first you will check network name and after you will give correct username and password it will connect.
My network name is correct and both the username and password is correct. By the way, I can connect to the database through PL/SQL developer. But I really need this Oracle SQl developer SQL data modeler is for data model diagram. Any help?
What version of SQL Developer are you using?
What does the relevant section of your TNSNAMES file?
Do you have other databases you can try to connecting to? Do they show the same error.
I can see hints elsewhere that this is a syntax error in the JDBC connection string. It isn't specific to SQL Developer or even Oracle JDBC. No one seemed to have an answer for any the questions that I found by googling.
As a workaround you could use a basic connection and extract the host, port , sid/service entries from the tnsnames.ora