将java.sql.Connection转换为PGConnection

Question

I want to upload a file in PostgreSQL using Tomcat:

@Resource(name = "jdbc/DefaultDB")
private DataSource ds;
Connection conn = ds.getConnection();

I tried to cast the conn object this way:

PGConnection pgCon = ((org.apache.commons.dbcp.DelegatingConnection) conn).getInnermostDelegate();

I get

Caused by: java.lang.ClassCastException: org.apache.tomcat.dbcp.dbcp2.PoolingDataSource$PoolGuardConnectionWrapper cannot be cast to org.postgresql.PGConnection

I also tried:

Connection unwrap = conn.unwrap(Connection.class);
connSec = (org.postgresql.PGConnection) unwrap;

I get

java.sql.SQLException: Cannot unwrap to org.postgresql.PGConnection

LargeObjectManager pgCon = pgCon.getLargeObjectAPI();

What is the proper way to implement the code?

PS

I tried this:

PGConnection pgConnection = null;

if (conn.isWrapperFor(PGConnection.class))
{
    pgConnection = conn.unwrap(PGConnection.class);
}

LargeObjectManager lobj = pgConnection.getLargeObjectAPI();

But I get NPE at this line LargeObjectManager lobj = pgConnection.getLargeObjectAPI();

Answer 1

if (dataSource.getConnection().isWrapperFor(PGConnection.class)) {
  PGConnection pgConnection = dataSource.getConnection().unwrap(PGConnection.class);
}

Answer 2

For me this worked:

if (conn.isWrapperFor(org.apache.tomcat.dbcp.dbcp2.DelegatingConnection.class))
        org.postgresql.jdbc.PgConnection pgConnection=(org.postgresql.jdbc.PgConnection)((org.apache.tomcat.dbcp.dbcp2.DelegatingConnection)conn).getInnermostDelegateInternal();