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PGJDBC: could not receive data from client:

Dear StackOverFlowers,
I was trying event-driven LISTENER/NOTIFY on Postgres 9.6 (Windows 10).
I followed PGJDBC example given by Steve Taylor at https://www.openmakesoftware.com/postgresql-listen-notify-events-example/.
I started by downloading pgjdbc-ng-0.7-complete.jar and have put that in my CLASSPATH replacing standard JDBC driver.
When I am trying to connect to Postgres database using pgjdbc driver, I am getting an error:
connection received: host=127.0.0.1 port=50325
connection authorized: user=postgres database=scott
could not receive data from client: An existing connection was forcibly closed by the remote host.
Here are my system variables:
DBHost: localhost
DBName: scott
DBPort: 5432
DBUserName: postgres
DBPassword: postgres
I am not getting past the first hurdle, rest looks like Mount Everest. Please help me. Should you be needing the code, I am following Steve's code ditto.
Further to Joseph Larson's answer, the database is always running. I have connected to Postgres database from PGADMIN and Java successfully. I think issue is with the connect string. From Java when I am using standard JDBC which is provided by Postgres I am using URL like jdbc:postgresql://localhost:5432/dbname but PGJDBC suggests a different connect string like JDBC:PGSQL://localhost:5432/dbname. I tried to connect with that string (forcibly), it did not work. There is no method in PGJDBC PGDataSource for providing URL directly. I had to go through:
dataSource.setHost(DBHost);
dataSource.setPort(5432);
dataSource.setDatabase(DBName);
dataSource.setUser(DBUserName);
dataSource.setPassword(DBPassword);
And what URL it is sending to Database I am not able to figure out. Please suggest me a connect string and this problem is solved.
thanks
Thanks very much for asking me to post error messages:
Exception in thread "main" java.lang.NullPointerException
at com.impossibl.postgres.system.BasicContext.loadLocale(BasicContext.java:294)
at com.impossibl.postgres.system.BasicContext.init(BasicContext.java:273)
at com.impossibl.postgres.jdbc.PGConnectionImpl.init(PGConnectionImpl.java:251)
at com.impossibl.postgres.jdbc.ConnectionUtil.createConnection(ConnectionUtil.java:182)
at com.impossibl.postgres.jdbc.AbstractDataSource.createConnection(AbstractDataSource.java:723)
at com.impossibl.postgres.jdbc.PGDataSource.getConnection(PGDataSource.java:66)
at com.impossibl.postgres.jdbc.PGDataSource.getConnection(PGDataSource.java:58)
at PGListenNotify.<init>(PGListenNotify.java:26)
at PGListenNotify.main(PGListenNotify.java:37)
Here is source code:
import java.sql.SQLException;
import java.sql.Statement;
import com.impossibl.postgres.api.jdbc.PGConnection;
import com.impossibl.postgres.jdbc.PGDataSource;
public class PGListenNotify
{
PGConnection connection;
public PGListenNotify()
{
String DBHost = System.getenv("DBHost");
String DBName = System.getenv("DBName");
String DBUserName = System.getenv("DBUserName");
String DBPassword = System.getenv("DBPassword");
try
{
PGDataSource dataSource = new PGDataSource();
dataSource.setHost(DBHost);
dataSource.setPort(5432);
dataSource.setDatabase(DBName);
dataSource.setUser(DBUserName);
dataSource.setPassword(DBPassword);
connection = (PGConnection) dataSource.getConnection();
Statement statement = connection.createStatement();
}
catch (SQLException e)
{
e.printStackTrace();
}
}
public static void main(String[] args)
{
PGListenNotify ln = new PGListenNotify();
}
}

This looks like the Windows locale bug in pgjbdc-ng. It has been addressed, try the latest version 0.8.1.
The latest releases have detailed documentation related to asynchronous notifications here.
If it still fails to execute on your Windows system, please create an issue here.

Did you actually start a database server? I didn't know PostgreSQL server could run on Windows, but I've never tried.
I would simplify your problem a little. I know nothing about psql on Windows, but on Mac, I would start the server and then use the psql command (it's part of PostgreSQL) to ensure the server was up and running.
If you're to connecting, then the problems can be:
-There is no server at all
-The server isn't running on the port you're attempting
-The server isn't listening for connections on host 127.0.0.1 but could be listening on the actual IP address of your machine
-I'm not sure about that particular error, but username, password, or database may not exist.
I'd use psql to figure out which of those possible reasons is the real problem. That isolates out your program as being part of the problem, and it becomes entirely one of managing your database server.

Hive JDBC connection problems

I am trying to connect to Hive2 server via JDBC with kerberos authentication. After numerous attempts to make it work, I can't get it to work with the Cloudera driver.
If someone can help me to solve the problem, I can greatly appreciate it.
I have this method:
private Connection establishConnection() {
final String driverPropertyClassName = "driver";
final String urlProperty = "url";
Properties hiveProperties = config.getMatchingProperties("hive.jdbc");
String driverClassName = (String) hiveProperties.remove(driverPropertyClassName);
String url = (String) hiveProperties.remove(urlProperty);
Configuration hadoopConfig = new Configuration();
hadoopConfig.set("hadoop.security.authentication", "Kerberos");
String p = config.getProperty("hadoop.core.site.path");
Path path = new Path(p);
hadoopConfig.addResource(path);
UserGroupInformation.setConfiguration(hadoopConfig);
Connection conn = null;
if (driverClassName != null) {
try {
UserGroupInformation.loginUserFromKeytab(config.getProperty("login.user"), config.getProperty("keytab.file"));
Driver driver = (Driver) Class.forName(driverClassName).newInstance();
DriverManager.registerDriver(driver);
conn = DriverManager.getConnection(url, hiveProperties);
} catch (Throwable e) {
LOG.error("Failed to establish Hive connection", e);
}
}
return conn;
}
URL for the server, that I am getting from the properties in the format described in Cloudera documentation
I am getting an exception:
2018-05-05 18:26:49 ERROR HiveReader:147 - Failed to establish Hive connection
java.sql.SQLException: [Cloudera][HiveJDBCDriver](500164) Error initialized or created transport for authentication: Peer indicated failure: Unsupported mechanism type PLAIN.
at com.cloudera.hiveserver2.hivecommon.api.HiveServer2ClientFactory.createTransport(Unknown Source)
at com.cloudera.hiveserver2.hivecommon.api.ZooKeeperEnabledExtendedHS2Factory.createClient(Unknown Source)
...
I thought, that it is missing AuthMech attribute and added AuthMech=1 to the URL. Now I am getting:
java.sql.SQLNonTransientConnectionException: [Cloudera][JDBC](10100) Connection Refused: [Cloudera][JDBC](11640) Required Connection Key(s): KrbHostFQDN, KrbServiceName; [Cloudera][JDBC](11480) Optional Connection Key(s): AsyncExecPollInterval, AutomaticColumnRename, CatalogSchemaSwitch, DecimalColumnScale, DefaultStringColumnLength, DelegationToken, DelegationUID, krbAuthType, KrbRealm, PreparedMetaLimitZero, RowsFetchedPerBlock, SocketTimeOut, ssl, StripCatalogName, transportMode, UseCustomTypeCoercionMap, UseNativeQuery, zk
at com.cloudera.hiveserver2.exceptions.ExceptionConverter.toSQLException(Unknown Source)
at com.cloudera.hiveserver2.jdbc.common.BaseConnectionFactory.checkResponseMap(Unknown Source)
...
But KrbHostFQDN is already specified in the principal property as required in the documentation.
Am I missing something or is this documentation wrong?

Below is the one of the similar kind of problem statement in Impala (just JDBC engine changes others are same) that is resolved by setting "KrbHostFQDN" related properties in JDBC connection string itself.
Try to use the URL below. Hopefully works for u.
String jdbcConnStr = "jdbc:impala://myserver.mycompany.corp:21050/default;SSL=1;AuthMech=1;KrbHostFQDN=myserver.mycompany.corp;KrbRealm=MYCOMPANY.CORP;KrbServiceName=impala"
I suppose that if you are not using SSL=1 but only Kerberos, you just drop that part from the connection string and don't worry about setting up SSL certificates in the java key store, which is yet another hassle.
However in order to get Kerberos to work properly we did the following:
Install MIT Kerberos 4.0.1, which is a kerberos ticket manager. (This is for Windows)
This ticket manager asks you for authentication every time you initiate a connection, creates a ticket and stores it in a kerberos_ticket.dat binary file, whose location can be configured somehow but I do not recall exactly how.
Finally, before launching your JAVA app you have to set an environment variable KRB5CCNAME=C:/path/to/kerberos_ticket.dat. In your java app, you can check that the variable was correctly set by doing System.out.println( "KRB5CCNAME = " + System.getenv( "KRB5CCNAME" ) ). If you are working with eclipse or other IDE you might even have to close the IDE,set up the environment variable and start the IDE again.
NOTE: this last bit is very important, I have observed that if this variable is not properly set up, the connection wont be established...
In Linux, instead MIT Kerberos 4.0.1, there is a program called kinit which does the same thing, although without a graphical interface, which is even more convenient for automation.

I wanted to put it in the comment but it was too long for the comment, therefore I am placing it here:
I tried your suggestion and got another exception:
java.sql.SQLException: [Cloudera]HiveJDBCDriver Error
creating login context using ticket cache: Unable to obtain Principal
Name for authentication .
May be my problem is, that I do not have environment variable KRB5CCNAME set.
I, honestly, never heard about it before.
What is supposed to be in that ticket file.
I do have, however, following line in my main method:
System.setProperty("java.security.krb5.conf", "path/to/krb5.conf");
Which is supposed to be used by
UserGroupInformation.loginUserFromKeytab(config.getProperty("login.user"), config.getProperty("keytab.file"));
to obtain the kerberos ticket.

To solve this issue update Java Cryptography Extension for the Java version that you use in your system.
Here's the link when you can download JCE for Java 1.7
Uncompress and overwrite those files in $JDK_HOME/jre/lib/security
Restart your computer.

Connection to derby database refused

I am learning Java and trying to put together a simple App containing a few jTables connected to database that can be updated etc. To do this I have created a database with a few tables through Netbeans which I understand (and wish) to be embedded in the final distributable app.
I am following the Programming Knowledge tutorials on Youtube to create most of the GUI. Everting is OK as long as I open the Services tab on Netbeans and manually right-click my database(testDB) and click Start Server. Then when I run the following code I get a successful connection:
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
try{
//Register JDBC driver
Class.forName("org.apache.derby.jdbc.ClientDriver");
//Open a connection
String DB_URL = "jdbc:derby://localhost:1527/testDB";
String u_name = jTextField1.getText();
String p_word = jPasswordField1.getText();
conn = DriverManager.getConnection("jdbc:derby://localhost:1527/testDB",u_name,p_word);
JOptionPane.showMessageDialog(null,"Details Correct - Connection established");
Close_me();
Open_Table_GUI(u_name,p_word);
}
catch(ClassNotFoundException | SQLException e){
System.out.println(e);
}
}
However if I run that code WITHOUT manually clicking on start server I get the following:
java.sql.SQLNonTransientConnectionException: java.net.ConnectException : Error connecting to server localhost on port 1,527 with message Connection refused.
I have read the apache documentation and due to my level of inexperience I am not getting anywhere.
I have also checked out the answers to similar connection questions on here but again I can't seem to relate the issue in a way that works.
The ultimate goal for me is to have an app I can distribute to run on windows machines that will have the database/tables all included individually editable etc. I would hope to eventually create a database that resides on a shared drive and each individual can connect to automatically - but that's way down the line for now.
My request here is that someone can help me understand what I need to change in my code so that the "Start Server" is automatically done.
Thanks in advance for nay response.

OK guys so I found code that seems to work for me from a question asked on here by LMS
private void setup(){
try{
Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
connection=DriverManager.getConnection("jdbc:derby:sheet;create=true","test","1234");
statement=connection.createStatement();
}
catch(ClassNotFoundException cnf){
System.out.println("class error");
}
catch(SQLException se){
System.out.println(se);
}
}
If anyone cares to link me to a reason why this in fact works that would be great, I'm assuming the Embedded driver doesn't go through the port and just looks within the project??
Anyway initially this seems to be solved!!

Please check your Server setting i.e.
-username and pwd in your program
and check that did you start the Derby server and is it listening at port 1527?

MySQL denied access in java, workbench access granted

I've been using java on a computer (lets call it PC1) to connect to a database on a server, and until recently it was working with no errors.
By working, I mean I could connect to the server using java on PC1, and access the info I needed from the tables using select statements.
The only changes that have been made are the ip addresses on PC1 and the server.
After changing the IP addresses, I then updated the grant table in mysql, and yet, I get the following error:
java.sql.SQLException: Access denied for user 'robot'#'aa-PC' (using password: YES)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:946)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2985)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:885)
at com.mysql.jdbc.MysqlIO.secureAuth411(MysqlIO.java:3421)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1247)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:2775)
at com.mysql.jdbc.Connection.<init>(Connection.java:1555)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:285)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at WriteToMySql.connection1(WriteToMySql.java:26)
at WriteToMySql.main(WriteToMySql.java:259)
The strange part however, is that I am able to connect to the server's database using the mySQL workbench and access all data on them.
here's the java code:
String host = "jdbc:mysql://PC1IPAdress:3306/users";
String user= "robot";
String password="mypassword";
public void connect()
{
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("worked"); //this gets printed
connect = DriverManager.getConnection(host, user, password);
System.out.println("works"); // this does not get printed due to error
stmt = connect.createStatement();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
note: "users" is the name of the database
Any help will be greatly appreciated.
Thank you.
EDIT:
for testing purposes I tried turning off the firewall, but it did not help.

I think there may be an error in the code sample - it connects to PC1IPAddress when you mention that PC1 should be connecting to a server earlier in the post. Just want to make sure before we continue that it was a typo, as otherwise PC1 would be connecting to itself.
If you have administrative access to the server, connect to MySQL as root and use this query to show configured users and ensure the host field is correct: SELECT user, host FROM mysql.user WHERE user='robot';
If the above checks out, I would suggest looking into Windows user authentication. The fact that MySQL returned the Windows computer name ('aa-PC') and not its IP address seems to indicate it may be attempting to authenticate using Windows domain credentials: http://dev.mysql.com/doc/refman/5.5/en/windows-authentication-plugin.html

If you change the ip address of the client (PC1) make sure that you updated the host field as well when granting new rights to user "robot". Check the table "db", "user" and "host".

Java JDBC cannot connect to MSSQL Server

I tried many ways to solve my issue, none of them worked, so here i am with the question. I created a local database with SQL Server Management Studio. It's name is CallCenter, i created a user account for it, granted every privileges and i can log into the DB with it, in the Managemenet Studio, everything works just fine here.
Now i use NetBeans, to create the connection. I downloaded the Microsoft JDBC driver, set up everything, the JDBC seems to be working fine. The problem is, it cannot connect to the Database. I set the log in options to both Windows & SQL. I tried to log in, with integrated sequrity ( windows account ) aswell as the created ( and working ) SQL user account.
None of them worked, i keep getting this exception:
com.microsoft.sqlserver.jdbc.SQLServerException: Login failed for user
'admin'. ClientConnectionId:1ce0b951-5ecb-49b4-a4d0-ff4a96af4ed2 at
com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDatabaseError(SQLServerException.java:216)......
Here is the code:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class Try {
public static void main(String[] args) {
try {
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
String url="jdbc:sqlserver://localhost:1434;databaseName=CallCenter;integratedSecurity=true;";
Connection conn = DriverManager.getConnection(url);
} catch (ClassNotFoundException e) {
System.err.println("SQL Driver class does not exist!");
} catch (SQLException ex) {
ex.printStackTrace();
}
}
}
I've been browsing the internet for hours, tried many solutions, but none of solved this problem for me. Please help me out here!

The Exception pretty much says it all - check your credentials (which you obviously have not given) with the database.

The Login failed for user 'admin' error which you get is a clear indication
that your login request reaches the SQL server but your credentials are wrong.
So either your username or your password is wrong, or maybe this login is not
configured for remote logins to the SQL server. Check your configuration on the server.

Use the other method of the DriverManager to get the connection using the Credentials.
When you have integratedSecurity=True, read this to get more idea on what it actually mean. It uses your windows credentials for login(With SQL Server).
So, make that false and provide credentials for the DB.
For your reference read this
[EDIT]
Try using this instead of integratedSecurity.
jdbc:sqlserver://HOSP_SQL1.company.com;user=name;password=abcdefg;database=Test