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Java JDBC: Cannot insert Data into Database

I'm coding for hours to insert data into my SQL database, but nothing happens.
I even can't debug Java, because I don't get any output of my console.
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.PreparedStatement;
import java.text.DecimalFormat;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
*
* #author xxx
*/
public class MyServlet extends HttpServlet {
private static final String URL = "jdbc:mysql://localhost:3306/userdata";
private static final String USER = "root";
private static final String PASSWORD = "root";
private static final DecimalFormat DF2 = new DecimalFormat("#.##");
private static Connection con;
private static Statement stmt;
private static ResultSet rs;
protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter()) {
try {
String myDriver = "com.mysql.jdbc.Driver";
try {
Class.forName(myDriver);
// opening database connection to MySQL server
con = DriverManager.getConnection(URL, USER, PASSWORD);
// getting Statement object to execute query
// the mysql insert statement
String query = "INSERT INTO customers (customer, currency, amount) values ('Name', 'Currency', 100);";
stmt.executeUpdate(query);
// execute the preparedstatement
// executing SELECT query
rs = stmt.executeQuery(query);
con.close();
stmt.close();
rs.close();
} catch (SQLException sqlEx) {
sqlEx.printStackTrace();
}
}
}
}
What did I wrong, that nothing happens? Even if I use this code for Java-Classes (not Servlets), I only receive an compile error, but without message.
I'm using the IDE Netbeans and mysql DB is the MySQL Workbench. The Java Class is using the main method.
Update:
I've tested following Code with IntelliJ:
import java.sql.*;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Main {
public static void main(String[] args) {
String url = "jdbc:mysql://localhost:3306/userdata";
String user = "root";
String password = "root";
String query = "Insert into customers (customer, currency, amount) values('Michael Ballack', 'Euro', 500)";
try (Connection con = DriverManager.getConnection(url, user, password);
PreparedStatement pst = con.prepareStatement(query)) {
pst.executeUpdate();
} catch (SQLException ex) {
Logger lgr = Logger.getLogger(JdbcMySQLVersion.class.getName());
lgr.log(Level.SEVERE, ex.getMessage(), ex);
}
}
private static class JdbcMySQLVersion {
public JdbcMySQLVersion() {
}
}
I can insert data into the MySQL database.
In Netbeans this code won't work, although I've implemented the MySQLConnector. I don't know why, but Netbeans seems hard to handle.

In the servlet code, I don't see you ever write anything to out. So nothing is being sent back to the browser, even if it compiled. You could write your SQL exception to the out writer you created. To be more precise add this in your exception: out.println(sqlEx.printStackTrace()); That should at least show what exception you are getting back to the browser.
What is the compile error you get outside of a servlet?
This maybe obvious, but to get JDBC stuff to work on your server, you need to have the MySQL server installed, started and configured. The table referenced has to be defined, etc. You could check this outside of the Java servlet environment with the tools provided with MySQL.

your code can not compile, you miss catch exception for second 'try'.
Where do you use this class to run, if you run a java class, this class must contain main() function?
you should use some IDEs like eclipse or IntelliJ to code, it help you detect the error easier.

I found the solution. If you are using Netbeans with the Glassfish-Server and you want your servlet to save data into the database, you have to make sure that Netbeans has installed the Driver of your Database Connector (e.g. MySQL Connector). But you also have to configurate your server (e.g. Glassfish) which will support the DB Connector drivers.
In my case my Server didn't load the DB Connector Driver so the JDBC Code couldn't be executed.
Here's a useful link to configurate the Glassfish Server: https://dzone.com/articles/nb-class-glassfish-mysql-jdbc

Servlet to mysql jdbc connection class not found exception

I am trying to connect servlet to mysql database in netbeans 8 and jdk 8 and glassfish server. i have also included mysqlconnector jar file in libraries but am getting
class not found exception at Class.forName("com.mysql.jdbc.Driver")
piece of my code
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;
public class sqltest1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String user = request.getParameter("user");
String pass = request.getParameter("pass");
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/demo", "root", "root");
PreparedStatement pst = conn.prepareStatement("Select user,pass from login where user=? and pass=?");
pst.setString(1, user);
pst.setString(2, pass);
ResultSet rs = pst.executeQuery();
if (rs.next()) {
out.println("Correct login credentials");
}
else {
out.println("Incorrect login credentials");
}
}
}

Try reAdding jar file into java build path and clean than recompile.
Your code looks fine.

Check mysql driver jar on your classpath and also verify proper mysql driver jar.

Android-MysqlConnectivity in eclipse

I am new to android, So i need a basic knowledge,How to connect to the database and Select some of the values from it.
These are all the following steps i have already completed by watching and reading some online tutorials.
Created a New ANDROID Project Named And2.
Created a New JAVA Project named MYSQLConnection which is used to store the database connection.
I have Downloaded mysql-connector-java-5.1.34 file Online and added it.
I have attached the Screen Shot the total overview of my eclipse.
Now i just needed to access the database in And2 and Write a Simple Select Query So that i can make sure that connection is created.
Shown below is the Java file for DB Connection.
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Connection;
import java.sql.Statement;
import com.mysql.jdbc.*;
//import com.mysql.jdbc.Connection;
//import com.mysql.jdbc.Statement;
public class Main {
public static void main(String[] args) throws Exception
{
Class.forName("com.mysql.jdbc.Driver");
try
{
String connectionUrl = "jdbc:mysql://localhost:3306/testdatabase";
String connectionUser = "root";
String connectionPassword = "12345";
Connection conn = DriverManager.getConnection(connectionUrl, connectionUser,
connectionPassword);
//Statement stmt = conn.createStatement();
// ResultSet reset = stmt.executeQuery("select * from TableName");
//
// //Print the data to the console
// while(reset.next()){
// Log.w("Data:",reset.getString(3));
//
// }
}
catch ( SQLException err )
{
System.out.println("Database connection failed");
}
}
}
Any Help appreciated.

JDBC Connection Error to Oracle Database

I'm trying to establish a connection from Java to Oracle DB. (My DB is in another machine)
The form of URL as i know is like : String url = "jdbc:oracle:thin:#hostname:portnumber:sid";
And here is my Java code to establish a connection:
package net.metric.action;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class DemoServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text");
PrintWriter out = response.getWriter();
System.out.println("-------- Oracle JDBC Connection Testing ------");
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
} catch (ClassNotFoundException e) {
System.out.println("Where is your Oracle JDBC Driver?");
e.printStackTrace();
return;
}
try{
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
//CONNECT TO DB
String url = "jdbc:oracle:thin:#252.112.60.47:1521:XE";
System.out.println(url);
Connection conn = DriverManager.getConnection(url,"EXT02501231","Tellcom30");
conn.setAutoCommit(false);
Statement stmt = conn.createStatement();
System.out.println("OK");
/* ResultSet rset =
stmt.executeQuery("select * from SBO_AUDIT_NEW.AUDIT_EVENT");
while (rset.next()) {
System.out.println (rset.getString(1));
}
stmt.close();
System.out.println ("Ok.");*/
}catch(Exception e){
System.out.println(e.getMessage());
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
}
I'm getting this error :
-------- Oracle JDBC Connection Testing ------
Io exception: The Network Adapter could not establish the connection
What am I doing wrong? Any answer would be appreciated..
Thanks

There are three ways to write to a jdbc url.
If you are connecting with service name you should put / before service name
jdbc:oracle:thin:#hostname:port/service_name --- In your case this is how you need the url
if you are connecting with sid you should put : before sid
jdbc:oracle:thin:#hostname:port:sid
or use the description in your tns file after #
jdbc:oracle:thin:#(DESCRIPTION=....)
BUT non of them are the cause for your problem. This error is not an SQLException. It is a TCP/IP connection exception. That means you somehow can not reach the machine.
Are you able to connect to the database with another client ? I see you are using TOAD. Are you able to connect with toad ? You need to make sure you can reach the server.
Try pinging to the machine on command line
ping 85.29.60.47
if you get response back then try telnet on the port
telnet 85.29.60.47 1521 -- You must have a telnet client installed to do that.
You will probably see either ping or telnet fails. So it is probably a firewall issue. What you need to do is to contact network administrators about the problem then.

Cannot connect to MS SQL SERVER

I have JBoss and MSSQL Server 2008. Sqljdbc.jar is in Java Resources/Libraries, but I still have a ClassNotFoundExeption.
This is my servlet :
package work.Model;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;
public class SQLServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public SQLServlet() {
super();
}
final String server = "localhost";
final int port = 1433;
final String user = "work";
final String password = "workdb";
final String database = "workDB";
final String jdbcUrl = "jdbc:sqlserver://"+server+":"+1433+";user="+user+";password="+password+";databaseName="+database+"";
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
try {
System.out.println("try to load driver");
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
System.out.println("# - Driver Loaded");
Connection con = DriverManager.getConnection(jdbcUrl);
System.out.println("# - Connection Obtained");
Statement stmt = con.createStatement();
System.out.println("# - Statement Created");
String loginCheck = "SELECT userID,username,password FROM USERS where username=? and password=?";
} catch (Exception ex) {
System.out.println("Error : "+ex);
}
}
}
The error is :
[STDOUT] Error : java.lang.ClassNotFoundException: com.microsoft.sqlserver.jdbc.SQLServerDriver from BaseClassLoader#724c0116{VFSClassLoaderPolicy#5bdb85f9{name=vfszip:/D:/Jboss/jboss-5.1.0.GA/server/default/deploy/Work.war/
How to correctly connect to MSSQL Server?

Try putting the SqlJdbc.jar in D:/Jboss/jboss-5.1.0.GA/server/default/lib folder and restart the server.

Servlets are used in the web application that has a predefined folder structure. As soon as you are not creating a deployment structure for JBoss server you have a chance to put JDBC driver jar to the WEB-INF/lib folder or copy it there during build.
Another approach is create a JBoss service that publish a datasource on JNDI and use its context and retrieve them on RAR deployment.