[CONJ-443] NullpointerException when making concurrent procedure calls Created: 2017-03-09  Updated: 2017-03-30  Resolved: 2017-03-30

Status: Closed
Project: MariaDB Connector/J
Component/s: Other
Affects Version/s: 1.5.8
Fix Version/s: 2.0.0-RC, 1.6.0

Type: Bug Priority: Major
Reporter: Jonathan Stringer Assignee: Diego Dupin
Resolution: Fixed Votes: 1
Labels: None

Attachments: PNG File Screen Shot 2017-03-15 at 3.10.46 PM.png    

 Description   

I am making the same call to a store procedure multiple times with very little change in the arguments. The first call succeeds but the second call creates a null pointer exception.

The problem is caused at line 487 of MariaDbConnection class. That is when the callableStatementCache is adding a new callableStatement. That callableStatement has a the sql field populated but the value for the items that is added to the callableStatementCache has null sql field. When that value is fetched on line 479 the clone fails with a NullPointerException because the sql field cannot be null.

Below is the stack trace.
java.lang.NullPointerException
at org.mariadb.jdbc.MariaDbServerPreparedStatement.prepare(MariaDbServerPreparedStatement.java:143) at org.mariadb.jdbc.MariaDbServerPreparedStatement.clone(MariaDbServerPreparedStatement.java:134) at org.mariadb.jdbc.AbstractCallableProcedureStatement.clone(AbstractCallableProcedureStatement.java:99) at org.mariadb.jdbc.MariaDbProcedureStatement.clone(MariaDbProcedureStatement.java:119) at org.mariadb.jdbc.MariaDbProcedureStatement.clone(MariaDbProcedureStatement.java:62) at org.mariadb.jdbc.MariaDbConnection.prepareCall(MariaDbConnection.java:479) at com.zaxxer.hikari.pool.ProxyConnection.prepareCall(ProxyConnection.java:289) at com.zaxxer.hikari.pool.HikariProxyConnection.prepareCall(HikariProxyConnection.java)

 Comments   
Comment by Jochen Bedersdorfer [ 2017-03-15 ]

The only NPE that can be thrown here is if `protocol` is null.
And AFAIK this can only happen if the statement has been closed.

            serverPrepareResult = protocol.prepare(sql, mustExecuteOnMaster);

Comment by Jochen Bedersdorfer [ 2017-03-16 ]

See screenshot. Breakpoint triggered on protocol == null.
Not sure how closed statements made it into the pool - or remained there.

Comment by Jochen Bedersdorfer [ 2017-03-16 ]

Work-around: disable callable prep stmt cache. Add this to your JDBC-URL:
cacheCallableStmts=false

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