CODEWITHSUNDEEP
javamysqleclipsejdbcconnection
vagg77
vagg77

Reputation: 97

Connection object returns null values

Im trying to create a class that will allow me to connect to mySQL DB via JDBC but the object that Connection returns is null. I believe that the error is that I do not use error information messages inside the Exceptions but instead return null values.

Removing the return null; statement caused an error: This method must return a result of type Connection

    return conn;
} catch (Exception e) {
  // return null;
   e.printStackTrace();
   }

}

Adding both return null; and e.printStackTrace(); caused an Unreachable code error 

    return conn;
} catch (Exception e) {
   return null;
   e.printStackTrace();
   }

My code :

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class ServerConn
{
public Connection OpenDatabase() {
    try {
    Class.forName( "com.mysql.jdbc.Driver" ) ;
    Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/promitheas?user=me&password=iwontsay") ;
        return conn;
    } catch (Exception e) {
       return null;
    }
    }

    public ResultSet dbQuery(String sql)
    {
    Connection cn = OpenDatabase();
     if (!(cn == null)){
       try {
         Statement stmt = cn.createStatement();
         ResultSet rs = stmt.executeQuery(sql);
         return rs;
        } catch (Exception e) {
       return null;}
    }
    return null;
    }

    public ServerConn(){}
    }

Upvotes: 1

Views: 3860

Answers (2)

Shailesh Aswal
Shailesh Aswal

Reputation: 6802

its better (less confusing) to use a single return statement. 

 public Connection OpenDatabase() {
      Connection conn =null;
        try {
         Class.forName( "com.mysql.jdbc.Driver" ) ;
         conn  = DriverManager.getConnection("jdbc:mysql://localhost/promitheas?user=me&password=iwontsay") ;
         } catch (Exception e) {
                  e.printStackTrace();
         }
         return conn;//returns null in case of exception.
  }

Upvotes: 1

Suresh Atta
Suresh Atta

Reputation: 121998

    return conn;
} catch (Exception e) {
   return null; //returning
   e.printStackTrace(); // what should I do as you are already returning.
   }

That is illeagal. And causes Unreachable code error, Since you are writing code after return

    return conn;
} catch (Exception e) {
   e.printStackTrace();
    return null;
   }

Besides that returning from catch block is smelling like a design issue. Rethink of it once.

Upvotes: 1

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