exactly as it is provided in the documentation. So, there should be no need for you to write any of your own batching logic.
I was able to write a 6 million record result set to a CSV file in about 10 seconds. To be clear -that was just the file-write time, not the DB data-fetch time - but I think that should be fast enough for your needs.
Here is your code, with adaptations for using OpenCSV based on its documented approach... But please see the warning at the end of my notes!
import com.opencsv.CSVWriter;
import com.opencsv.ResultSetHelperService;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Date;
import java.text.SimpleDateFormat;
public class OpenCSVDemo {
static int fetchlimit_src = 100;
static Connection con = null;
static Statement stmt = null;
static ResultSet rs = null;
static String filename = "C:\\Data\\filename.csv";
public static void main(String args[]) {
try {
connection();
retrieveData(con);
} catch (Exception e) {
System.out.println(e);
}
}
private static void connection() throws Exception {
try {
final String jdbcDriver = "YOURS GOES HERE";
final String dbUrl = "YOURS GOES HERE";
final String user = "YOURS GOES HERE";
final String pass = "YOURS GOES HERE";
Class.forName(jdbcDriver);
con = DriverManager.getConnection(dbUrl, user, pass);
System.out.println("Connection successful");
} catch (Exception e) {
System.out.println("Exception while establishing sql connection");
throw e;
}
}
private static void retrieveData(Connection con) throws Exception {
try {
stmt = con.createStatement();
String query = "select title_id, primary_title from imdb.title";
System.out.println(query);
stmt = con.createStatement(ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
stmt.setFetchSize(fetchlimit_src);
System.out.println("**** Started querying src **** " + new Date());
rs = stmt.executeQuery(query);
System.out.println("**** Completing querying src **** " + new Date());
// resultset_List(rs); // If required store resultset(rs) to HashMap
System.out.println();
String timeStamp = new SimpleDateFormat("yyyy.MM.dd.HH.mm.ss").format(new Date());
System.out.println("Started writing CSV: " + timeStamp);
writeToCsv(rs, filename, null, Boolean.FALSE);
timeStamp = new SimpleDateFormat("yyyy.MM.dd.HH.mm.ss").format(new Date());
System.out.println("Finished writing CSV: " + timeStamp);
System.out.println();
} catch (Exception e) {
System.out.println("Exception while retrieving data");
e.printStackTrace();
throw e;
} finally {
rs.close();
stmt.close();
con.close();
}
}
public static int writeToCsv(final ResultSet rs, final String fileName,
final String header, final boolean aync) throws Exception {
try (CSVWriter writer = new CSVWriter(fileName)) {
//Define fetch size(default as 30000 rows), higher to be faster performance but takes more memory
ResultSetHelperService.RESULT_FETCH_SIZE = 1000;
//Define MAX extract rows, -1 means unlimited.
ResultSetHelperService.MAX_FETCH_ROWS = 2000;
writer.setAsyncMode(aync);
int result = writer.writeAll(rs, true);
return result - 1;
}
}
}
Points to note:
1) I used "async" set to false:
writeToCsv(rs, filename, null, Boolean.FALSE);
You may want to experiment with this and the other settings to see if they make any significant difference for you.
2) Regarding your comment "the link has many other classes involved": The OpenCSV library's entire JAR file needs to be included in your project, as does the related disruptor JAR:
opencsv.jar
disruptor-3.3.6.jar
To get the JAR files, go to the GitHub page, click on the green button, select the zip download, unzip the zip file, and look in the "OpenCSV-master\release" folder.
Add these two JARs to your project in the usual way (depends on how you build your project).
3) WARNING: This code runs OK when you use Oracle's Java 8 JDK/JRE. If you try to use OpenJDK (e.g. for Java 13 or similar) it will not run. This is because of some changes behind the scenes to hidden classes. If you are interested, there are more details here.
If you need to use an OpenJDK version of Java, you may therefore have better luck with the library on which this CSV library is based: see here.

com.mysql.jdbc.exception.jdbc4.MySQLNonTransientConnectionException: No operation allowed after connection closed

how to solve this problem and what is wrong in this code?
i know that the question has been asked before but i cant solve the problem
private void cb_categoriesPopupMenuWillBecomeVisible(javax.swing.event.PopupMenuEvent evt) {
cb_categories.removeAllItems();
try {
String sql_c = "SELECT * FROM inventory.categories";
cc.pst = cc.c.prepareStatement(sql_c);
cc.rs = cc.pst.executeQuery();
while (cc.rs.next()) {
String c_name = cc.rs.getString("CategoryName");
cb_categories.addItem(c_name);
}
} catch (Exception e) {
JOptionPane.showMessageDialog(null, e);
} finally {
try {
cc.rs.close();
cc.pst.close();
} catch (Exception e) {
}
}
}

Your ResultSet and PreparedStatement are not declared in method scope, so I have to assume that you've declared them elsewhere.
That's a big mistake.
You should declare the Statement and ResultSet in method scope.
You make an attempt to close your resources, but you should wrap them in individual try/catch blocks. You cannot risk one being closed and not the other.
There are other things I'd criticize about your code (e.g. SELECT *, mingling UI and database code together in a single class), but that's enough to start.
Start with an interface:
package persistence;
import java.util.List;
/**
* Created by Michael
* Creation date 8/20/2017.
* #link https://stackoverflow.com/questions/45787151/com-mysql-jdbc-exception-jdbc4-mysqlnontransientconnectionexception-no-operatio/45787321?noredirect=1#comment78532554_45787321
*/
public interface CategoryDao {
List<String> findAllCategories();
}
Then write a concrete implementation:
package database;
import database.util.DatabaseUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import javax.sql.DataSource;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
/**
* Created by Michael
* Creation date 8/20/2017.
* #link https://stackoverflow.com/questions/45787151/com-mysql-jdbc-exception-jdbc4-mysqlnontransientconnectionexception-no-operatio/45787321?noredirect=1#comment78532554_45787321
*/
public class CategoryDaoImpl implements CategoryDao {
private static final Log LOGGER = LogFactory.getLog(CategoryDaoImpl.class);
private static String SELECT_CATEGORIES = "SELECT CategoryName from inventory.Categories ";
private DataSource dataSource;
public CategoryDaoImpl(DataSource dataSource) {
this.dataSource = dataSource;
}
#Override
public List<String> findAllCategories() {
List<String> categories = new ArrayList<>();
PreparedStatement ps = null;
ResultSet rs = null;
try {
ps = this.dataSource.getConnection().prepareStatement(SELECT_CATEGORIES);
rs = ps.executeQuery();
while (rs.next()) {
categories.add(rs.getString("CategoryName"));
}
} catch (SQLException e) {
LOGGER.error(String.format("Exception caught while selecting all category names"), e);
} finally {
DatabaseUtils.close(rs);
DatabaseUtils.close(ps);
}
return categories;
}
}
This is something that you can test with JUnit off to the side. Get it running perfectly, then give a reference to your UI code. It'll keep the UI and database code separate. You can use this DAO in any application without worrying about Swing or web UI.

Constructing and object of a class and calling it's methode in Java

Trying to program that can read a MySql database. Somehow I cannot call the methode connect(). It says:
Error: cannot find symbol"
connect.connnect();
_______^
What I'm trying to do is to have the connnect and getData method in different classes, so I can also use the connect class seperately for other projects.
Main:
import java.sql.*;
public class Main {
public static void main( String argv[]) {
Connect connect = new Connect();
Connect.connect();
GetData getdata = new GetData();
getdata.getdata();
}
}
Connect:
import java.sql.*;
public class Connect{
public Connection con;
public Statement st;
public ResultSet rs;
public connect(){
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/leichtathletik","root","");
st = con.createStatement();
}catch(Exception e1) {
System.out.println("Error: "+e1);
}
}
}
GetData:
import java.sql.*;
public class GetData {
public void getData() {
try {
String query = "select * läufer";
rs = st.esecuteQuery(query);
while (rs.next()) {
String vorname = rs.getString("vorname");
String nachname = rs.getString("nachname");
System.out.println(vorname+" "+nachname);
} // end of while
} catch(Exception e2) {
System.out.println("Error: "+e2);
}
}
}

The "connect"- method on the Connect class needs to have a type.
https://docs.oracle.com/javase/tutorial/java/javaOO/methods.html , can be helpful.
Further more, the youtuber (https://www.youtube.com/channel/UCiczh_Q-rC7VhMV0x6__dBw) can maybe help you get started with java.