java null pointer exception while running select query in kafka KSQL engine

Question

Steps :

1. We have created a Kafka topic called pgsqlcountry which has all the streaming data from postgreSQL DB.

2. we created a stream called country for processing the topic into a table.

3. stream was created successfully.

-

ksql> describe country;

Field      | Type
------------------------------
ROWTIME    | BIGINT
ROWKEY     | VARCHAR(STRING)
ID         | BIGINT
COUNTRY    | VARCHAR(STRING)
CREATED_AT | BIGINT
UPDATED_AT | BIGINT

-

4. we run the SQL command "select * from country"

5. we get error as below

-

ksql> select * from country;

null | null | null | null | null | null
Exception in thread "ksql_query_1-8f1f36a7-e83c-476d-8561-98fe9ed8866b-StreamThread-2" java.lang.NullPointerException

Please find my stacktrace in this screenshot

Answer 1

When I had java.lang.NullPointerException , I had incompatible versions of the ksqldb images.

There appears to be the cp prefix images, eg

• cp-ksqldb-server
• cp-ksqldb-cli

Don't mix and match with these images (try to stick with one group or the other):

• sqldb-server
• ksqldb-cli

You can run some other commands (eg SHOW PROPERTIES; ) and see if this also gives the same error of java.lang.NullPointerException . If it does, it probably is the image.