Runtime exception while creating Blob

Question

Trying to create BLOB object using BLOB.createTemporary(connection, false, BLOB.DURATION_SESSION) ,But getting Class Cast Exception

java.lang.ClassCastException: org.apache.commons.dbcp.cpdsadapter.ConnectionImpl cannot be cast to oracle.jdbc.OracleConnection.

I tried following suggestions but still same error .Apache Commons DBCP connection object problem, Thread: ClassCastException in org.apache.tomcat.dbcp.dbcp.PoolingDataSource$PoolGuardConnectionWrapper

Some one please suggest me to resolve this issue.

BLOB blob = BLOB.createTemporary(delConn, false, BLOB.DURATION_SESSION); Exception :java.lang.ClassCastException: org.apache.commons.dbcp.cpdsadapter.ConnectionImpl cannot be cast to oracle.jdbc.OracleConnection — user3376818
– user3376818, Commented Sep 2, 2015 at 22:55
So your program is one line long? What is the type of "delConn"? — OldProgrammer
– OldProgrammer, Commented Sep 2, 2015 at 23:00

Andreas · Accepted Answer · 2015-09-02 23:14:00Z

1

The Oracle BLOB.createTemporary() method expects the Connection parameter to be a oracle.jdbc.OracleConnection object, but connections from Tomcat are managed by DBCP, so the connection is wrapped in a DBCP class (org.apache.tomcat.dbcp.dbcp.PoolingDataSource$PoolGuardConnectionWrapper).

You either need to unwrap it to get the real Oracle connection object, or stop using the Oracle BLOB.

Just use the JDBC methods: Blob blob = connection.createBlob()

Update

The JDBC Blob is an interface. There are no implementing classes in the JDK, so you'll always get a DBMS specific implementation. If needed, you can cast to OracleBlob, which is also an interface, that provides additional Oracle-specific methods.

Interesting javadoc for OracleBlob:

Generally any new code should avoid the direct use of the class BLOB. For variable declarations use the interface Blob or this interface as required. Instead of the static methods BLOB.createTemporary(java.sql.Connection, boolean, int) and BLOB.empty_lob() please use Connection.createBlob() and BLOB.getEmptyBLOB() respectively.

edited Sep 2, 2015 at 23:14

answered Sep 2, 2015 at 22:59

Andreas

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14 Comments

user3376818 Over a year ago

Thanks Andreas, How to unwrap it.

user3376818 Over a year ago

Is there any difference in using JDBC Blob over Oracle BLOB

Andreas Over a year ago

First option: Don't. You'll be casting to internal Tomcat classes, so your code will only work with Tomcat, and may break on next Tomcat version.

Andreas Over a year ago

JDBC Blob will work with all DBMS's. Don't know if there are any negative sides.

user3376818 Over a year ago

I tried Blob getting exception : Exception in thread "Thread-4" java.lang.AbstractMethodError: oracle.jdbc.driver.T4CConnection.createBlob()Ljava/sql/Blob; at org.apache.commons.dbcp.DelegatingConnection.createBlob(DelegatingConnection.java:571)

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