Including external jars after launching Pyspark in Jupyter notebook - jar

Question

I have been trying in vain to include external jars into pyspark/Jupyter notebook env after the notebook has been launched. (Alternatively, the jars are included successfully either with:
1. Use --jar ojdbc6.jar
2. include the jar in spark-defaults.conf )
I have tried below all failed:
Idea 1:
import pyspark
from pyspark.sql import SparkSession
spark = SparkSession \
.builder \
.appName("testjars") \
.config("spark.jars", "C:\\Users\\U620311\\ojdbc6.jar") \
.config("spark.driver.extraClassPath", "C:\\Users\\U620311\\ojdbc6.jar") \
.config("spark.executor.extraClassPath", "C:\\Users\\U620311\\ojdbc6.jar") \
.getOrCreate()
spark.sparkContext._conf.getAll()
Invoke jar file as below:
DB_USER = ""
DB_PASS = ""
DB_DRIVER = "oracle.jdbc.driver.OracleDriver"
JDBC_URL = "<connection string>"
query = '''(select * from <tablename>) t1'''
ojdbcDF = (sqlContext.read.format("jdbc").option("driver", DB_DRIVER).option("url", JDBC_URL).option("dbtable", query).option("user", DB_USER).option("password", DB_PASS).load())
Idea 2:
I have played with all permutations. Include extraclasspath but not spark.jars and vice versa. no success.
Idea 3:
import os
os.environ['PYSPARK_SUBMIT_ARGS'] = '--jars ojdbc6.jar pyspark-shell'
import pyspark
sc.stop()
sc = pyspark.SparkContext()
from pyspark.sql import SQLContext
sqlContext = SQLContext(sc)
DB_USER = "<uid>"
DB_PASS = "<pwd>"
DB_DRIVER = "oracle.jdbc.driver.OracleDriver"
JDBC_URL = "<connection string>"
query = '''(select * from <tablename>) t1'''
ojdbcDF = (sqlContext.read.format("jdbc").option("driver", DB_DRIVER).option("url", JDBC_URL).option("dbtable", query).option("user", DB_USER).option("password", DB_PASS).load())
All of the above lead to the same error message. Would you please help in identifying if there is missing configuration or missing code. Please suggest an alternatives to try.
Py4JJavaError: An error occurred while calling o373.load.
: java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at org.apache.spark.sql.execution.datasources.jdbc.DriverRegistry$.register(DriverRegistry.scala:38)
at org.apache.spark.sql.execution.datasources.jdbc.JDBCOptions$$anonfun$6.apply(JDBCOptions.scala:78)
at org.apache.spark.sql.execution.datasources.jdbc.JDBCOptions$$anonfun$6.apply(JDBCOptions.scala:78)
at scala.Option.foreach(Option.scala:257)
at org.apache.spark.sql.execution.datasources.jdbc.JDBCOptions.<init>(JDBCOptions.scala:78)
at org.apache.spark.sql.execution.datasources.jdbc.JDBCOptions.<init>(JDBCOptions.scala:34)
at org.apache.spark.sql.execution.datasources.jdbc.JdbcRelationProvider.createRelation(JdbcRelationProvider.scala:32)
at org.apache.spark.sql.execution.datasources.DataSource.resolveRelation(DataSource.scala:330)
at org.apache.spark.sql.DataFrameReader.load(DataFrameReader.scala:152)
at org.apache.spark.sql.DataFrameReader.load(DataFrameReader.scala:125)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:244)
at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:357)
at py4j.Gateway.invoke(Gateway.java:280)
at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:132)
at py4j.commands.CallCommand.execute(CallCommand.java:79)
at py4j.GatewayConnection.run(GatewayConnection.java:214)
at java.lang.Thread.run(Thread.java:748)