Cannot cast from ConnectionWrapper to oracle.jdbc.OracleConnection using JAVA1.8 and Tomcat 8.5.28

问题

Why connection is not working after few seconds? Application is hanging up and not running as expected and returning the below error.

java.lang.ClassCastException: org.apache.commons.dbcp.PoolingDataSource$PoolGuardConnectionWrapper cannot be cast to org.apache.tomcat.dbcp.dbcp2.DelegatingConnection

Below is the code that is used to get the connection:

OracleConnection oracleConnection = (OracleConnection) 
((DelegatingConnection)connection).getInnermostDelegate();

using libraries: commons-pool1.6.jar for encryption & tomcat-dbcp.jar for database.

Using encrypted username and password in Tomcat context.xml.

Also, using accessToUnderlyingConnectionAllowed=true in context.xml file.

Issue is with JAVA8 and Tomcat8. Able to work properly with plain credentials, the only issue happens with encrypted credentials.

回答1:

You shouldn't do casting or unwrapping. Use correct DataSource type in Tomcat 'conf/context.xml' file. In case of Oracle it is: oracle.jdbc.pool.OracleDataSource. Set also correct driver and factory. Look at this example of mine:

<Context>

<!-- Default set of monitored resources. If one of these changes, the    -->
<!-- web application will be reloaded.                                   -->
<WatchedResource>WEB-INF/web.xml</WatchedResource>
<WatchedResource>WEB-INF/tomcat-web.xml</WatchedResource>
<WatchedResource>${catalina.base}/conf/web.xml</WatchedResource>

<!-- Uncomment this to disable session persistence across Tomcat restarts -->
<!--
<Manager pathname="" />
-->
<Resource name="UNCUNC"
          auth="Container"
          type="oracle.jdbc.pool.OracleDataSource"
          factory="oracle.jdbc.pool.OracleDataSourceFactory"
          driverClassName="oracle.jdbc.OracleDriver"

          url="jdbc:oracle:thin:@p260unc4.big.ru:1566:uncunc"
          user="dsserv"
          password="dsservPass" 

          connectionProperties="SetBigStringTryClob=true"
          maxTotal="20" maxIdle="10"
          maxWaitMillis="-1"/>              
<JarScanner scanManifest="false"/>

Later in the java code use it like this (don't cast):

try {
        Context initContext = new InitialContext();
        Context envContext  = (Context)initContext.lookup("java:/comp/env");
        DataSource ds = (DataSource)envContext.lookup("UNCUNC");
    } catch (NamingException e) {
        logger.error("DATASOURCE error", e);
    }
 Connection conn = ds.getConnection();

Should work just fine. Take attention in different versions of Tomcat you need to use 'username' instead 'user' field.

来源：https://stackoverflow.com/questions/52161264/cannot-cast-from-connectionwrapper-to-oracle-jdbc-oracleconnection-using-java1-8

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