Develop Reference

How to connect to Oracle9i with SQLDeveloper 21?

I want to connect to an old Oracle9i Release 9.2.0.4.0 database with SQLDeveloper 21.4.3 and I followed this answer How to change default JDBC driver of Oracle SQL Developer?.
The difference is just the versions of SQLDeveloper (21 instead of 20) and Oracle Instant Client (21.3 instead of 11.2.0.4.0). In my case both are the latest ones.
My OS is also Windows 10, 64bit.
Testing the client and connection as described are successful. But when actually connecting to the database SQLDeveloper hangs and can only be closed by TaskManager.
I tried both connection types: simple and with user defined URL jdbc:oracle:thin:#172.31.10.3:1521:LZH. This URL works in other applications like SQL Workbench/J using oracle driver ojdbc14_g.jar.
I also tried to set this jar file in SQLDeveloper preferences as external jdbc driver. But I guess here only non oracle drivers like postgreSQL make sense, but don't know. It doesn't make a difference anyway.
Thanks for any suggestion!

You cannot connect an Oracle Client version 21 to an (more than 20 years old) Oracle 9i database. See Client / Server Interoperability Support Matrix for Different Oracle Versions
Maybe ask Oracle support to get an older version of SQL Developer.

Oracle provided me a link for older
Instant Client Versions.
Version 11.2 works fine with SQLDeveloper 20.2.
SQLDeveloper 21 only supports client versions 19 and higher.

tomcat 8.5.x tomcat-jdbc.jar vs official oracle ojdbc6.jar driver

I'm struggling with jdbc connection to oracle database, which should I use?
The tomcat-jdbc.jar (inside tomcat) or oracle ojdbc6.jar (official by oracle)
What are the difference between the two driver?
(ojdbc6 version 11.2.0.4 guarantee to me to work with oracle 12c db and oracle 10 db could do the same the tomcat-jdbc.jar??)

Actually, they are different libraries. tomcat-jdbc.jar is the default Tomcat connection pool (in Tomcat version 8.5) and it's responsible for managing connections, allowing you fast access to already created ones, whereas ojdbc6.jar is your actual JDBC driver from Oracle that provides database connectivity to Oracle Database server.
Other words, you cannot use tomcat-jdbc.jar alone in case you want to "talk" to your Oracle Database, but it's possible to use ojdbc6.jar without pooling, although it's not recommended due to perfomance drop in most cases.
Here is a good explanation:
ojdbc6.jar -
What is ojdbc6.jar file?
Connection Pool - https://en.wikipedia.org/wiki/Connection_pool

How to connect to Oracle Database 12c HR schema from IntelliJ IDEA 14

I am new in Oracle Database. I have successfully done these:
Installed and configured Oracle Database 12c in Windows 10 VMware virtual machine.
Connected to HR schema from SQL*PLUS, SQL Developer, Navicat.
Created a ASP.NET web application project and connected to HR schema from Visual Studio 2015.
Now I want to connect to HR schema through JDBC from IntelliJ IDEA 14. Unfortunately I cannot connect though I have installed JDBC drivers. I have read the reference here but it does not work. I am getting the following error:
Connection to Oracle - HR#localhost failed
java.sql.SQLException: Listener refused the connection with the following error:
ORA-12514, TNS:listener does not currently know of service requested in connect descriptor
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:489)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:553)
...
For better demonstration, a screenshot is attached. Notice that I cannot define the service name (in this case "pdborcl") because there is no text field for this in Data Sources and Drivers window. Also notice that I can still connect to HR schema through SQL*PLUS after the error.
How to resolve this issue? Or, is it an IntelliJ IDEA bug or a JDBC bug?

You should be using "pdborcl" in the Database field. That is your service name, HR is just a schema in it.

Getting JDBC drivers compatibility issue. java.sql.SQLException: ORA-06413: Connection not open

I am getting below exception with Oracle JDBC ojdbc14_g.jar drivers:
java.sql.SQLException: ORA-06413: Connection not open.
My Oracle version is:
My machine and server details are:
I am able to connect to production DB from my development environment, but after installing application in production server my application is unable to connect to locally installed database. I am getting above said exception.
Below is my connection URL:
jdbc:oracle:oci8:#127.0.0.1:1521:XE

Try to replace oci8 with thin. JDBC over (native) OCI require some knowledge and experience. You have to install and configure Oracle client 1st.
See http://docs.oracle.com/cd/B28359_01/java.111/b31224/instclnt.htm

Error while connecting to Oracle DSN using Java

I need to develop an application that connects to various DSN's using the Microsoft ODBC drivers. I have developed the application in Eclipse and it seems to work properly. The connection succeeds and I am able to view table data.
However when I export the project to a runnable jar file (using Eclipse) the functionality fails for Oracle. It is unable to establish connectivity with the Oracle connection string. It still works for SQL server but fails in case of Oracle. I'm unable to figure out the cause as the same ODBC drivers are being used for both Oracle and SQL-Server. More mystifying is that it runs properly on Eclipse. Since im using the ODBC drivers I don't believe the problem is because of an external jar file.
The driver is sun.jdbc.odbc.JdbcOdbcDriver and connection string is like jdbc:odbc:oratest;user=fell;password=pass.
I'm getting the following exception
java.sql.SQLException: [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified
at sun.jdbc.odbc.JdbcOdbc.createSQLException(JdbcOdbc.java:6958)
Can you please help me figure what the problem might be?
Thanks in advance,
Fell

Create a System DSN.
java.sql.Connection cn;
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
cn=java.sql.DriverManager.getConnection("jdbc:odbc:dsn_name","user","pass");

Check the classpath in the eclipse project