I am working on a GWT project in which I need to make some MySQL queries. I have handled RPC properly and in the server-side I am trying to make a mysql connection but am running into an exception:
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance_(Runtime.java:112)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance(Runtime.java:120)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2412)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2154)
at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:792)
at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance_(Runtime.java:112)
at com.google.appengine.tools.development.agent.runtime.Runtime.newInstance(Runtime.java:120)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
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I created a very simple java class to test out my code to confirm that my connection syntax and use is proper, and have confirmed that syntax is not a problem because with the very same code in a simple only main method java app I can create a connection and query the database properly. I have made sure to have mysql-connector-java-5.1.16-bin.jar in the classpath as well as the /lib folder in the WEB-INF folder.
Here is the class that I am using in order to create a connection:
public class DB_Connection {
protected Connection getConnection() {
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver").newInstance();
conn = DriverManager.getConnection("jdbc:mysql:///",
"",
"");
}
catch (Exception ex)
{
ex.printStackTrace();
}
return conn;
}
}
public class Login extends DB_Connection {
public User getUser(String email) {
User user = new User();
user.setUserEmail(email);
String query = "";
try {
Connection conn = getConnection();
Statement statement = conn.createStatement();
ResultSet result = statement.executeQuery(query);
while(result.next()) {
user.setUserId(result.getInt("rvuser_id"));
System.out.println(user.getUserId());
}
}
catch (Exception ex)
{
ex.printStackTrace();
}
return user;
}
It seems my problem happens all the way at the beginning in DB_Connection. Does anyone know what is making this happen? It is strange to me, because as a standalone the code works fine.
Another thing I just realized that I am at home now and don't even have access to that database server as it is on a local network and I am not connected through VPN. So it must be failing somehow before it even attempts to make the connection.
Thanks!
com.google.appengine ..
Does it means you are deploying on Google App Engine?
If so, MySQL,JDBC and many other things are restricted.
Related
This question already has answers here:
Connect Java to a MySQL database
(14 answers)
Closed 5 years ago.
ok so i have a java fx app that will display info from a mysql database runing locally on the same computer. i keep getting driver not found. here is the code:
String databaseURL = "jdbc:mysql://localhost:3307/mysql?zeroDateTimeBehavior=convertToNull";
String user = "user";
String password = "password";
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection(databaseURL, user, password);
if (conn != null) {
System.out.println("Connected to the database");
}
} catch (ClassNotFoundException ex) {
System.out.println("Could not find database driver class");
ex.printStackTrace();
} catch (SQLException ex) {
System.out.println("An error occurred. Maybe user/password is invalid");
ex.printStackTrace();
} finally {
if (conn != null) {
try {
conn.close();
} catch (SQLException ex) {
ex.printStackTrace();
}
}
and here is the stack trace:
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
at java.net.URLClassLoader$1.run(URLClassLoader.java:372)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:360)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:259)
at got_map.GOT_Map.start(GOT_Map.java:130)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$153(LauncherImpl.java:821)
at com.sun.javafx.application.LauncherImpl$$Lambda$51/1468396900.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$166(PlatformImpl.java:323)
at com.sun.javafx.application.PlatformImpl$$Lambda$44/584634336.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$164(PlatformImpl.java:292)
at com.sun.javafx.application.PlatformImpl$$Lambda$47/1960854798.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(PlatformImpl.java:291)
at com.sun.javafx.application.PlatformImpl$$Lambda$45/501263526.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$141(WinApplication.java:102)
at com.sun.glass.ui.win.WinApplication$$Lambda$37/96639997.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)
Apr 21, 2017 6:29:06 PM javafx.fxml.FXMLLoader$ValueElement processValue
WARNING: Loading FXML document with JavaFX API of version 8.0.111 by JavaFX runtime of version 8.0.20
Any help would be much appreciated
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
...
at java.lang.Class.forName(Class.java:259)
at got_map.GOT_Map.start(GOT_Map.java:130)
This : Class.forName("com.mysql.jdbc.Driver"); is not enough.
Indeed, it rises a ClassNotFoundException if the class cannot be retrieved from the runtime classpath.
You need just to add in the runtime classpath the MySQL JDBC driver matching with the installed MySQL version.
The problem is in the line, Class.forName("com.mysql.jdbc.Driver");
The reason for getting java.lang.ClassNotFoundException can be an issue in loading the driver.Add the *.jar driver to your project if you haven't added it.
I am getting the following exception :-
java.sql.SQLException: [DataDirect][OpenEdge JDBC Driver][OpenEdge] Access denied(Authorisation failed)
at com.ddtek.jdbc.openedge.client.ddd.aw(Unknown Source)
at com.ddtek.jdbc.openedge.client.ddd.j(Unknown Source)
at com.ddtek.jdbc.openedge.OpenEdgeImplConnection.j(Unknown Source)
at com.ddtek.jdbc.openedgebase.BaseConnection.b(Unknown Source)
at com.ddtek.jdbc.openedgebase.BaseConnection.k(Unknown Source)
at com.ddtek.jdbc.openedgebase.BaseConnection.b(Unknown Source)
at com.ddtek.jdbc.openedgebase.BaseConnection.a(Unknown Source)
at com.ddtek.jdbc.openedgebase.BaseDriver.connect(Unknown Source)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at com.ncr.sj250216.JdbcTest.main(JdbcTest.java:18)
There is no compile time error in my code, i am using the right jars as referenced libraries.
package com.ncr.sj250216;
import java.sql.*;
public class JdbcTest
{
public static String
URL="jdbc:datadirect:openedge://sun3899.daytonoh.ncr.com:28409;DatabaseName=dispatch";
public static String username="CSMSRUP";
public static String password=null;
public static void main(String [] args)
{
try
{
Class.forName ("com.ddtek.jdbc.openedge.OpenEdgeDriver");
System.out.println("Driver loaded");
Connection conn = DriverManager.getConnection(URL,username,password);
System.out.println("Connected");
Statement stmt = conn.createStatement();
System.out.println("Statement created");
ResultSet rs = stmt.executeQuery("select remark from pub.dupdate_remarks");
System.out.println("ResultSet : \n");
while (rs.next())
{
System.out.println(rs.getString(1));
}
System.out.println("AFTER CRUISING THROUGH THE RESULT SET");
rs.close();
stmt.close();
conn.close();
}
catch (Exception x)
{
x.printStackTrace();
}
}
}
Access denied and Authorization failed mean that you either have the wrong userid & password or you are attempting to connect to the wrong db.
If you have access to the server that the db runs on you can test your credentials using Progress' sqlexp command line tool:
sqlexp -user userName -password passWord -db dnName -S servicePort
Or you could use any popular Windows based SQL querying tool to try the connection...
Die Datenbank 'C:\TEMP\derbyDB01' konnte nicht mit dem Klassenladeprogramm sun.misc.Launcher$AppClassLoader#253498 gestartet werden. Details können Sie der nächsten Ausnahme entnehmen.
at org.apache.derby.impl.jdbc.SQLExceptionFactory40.getSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.newEmbedSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.seeNextException(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.bootDatabase(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.<init>(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection30.<init>(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection40.<init>(Unknown Source)
at org.apache.derby.jdbc.Driver40.getNewEmbedConnection(Unknown Source)
at org.apache.derby.jdbc.InternalDriver.connect(Unknown Source)
at org.apache.derby.jdbc.AutoloadedDriver.connect(Unknown Source)
at java.sql.DriverManager.getConnection(DriverManager.java:579)
at java.sql.DriverManager.getConnection(DriverManager.java:243)
at Importer.getCon(Importer.java:88)
this is the part of the code, causing the exception:
private static final String jdbc_driver = "org.apache.derby.jdbc.EmbeddedDriver";
private static Connection conn = null;
public void importToDB(String DB_URL, String[] header, List<Data> dataList, File csv ) throws SQLException, ClassNotFoundException {
stmt = null;
ResultSet rs = null;
String sql = null;
String tablename = spl.getTableName(csv);
Class.forName(jdbc_driver);
if (conn == null) {
conn = getCon(DB_URL);
}
...
public static Connection getCon(String DB_URL) throws SQLException {
System.out.println("Connecting to a selected database...");
conn = DriverManager.getConnection(DB_URL);
System.out.println("Connected successfully...");
return conn;
}
the String DB_URL is given to the method by taking it from a JTextfield. the URL I use is correct, because the program worked with it, before adding the GUI. it is: "jdbc:derby:C:\TEMP\derbyDB01"
So what is causing so much problems in here?
According to Derby developer guide, you need to reverse the slashes in URL
jdbc:derby:c:/TEMP/derbyDB01
Sorry for taking so long to Update this.
Almost forgot I had it posted here. The problem was that I opened the database connection via an eclipse db plugin. When closing that plugin, it doesn't properly close the connection, which then produces in this exception when the program is trying do gain access again.
I am trying to run a JAVA program which inserts values into mySQL database. When I run the program, it says Connection refused: connect I have included mySQL jars also. What is the problem? Can anyone help me out
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
public class DataLogs {
public static void main(String[] args) throws SQLException,ClassNotFoundException {
Connection connection = null;
try {
//int i=0;
String strDate="", strTime="";
// Register MySQL JDBC driver to be known by
// the DriverManager object.
Class.forName("com.mysql.jdbc.Driver");
// Get a connection to database. We prepare the
// connection information here such as database
// url, user and password.
String url = "jdbc:mysql://localhost:8080/sampledatabase";
String user = "root";
String password = "root";
connection = DriverManager.getConnection(url, user, password);
// Create a statement object instance from the
// connection
Statement stmt = connection.createStatement();
// We are going to execute an insert statement.
// First you have to create a table that has an
// ID, NAME and ADDRESS field. For ID you can use
// an auto number, while NAME and ADDRESS are
// VARCHAR fields.
for(int i=1;i<=100;i++){
Date date = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
String formattedDate = sdf.format(date);
strDate=getFormatedDate();
strTime=getTime();
String mm=strDate.substring(3, 5);
String yy=strDate.substring(8, 10);
String hh=strTime.substring(0, 2);
String mi=strTime.substring(3, 5);
String ss=strTime.substring(6, 8);
String dd=strDate.substring(0, 2);
String date1 = ""+yy+"-"+mm+"-"+dd+" "+hh+":"+mi+":"+ss;
String sql= "INSERT INTO `site_values_"+i+"` VALUES("+i+",5316,0,0,130,89,904,171,1006,96,4000,"+ss+","+mi+","+hh+","+dd+","+mm+","+yy+",84753,0,0,0,0,0,0,0,0,0,'Short Circuit Shutdown','Shutdown',1,'"+date1+"')";
// Call an execute method in the statement object
// and passed the sql or query string to it.
stmt.execute(sql);
}
// After this statement is executed you'll have a
// record in your users table.
} catch (ClassNotFoundException e) {
System.err.println("Could not load database driver!"+e);
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (connection != null) {
connection.close();
}
}
}
public static String getFormatedDate() {
String strDate="";
Calendar cal = Calendar.getInstance();
SimpleDateFormat sdfdate = new SimpleDateFormat("dd/MM/yyyy");
strDate= sdfdate.format(cal.getTime());
return strDate;
}//getFormatedDate
public static String getTime() {
DateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
java.util.Date date = new java.util.Date();
String datetime = dateFormat.format(date);
return datetime;
} //getTime
}
This is what I see in the console
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1116)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2332)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2369)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2153)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at solarnmsstandard.DataLogs.main(DataLogs.java:27)
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at java.net.Socket.<init>(Unknown Source)
at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:257)
at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:294)
... 15 more
Check if your connection parameters are correct (username, password) and especially the port where the MySql server is running.
check whether your mysql server is running or not, if it is not running then you will get this exception
java.net.ConnectException: Connection refused: connect
to run server
go to <mysql installation path>/bin/ and run mysqld.. to start the mysql server.
even after if you get the same error, provide the full stack trace.
check your port 8080 is free or not
if you are use linux run the follwing command and restart your server.
sudo kill sudo lsof -t -i:8080
sudo kill sudo lsof -t -i:8005
sudo kill sudo lsof -t -i:8009
I would be very suspicious of port 8080 being used as the port for MySQL; it really should be port 3306. So that would have to be checked properly as 8080 is usually the port number for an Application Server instance (such as GlassFish or Tomcat).
I've installed MaxDB in my local machine and I'm trying to make a connection to it using Java.
And I'm getting this error when running :
Exception in thread "main"
java.lang.ClassNotFoundException:
com.sap.dbtech.jdbc.DriverSapDB
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at sap.maxdb.Hello.main(Hello.java:15)
This is the code I'm using :
package sap.maxdb;
import java.sql.*;
public class Hello
{
public static void main(String[] args) throws ClassNotFoundException, SQLException
{
String username = "DBM";
String password = "azerty";
String dbname = "SAPDB";
Class.forName ("com.sap.dbtech.jdbc.DriverSapDB");
String url = "jdbc:sapdb://" + dbname;
Connection connection = DriverManager.getConnection (url, username, password);
Statement stmt = connection.createStatement ();
ResultSet resultSet = stmt.executeQuery ("SELECT * FROM HOTEL.CUSTOMER");
resultSet.next ();
String hello = resultSet.getString (1);
System.out.println (hello);
resultSet.close ();
stmt.close();
connection.close ();
}
}
I did like they said in their website :
set CLASSPATH=%CLASSPATH%;C:\Program
Files\sdb\programs\runtime\jar\sapdbc.jar
But I get always the same error.
I know that I'm missing something but can't find it °!°
Waiting for your help.
Thanks.
What does "install" mean? Basically, the db server must be installed and running.
Step two is to add the driver (which you can find under C:\Program Files\sdb\programs\runtime\jar\sapdbc.jar, assuming this applies to your installation too) to the build path of your project. If the driver class cannot be found, it'll raise a ClassNotFoundException as you experienced.
You don't mention which IDE you are using, but try to set your project buildpath from the context menu.
Try adding the following code to make sure that your application picks up the CLASSPATH that you specified:
Map<String, String> env = System.getenv();
for (String envName : env.keySet()) {
System.out.format("%s=%s%n", envName, env.get(envName));
}
Copy the driver's jar file to the 'lib' folder of the server. Then restart the server.