NullPointerException when we use craftsman.spy JDBC logging driver

[Mihai Dinca-Panaitescu]

We register the spy driver (http://zer0.free.fr/craftsman/spy.php) like:

System.setProperty("spy.driver", "net.ucanaccess.jdbc.UcanaccessDriver");
DriverManager.registerDriver(new SpyDriver());
System.setProperty("spy.log", "D:/logs/jdbc-spy.log");

When we try to connect we get:

java.lang.NullPointerException
at craftsman.spy.SpyConnection.getMetaData(SpyConnection.java:252)
at net.ucanaccess.jdbc.DBReference.getHSQLDBConnection(DBReference.java:346)
at net.ucanaccess.jdbc.UcanaccessDriver.connect(UcanaccessDriver.java:190)

meaning .getHSQLDBConnection returns null

[Marco Amadei]

The stacktrace you posted can't be generated by the situation you described, unless you're using a very out-of-date ucanaccess version. Please upgrade ucanaccess to the the latest version and send the resulting stacktrace again, along the jdbc url used (you omitted the call to the DriverManager).

[Mihai Dinca-Panaitescu]

Hi.

I call DriverManager.getConnection(...) . The ideea is the connection works when we do not register spy driver and it does not when we register it. I tested also with the last version and get :

java.util.concurrent.ExecutionException: net.ucanaccess.jdbc.UcanaccessSQLException: UCAExc:::3.0.3.1 nullnet.ucanaccess.jdbc.UcanaccessSQLException: UCAExc:::3.0.3.1 nulljava.lang.NullPointerException

UCAExc:::3.0.3.1 null
net.ucanaccess.jdbc.UcanaccessDriver.connect(UcanaccessDriver.java:260)
craftsman.spy.SpyDriver.connect(SpyDriver.java:265)
java.sql.DriverManager.getConnection(DriverManager.java:571)
java.sql.DriverManager.getConnection(DriverManager.java:215)
.....
null
craftsman.spy.SpyConnection.getMetaData(SpyConnection.java:252)
net.ucanaccess.jdbc.DBReference.getHSQLDBConnection(DBReference.java:444)
net.ucanaccess.jdbc.UcanaccessDriver.connect(UcanaccessDriver.java:227)
craftsman.spy.SpyDriver.connect(SpyDriver.java:265)
java.sql.DriverManager.getConnection(DriverManager.java:571)
java.sql.DriverManager.getConnection(DriverManager.java:215)
.....

The jdbc url used is like :
jdbc:ucanaccess://D:/Temp/access/test.accdb;showschema=true

[Marco Amadei]

Okay, I see. This time the stacktrace is meaningful. Once I have reproduced the issue within spy, I'll let you know my findings(today I can't, but hopefully tomorrow I should be able to).

[Marco Amadei]

Sorry for the late answer, this code works fine for me:

public static void main(String[] args) throws SQLException, ClassNotFoundException, InstantiationException, IllegalAccessException {
        System.setProperty("spy.driver", "net.ucanaccess.jdbc.UcanaccessDriver");
        DriverManager.registerDriver(new SpyDriver());
        System.setProperty("spy.log", "D:/jdbc-spy.log");
        Connection conn=DriverManager.getConnection("jdbc:spy:net.ucanaccess.jdbc.UcanaccessDriver:ucanaccess://C:\\db\\test.accdb");
        Statement st=conn.createStatement();
        ResultSet rs=st.executeQuery("select * from ab");
        while(rs.next()){
            ...
        }
        ...
    }

[Mihai Dinca-Panaitescu]

Hi.

Sorry to forget about this.

We do one more thing just before we register the Spy driver, we deregister all existing drivers , meaning ucanaccess driver is also unregistered:

            Enumeration<Driver> drivers = DriverManager.getDrivers();
            while (drivers.hasMoreElements()) {
                DriverManager.deregisterDriver(drivers.nextElement());
            }

and we use :

     Connection conn=DriverManager.getConnection("jdbc:ucanaccess://C:\\db\\test.accdb");

without spy.

We can connect like this to any jdbc driver we have (using the normal url) like oracle, mysql, postgresql, derby and so on, except ucanaccess.

[Marco Amadei]

Nothing wrong in the ucanaccess behaviour.
So, you deregister each driver forcing each connection be wrapped by spy. Unfortunately ucanaccess in turn wraps another driver: the hsqldb driver. In the wrapping chain spy-> ucanaccess-> spy-> hsqldb spy fails some association. Therefore spy invokes ucanaccess to connect to an hsqldb url(resulting in a null returned by ucanaccess and so in a NullPointerException).
You know, supporting this approach wouldn't be worth for me but...

Immediately after the drivers' deregistration, you have to re-re-register the hsqldb driver (which fortunately isn't in your list and so hopefully it's used just by ucanaccess):

DriverManager.registerDriver(new org.hsqldb.jdbc.JDBCDriver());
Those young java hackers...

[Mihai Dinca-Panaitescu]

Yes. It makes sense if a driver uses another driver. I will do as suggested.