将java.sql.Connection转换为PGConnection

Question

我想使用Tomcat在PostgreSQL中上传文件：

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

我尝试以这种方式投射conn对象：

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

我得到了

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

我也尝试过：

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

我得到了

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

LargeObjectManager pgCon = pgCon.getLargeObjectAPI();

实现代码的正确方法是什么？

P.S

我试过了：

PGConnection pgConnection = null;

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

LargeObjectManager lobj = pgConnection.getLargeObjectAPI();

但我在这一行LargeObjectManager lobj = pgConnection.getLargeObjectAPI();

获得了NPE

Answer 1

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

Answer 2

这对我来说很有效：

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();