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ArrayDescriptor and Oracle 11g JDBC driver

This month I have a lot of things to post about GAE, jOOQ, GWT, MVPP, but so little time to write them. In the meantime I want to share a little tip about a strange error message we had last year during the migration of a large number of J2EE web applications from Oracle 9i to 11g (well, the project context was bigger than a mere database migration, but the error occurred was due to the migration only). Part of these applications used to invoke PL/SQL functions and stored procedures on Oracle databases.

Oracle JDBC for 11g introduced an important difference from the 9i release in the oracle.sql.ArrayDescriptor usage. Every time you need to pass an Array of data from a Java web application to an Oracle stored procedure you have to use an oracle.sql.ARRAY object. In order to create it, before you have to create an instance of oracle.sql.ArrayDescriptor this way:

ArrayDescriptor descriptor = ArrayDescriptor.createDescriptor("CUSTOM_TYPE_ARRAY", conn);

were CUSTOM_TYPE_ARRAY is a custom type defined in the Oracle schema used by the web application and conn is an instance of oracle.jdbc.driver.T4CConnection. In a web application this connection underlies in a pooling data source and so you need to get it previously through reflection using the getInnermostDelegate method:


Method delegateMethod = 
             conn.getClass().getSuperclass().getMethod("getInnermostDelegate", new Class[0]);
if(delegateMethod != null) {
conn = (Connection) delegateMethod.invoke(conn, new Object[0]);
} 

But simply moving to JDBC for 11g (no change in the application code and the stored procedures) this doesn’t work anymore. Trying to create the new instance of ArrayDescriptor you obtain the following exception:


java.sql.SQLException: Fail to construct descriptor: Invalid arguments
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:113)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:147)
at oracle.sql.ArrayDescriptor.createDescriptor(ArrayDescriptor.java:144)
at oracle.sql.ArrayDescriptor.createDescriptor(ArrayDescriptor.java:115)

The exception thrown doesn't explain the real cause and is misleading: so people could waste a lot of time going in a wrong direction.
This error happens because the internal implementation of the oracle.sql.ArrayDescriptor class is almost totally different from JDBC 9i to JDBC 11g and Oracle introduced a further access restriction in the new release.
The solution is the following: you have to simply set the accessToUnderlyingConnectionAllowed property of the application data source to true (if not specified the default is false) in the application context.xml file. Example:


<Resource name="dsDataSourceNT" auth="Container"
     type="javax.sql.DataSource" username="UserName" password="XXXXXXX"
     driverClassName="oracle.jdbc.driver.OracleDriver"
     url="jdbc:oracle:thin:@DBServer:1612:SID5"
     maxActive="16" maxIdle="8" maxWait="60000"
     validationQuery="SELECT 1 FROM DUAL"
    accessToUnderlyingConnectionAllowed="true"
/>



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