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).
Related
I can't work out why the following program is unable to locate tables in my derby database:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Properties;
import java.util.logging.Level;
import java.util.logging.Logger;
public class NdConnect
{
public final static String SETUP_FILE_PATH = "/AppData/Local/NewdawnTest";
private static final String CONNECTION_URL = "jdbc:derby:" + "C:/Users/" + System.getenv("USERNAME") + SETUP_FILE_PATH + "db" + ";create=true";
private static Connection conn = null;
private final static Properties dbProperties = new Properties();
private static PreparedStatement pstmtSelectTxns;
public static void connect() {
try {
conn = DriverManager.getConnection(CONNECTION_URL + ";create=true", dbProperties);
pstmtSelectTxns = conn.prepareStatement("SELECT * from TXNS");
System.out.println("Connected OK to " + CONNECTION_URL);
}
catch (SQLException sqle) {
System.out.println("SQL exception");
System.out.println("Connected NOK:The connection URL is " + CONNECTION_URL);
Logger.getLogger(NdConnect.class.getName()).log(Level.SEVERE, null, sqle);
}
}
public static void disconnect()
{
try {
if (conn != null) {
conn.close();
conn = null;
System.out.println("0048 NDC OK:DB closed ");
}
} catch (SQLException sqle) {
Logger.getLogger(NdConnect.class.getName()).log(Level.SEVERE, null, sqle);
}
}
public static void main(String[] args)
{
// NdConnect nd = new NdConnect();
NdConnect.connect();
NdConnect.disconnect();
// System.out.println("NdConnect finished");
}
}
The program throws a SQLSyntaxErrorException:
run:
SQL exception
Connected NOK:The connection URL is jdbc:derby:C:/Users/Administrator/AppData/Local/NewdawnTestdb;create=true
Nov 25, 2018 6:58:42 AM NdConnect connect
0048 NDC OK:DB closed
SEVERE: null
java.sql.SQLSyntaxErrorException: Table/View 'TXNS' does not exist.
at org.apache.derby.impl.jdbc.SQLExceptionFactory.getSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.Util.generateCsSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(Unknown Source)
at org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.handleException(Unknown Source)
at org.apache.derby.impl.jdbc.ConnectionChild.handleException(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedPreparedStatement.<init>(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedPreparedStatement42.<init>(Unknown Source)
at org.apache.derby.jdbc.Driver42.newEmbedPreparedStatement(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown Source)
at org.apache.derby.impl.jdbc.EmbedConnection.prepareStatement(Unknown Source)
at NdConnect.connect(NdConnect.java:21)
at NdConnect.main(NdConnect.java:47)
Caused by: ERROR 42X05: Table/View 'TXNS' does not exist.
at org.apache.derby.iapi.error.StandardException.newException(Unknown Source)
at org.apache.derby.iapi.error.StandardException.newException(Unknown Source)
at org.apache.derby.impl.sql.compile.FromBaseTable.bindTableDescriptor(Unknown Source)
at org.apache.derby.impl.sql.compile.FromBaseTable.bindNonVTITables(Unknown Source)
at org.apache.derby.impl.sql.compile.FromList.bindTables(Unknown Source)
at org.apache.derby.impl.sql.compile.SelectNode.bindNonVTITables(Unknown Source)
at org.apache.derby.impl.sql.compile.DMLStatementNode.bindTables(Unknown Source)
at org.apache.derby.impl.sql.compile.DMLStatementNode.bind(Unknown Source)
at org.apache.derby.impl.sql.compile.CursorNode.bindStatement(Unknown Source)
at org.apache.derby.impl.sql.GenericStatement.prepMinion(Unknown Source)
at org.apache.derby.impl.sql.GenericStatement.prepare(Unknown Source)
at org.apache.derby.impl.sql.conn.GenericLanguageConnectionContext.prepareInternalStatement(Unknown Source)
... 7 more
However the database and table do exist. I have verified this by creating a connection to the database in Netbeans > Services. When I run this command in Services:
SELECT * from TXNS
the desired table is correctly displayed and the output window returns:
Executed successfully in 0 s.
Fetching resultset took 0.016 s.
Line 1, column 1
Execution finished after 0.254 s, no errors occurred.
Looking at the properties of this connection via Netbeans services shows the following attribute values:
Display name NewDawn – TEST DB
Database URL jdbc:derby:C:\Users\Administrator\AppData\Local\NewdawnTest\db
Driver apache_derby_embedded
Driver class org.apache.derby.jdbc.EmbeddedDriver
This seems to correspond to the setup I have in the java code example so I don't understand why the code doesn't work.
The URL is not the same:
In Netbeans: jdbc:derby:C:\Users\Administrator\AppData\Local\NewdawnTest\db
In Java: jdbc:derby:C:/Users/Administrator/AppData/Local/NewdawnTestdb;create=true
Change the CONNECTION_URL line to:
private static final String CONNECTION_URL = "jdbc:derby:" + "C:/Users/" + System.getenv("USERNAME") + SETUP_FILE_PATH + "/db"
I am building a swing application to download multiple files over the internet and save to a windows fileshare. I have used SwingWroker which internally uses the ExecutorService which internally queues them and downloads 10 at a time, but for some reason after downloading say 2 - 3 MB of file it stops and moves to next downloading file, They are downloaded in a batch of 10 as SwingWorker has fixed it in number of Threads for the Executor Service.
I have to write these files in a windows file share and I am using nio.FileChannels to do that. There are files ranging from 50-60 each weighing around 300MB - 500MB. The file links are located on a webpage to where I get to by login in using credentials on a login page(with a post request) over the internet before that I specify CookieHandler.setDefault(new CookieManager()) at the beginning and so it behaves like a browser to me.
Another observation is when I download them locally (not to a windows server share) they do work fine.
This is the code I am using
import java.io.File;
import java.io.FileOutputStream;
import java.net.URL;
import java.net.URLConnection;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.ReadableByteChannel;
import javax.swing.SwingWorker;
public class DownloadProcess extends SwingWorker<Boolean, String> {
private String urlPath, filePath;
public DownloadProcess(String urlPath, String filePath){
this.urlPath = urlPath;
this.filePath = filePath;
}
#Override
protected Boolean doInBackground() {
boolean taskState = true;
URLConnection httpConn = null;
ReadableByteChannel readableByteChannel = null;
FileOutputStream fileOutputStream = null;
FileChannel fileOutputChannel = null;
try{
//String filePath = "\\\\fileshare.server\\xyz.txt";
//String urlPath = "http://example.com/anyBigFile.1GB.docx";
File localFile = new File(filePath);//File share
boolean itsThere = localFile!=null && localFile.exists();
long done = itsThere ? localFile.length() : 0;
URL url = new URL(urlPath);
httpConn = url.openConnection();
httpConn.setRequestProperty("Connection", "keep-alive");
if(itsThere) {
httpConn.setRequestProperty("Range","bytes="+done+"-");
}
readableByteChannel = Channels.newChannel(httpConn.getInputStream());
fileOutputStream = itsThere ? new FileOutputStream(filePath) : new FileOutputStream(filePath,true);
fileOutputChannel = fileOutputStream.getChannel();
for (long position = done, size = httpConn.getContentLength(); position < size && !isCancelled(); ) {
position += fileOutputChannel.transferFrom(readableByteChannel, position, 1 << 16);
}
//done
}catch(Exception e){
taskState = false;
e.printStackTrace();
}finally{
//close streams conns etc
}
return taskState;
}
}
This is the error stack trace that I get after 5 - 10 mins of download
/*
javax.net.ssl.SSLException: Connection has been shutdown: javax.net.ssl.SSLException: java.net.SocketException: Connection reset
at sun.security.ssl.SSLSocketImpl.checkEOF(Unknown Source)
at sun.security.ssl.AppInputStream.read(Unknown Source)
at java.io.BufferedInputStream.read1(Unknown Source)
at java.io.BufferedInputStream.read(Unknown Source)
at sun.net.www.MeteredStream.read(Unknown Source)
at java.io.FilterInputStream.read(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection$HttpInputStream.read(Unknown Source)
at java.nio.channels.Channels$ReadableByteChannelImpl.read(Unknown Source)
at com.objects.DownloadByteChannel.read(DownloadByteChannel.java:117)
at sun.nio.ch.FileChannelImpl.transferFromArbitraryChannel(Unknown Source)
at sun.nio.ch.FileChannelImpl.transferFrom(Unknown Source)
at com.core.DownloadTask.doInBackground(DownloadTask.java:154)
at com.core.DownloadTask.doInBackground(DownloadTask.java:59)
at com.util.ZSwingWorker$1.call(ZSwingWorker.java:286)
at java.util.concurrent.FutureTask.run(Unknown Source)
at com.util.ZSwingWorker.run(ZSwingWorker.java:325)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: javax.net.ssl.SSLException: java.net.SocketException: Connection reset
at sun.security.ssl.Alerts.getSSLException(Unknown Source)
at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
at sun.security.ssl.SSLSocketImpl.handleException(Unknown Source)
at sun.security.ssl.SSLSocketImpl.handleException(Unknown Source)
... 18 more
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at java.net.SocketInputStream.read(Unknown Source)
at sun.security.ssl.InputRecord.readFully(Unknown Source)
at sun.security.ssl.InputRecord.read(Unknown Source)
at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
at sun.security.ssl.SSLSocketImpl.readDataRecord(Unknown Source)
... 18 more
*/
Usage:
public static void main(String[] args){
int counter = 1;
for(String url: urls){
new DownloadProcess(url,"\\\\fileshare.server\\xyz"+(counter++)+".txt").execute();
}
}
You are going to have to change your connection timeout serverside. I picked up a few links along the way if they are of any importance:
Modify Session Security settings
Lengthening salesforce session timeout
Hope this helps, good luck and let me know :)
Connection Reset means the remote side is closing the connection with a TCP RST (reset) packet. You need to find out what the remote side isn't liking and fix it.
If the remote side is Apache maybe you are running into the KeepAliveTimeout value. By default that is 5 seconds. It really sounds like you are running into some sort of configured limit on the remote side. When that happens the server is kicking you off with a reset.
I am trying to connect to a gmail inbox to listen to messages using the JavaMail api. I can connect fine to the mailbox when I run my program through the main method. However when I create a separate thread and run it using some other class it seems that I get the following exception.
javax.mail.MessagingException: null; nested exception is:
java.io.IOException
at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:298)
at javax.mail.Service.connect(Service.java:234)
at javax.mail.Service.connect(Service.java:135)
at com.emdi.sl3.server.emailConnector.EmailListenerAcknowledge.run(Email ListenerAcknowledge.java:92)
at java.lang.Thread.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)`
My code to connect to the mailbox looks like,
import java.util.*;
import javax.mail.*;
import javax.mail.event.*;
import com.sun.mail.imap.*;
public class EmailListenerAcknowledge implements Runnable {
private Store store;
private Folder folder;
String host;
String user;
String password;
public void run() {
try {
// TODO: Set email protocol, username and password.
host = "imap.gmail.com";
user = "fdsfds";
password = "sdfsff";
String mbox = "inbox";
String frequency = "1";
System.out.println("\nTesting monitor\n");
Properties props = new Properties();
props.setProperty("mail.imap.ssl.enable", "true");
props.setProperty("mail.imap.port", "993");
// Get a Session object
Session session = Session.getInstance(props);
// Get a Store object
store = session.getStore("imap");
// Connect
store.connect(host, user, password);
System.out.println("Connected!!!");
// Open a Folder
folder = store.getFolder(mbox);
if (folder == null || !folder.exists()) {
System.out.println("Invalid folder");
System.exit(1);
}
folder.open(Folder.READ_ONLY);
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
I also notice that when I remove the line props.setProperty("mail.imap.port", "993"), I get a different exception (again running the program from the main method works fine),
javax.mail.MessagingException: Connection timed out: connect; nested exception is:java.net.ConnectException: Connection timed out: connect
at com.sun.mail.imap.IMAPStore.protocolConnect(IMAPStore.java:298)
at javax.mail.Service.connect(Service.java:234)
at javax.mail.Service.connect(Service.java:135)
at com.emdi.sl3.server.emailConnector.EmailListener.run(Email ListenerAcknowledge.java:92)
at java.lang.Thread.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)`
I seem not to understand why running the program from the main method works fine whereas running the program from a separate thread don't work.
I am attempting to connect to an Oracle database through Java with the Oracle JDBC driver with the following code (obscuring the host, service, user, and password):
import java.sql.*;
public class Main {
public Main () {
try {
String host = "HOST_NAME";
String port = "1521";
String service = "SERVICE_NAME";
String user = "SCHEMA_USER";
String password = "SCHEMA_PASSWORD";
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection = DriverManager.getConnection("jdbc:oracle:thin:#(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=" +
host +
")(PORT=" +
port +
")))(CONNECT_DATA=(SERVICE_NAME=" +
service +
")))",
user,
password);
connection.close ();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main (String args) {
new Main ();
}
}
However, I receive the following error:
java.sql.SQLException: IO Error: The Network Adapter could not establish the connection
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:458)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:546)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:236)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521)
at java.sql.DriverManager.getConnection(Unknown Source)
at java.sql.DriverManager.getConnection(Unknown Source)
at com.acxiom.axle.reporting.database.DatabaseConnection.connect(DatabaseConnection.java:23)
at com.acxiom.axle.reporting.Reporting.establishDatabaseConnection(Reporting.java:53)
at com.acxiom.axle.reporting.Reporting.beginReporting(Reporting.java:20)
at com.acxiom.axle.reporting.Entry.<init>(Entry.java:28)
at com.acxiom.axle.reporting.Entry.main(Entry.java:118)
Caused by: oracle.net.ns.NetException: The Network Adapter could not establish the connection
at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:392)
at oracle.net.resolver.AddrResolution.resolveAndExecute(AddrResolution.java:434)
at oracle.net.ns.NSProtocol.establishConnection(NSProtocol.java:687)
at oracle.net.ns.NSProtocol.connect(NSProtocol.java:247)
at oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:1102)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:320)
... 11 more
Caused by: java.net.UnknownHostException: null
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(Unknown Source)
at java.net.InetAddress.getAddressesFromNameService(Unknown Source)
at java.net.InetAddress.getAllByName0(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at java.net.InetAddress.getAllByName(Unknown Source)
at oracle.net.nt.TcpNTAdapter.connect(TcpNTAdapter.java:117)
at oracle.net.nt.ConnOption.connect(ConnOption.java:133)
at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:370)
... 16 more
The strange thing is, I can connect to the database from PL/SQL Developer, I can ping the remote host, and I can telnet to the remote host on port 1521.
Why would only Java appear to give an UnknownHostException, but I can connect and ping the host with other applications?
EDIT: I removed "hr/hr" from the connection string above. I have tried the connection as-is with it removed and still receive the same error. I've also tried changing the connection string to match the version morgano listed in his answer, with the same result. Finally, I tried to change the port number to a port I know it's not listening on, and it still receives the same error.
The connection string is of the correct format. The problem is that the host isn't set. It's null, or perhaps the string "null". There's simply no other way to generate the error message java.net.UnknownHostException: null
In your sample code, you write String host = "HOST_NAME";. This makes it look like in your real code you are assigning a constant string to the variable host. However, I'm going to stick my neck out and say that in your real code you are not doing this. You are looking up the host name from somewhere, this lookup fails for some reason, you don't check this, and hence you pass a null value into the connection string.
Your JDBC url is wrong, according to the documentation it should be something like:
jdbc:oracle:driver_type:[username/password]#//host_name:port_number/service_name
In your case your code would be something like:
import java.sql.*;
public class Main {
public Main () {
try {
String host = "HOST_NAME";
String port = "1521";
String service = "SERVICE_NAME";
String user = "SCHEMA_USER";
String password = "SCHEMA_PASSWORD";
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection = DriverManager.getConnection(
"jdbc:oracle:thin:#//" + host
+ ":" + port + "/" + service, user, password);
connection.close ();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main (String args) {
new Main ();
}
}
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.