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Unable to connect to Oracle database using the JAR file

I'm using eclipse 2020 edition and I've added all libraries I need to connect to Oracle server like ojdbc7.jar and my code is like this:
public Connection SetDatabaseConnection() {
writeInLog("Connecting to IRB", 0);
if(openConnection()){
try {
productionPool.setDriverType("thin");
productionPool.setUser(username);
productionPool.setPassword(password);
productionPool.setPortNumber(Integer.parseInt(port));
productionPool.setServerName(IP);
productionPool.setServiceName(serviceName);
productionPool.setURL("jdbc:oracle:thin:#"+ _connStr.substring(_connStr.indexOf(":")+1));
productionPooledConnection = productionPool.getPooledConnection();
if (productionPooledConnection != null) {
//return true;
currentConnection = productionPooledConnection.getConnection();
logger.info("Connected to IRB server");
return currentConnection;
}
} catch (SQLException ex) {
logger.info("Unable to connect to IRB server, SQLException: "+ex.getMessage());
System.out.println(" (IRB-Exception) DB Exception: \n"+ ex);
}
}
}
my problem is: i can connect to the server while debugging or running the application in the eclipse but when I exported a JAR file the application stopped in this step.
in addition:
my code to open a connection:
private boolean openConnection(){
try {
productionPool = new OracleConnectionPoolDataSource();
productionPooledConnection = new OraclePooledConnection();
logger.info("openConnection(): Connected to IRB server \n");
return true;
} catch (SQLException e) {
e.printStackTrace();
logger.info("Unable to connect to IRB server , SQLException: "+e.getMessage());
}
logger.info("openConnection(): Unable to connect to IRB server \n");
return false;
}
The application never throws any excption it only write in the log file this statment: writeInLog("Connecting to IRB", 0);

I couldn't find the exact reason why this happened but I removed the JARs that cause the error FAT Jar Export: couldn't find the class-path for ...etc and import them again. It worked successfully.

Java Socket connect gives success when connecting to an unknown IP address... why?

I would like to connect by TCP to a machine given its IP address and its port.
I decided to use the JAVA java.net.Socket class and its connect method as it seems to fit my need.
For testing purpose, as the machines I need to test are not yet available, I tried to connect a local machine on its standard port 80.
But I was very surprised to see that it succeeded with any IP address, even an unknown one: I cannot "ping" it, but the connect method gives me success...
Did I missed something in JAVA Socket understanding?
How is this behaviour possible?
Here is my code :
private void testSocketConnection() {
try (Socket socketToMachine = new Socket()) {
InetSocketAddress address = new InetSocketAddress(InetAddress.getByName("1.2.3.4"), 80);
socketToMachine.connect(address, 1000);
System.out.println("SUCCESS");
} catch (UnknownHostException uhe) {
System.out.println("UnknownHostException");
} catch (IOException ioe) {
System.out.println("IOException");
}
}

Slow connection after connection to database with web-hosting

Heading ##I have problem with my java application with database in mySQL and swing GUI.
When I've used localhost everything worked properly. But now I would like to share project with my friend and we decided to use server hosting.
And here is a problem:
Now application works very slow, after pressing a button I have to wait a few seconds for the program to respond. Also the connection is lost from time to time. I have no idea where can I find reason for the problem... Do somebody now what is the reason of this problem?
private static Connection connection = null;
Boolean error = false;
private static String jdbcURL = "jdbc:mysql://host_name:3306/db_name";
private static String user = "user";
private static String password = "password";
MakeConnection(Connection connection) throws SQLException{
this.connection = connection;
try {
getConnection();
System.out.print("Connected to the data base in MakeConnection");
}
catch(Exception e) {
error = true;
System.out.print("Error in connection in MakeConnection consturctor" + e.getMessage());
}
finally{
if(connection!=null) connection.close();
if(error) System.out.print("Problem with connection");
else System.out.print("Program finished");
}
}
public Connection getConnection() throws SQLException {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
connection = DriverManager.getConnection(jdbcURL,user,password);
} catch (Exception e) {
e.printStackTrace();
}
return connection;
}
}
Also sometimes application shows this error:
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

I don't see any problem in your code. The problem is probably with your server hosting. You should check the country of the host provider and measure the time required to send a request to the server. Also you should use logger instead of System.out.println so you can examine required time for actions like db access, application logic and find a bottleneck.

"Invalid connection string format" error when trying to connect to Oracle using TNS alias that contains dot character

I am trying to connect to Oracle database using TNS.
The problem is that TNS alias contains dot, so when I am specifying url like this:
jdbc:oracle:thin:#TNS.ALIAS
I've got...
oracle.net.ns.NetException: Invalid connection string format, a valid format is: "host:port:sid"
...during creation of connection.
I know that dot character is a problem, because after removing it from tnsnames.ora file connection to database works.
My question is - is it possible to escape dot character somehow? Maybe there is some connection parameter that can be setup to allow dot character in alias? I would like to avoid removing dot from tnsnames.ora since i am getting the file from outside source.
Here are the options that I've already tried that gave me the same error:
jdbc:oracle:thin:#"TNS.ALIAS"
jdbc:oracle:thin:#\"TNS.ALIAS\"
jdbc:oracle:thin:#`TNS.ALIAS`
jdbc:oracle:thin:#TNS\.ALIAS - this one is not compiling
jdbc:oracle:thin:#TNS\\.ALIAS
jdbc:oracle:thin:#TNS.ALIAS
jdbc:oracle:thin:#TNS\".\"ALIAS
jdbc:oracle:thin:#TNS%2eALIAS
Here are the options that resulted with oracle.net.ns.NetException: could not resolve the connect identifier:
jdbc:oracle:thin:#TNSALIAS
jdbc:oracle:thin:#TNS-ALIAS
jdbc:oracle:thin:#TNS_ALIAS
Additional context:
I am trying to create Java's DataSource (OracleDataSource to be
strict) in Scala (it is Play Framework - but I am not using Play's
way of creation of DB connections - I am doing it manually)
I have SQL Developer that is using exactly the same tnsnames.ora file and it is working there
We are having C# applications that are using exactly the same tnsnames.ora file and it is working there (data source is defined like this: <add name="connectionName" connectionString="Data Source=TNS.ALIAS;"/>

You need set
System.setProperty("oracle.net.tns_admin","C:\\app\\product\\12.2.0\\client_1\\network\\admin");
set to the location of the tnsnames.ora
import java.sql.Connection;
import java.sql.DriverManager;
public class DBConnect {
public Connection connection;
public DBConnect() {
}
public void connect() throws Exception {
String connectString;
System.setProperty("oracle.net.tns_admin", "C:\\app\\product\\12.2.0\\client_1\\network\\admin");
Class.forName("oracle.jdbc.driver.OracleDriver");
connectString = "jdbc:oracle:thin:#esmdj.test";
System.out.println("Before DriverManager.getConnection");
try {
connection = DriverManager.getConnection(connectString, "scott", "tiger");
System.out.println("Connection established");
connection.setAutoCommit(false);
} catch (Exception e) {
System.out.println("Exception inside connect(): " + e);
e.printStackTrace();
}
}
public static void main(String[] args) {
DBConnect client = new DBConnect();
System.out.println("beginning");
try {
client.connect();
System.out.println("after Connected");
client.connection.close();
System.out.println("after close");
} catch (Exception e) {
try {
System.out.println("Exception : " + e);
client.connection.close();
e.printStackTrace();
} catch (Exception ex) {
System.out.println("Close Connection Exception : " + ex);
ex.printStackTrace();
}
}
}
}
C:\Program Files\Java\jdk1.8.0_73\bin>java -classpath . DBConnect
beginning
Before DriverManager.getConnection
Connection established
after Connected
after close
tnsnames.ora
esmdj.test =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = xxx.xxx.yyy.zzz)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = ESMD)
)
)

I've found the problem - I was using older Oracle driver (ojdbc7.jar for version 12.1.0.1) after change to newer one (ojdbc8.jar for version 12.2.0.1) lookup by TNS alias started to work - there was no need to escape anything

how can i handle multiple server MongoDB

Hi all i am new to spring maven project, and i am using MongoDB. I want to use two tomcats/ MongoDB both of theri IP address are different. when first DB is down i need to connect with second one how it is possible
I am using following code
public boolean mongoRunningAt(String uri) {
try {
Mongo mongo = new Mongo(new MongoURI(uri));
try {
Socket socket = mongo.getMongoOptions().socketFactory.createSocket();
socket.connect(mongo.getAddress().getSocketAddress());
socket.close();
} catch (IOException ex) {
mongo = new Mongo(new MongoURI(uri_second));
Socket socket = mongo.getMongoOptions().socketFactory.createSocket();
socket.connect(mongo.getAddress().getSocketAddress());
socket.close();
//return false;
}
mongo.close();
return true;
} catch (UnknownHostException e) {
return false;
}
}
Using this code i tried with first one successfully connected, now stoped first DB now restarted server it is connected with second db.
But if i didn't restart server it is always pointing to First only... how should i work on this
Thanks in advance

You deployed 2 servers, are they in a replica set. If not you can follow the link.
When they are already in a replica set you can use a connectionstring containing the 2 servers.
Like this:
mongodb://db1.example.net,db2.example.net:2500/?replicaSet=test