Error initializing TransactionManager. Could not instantiate TransactionConfig

Question

After migrating from Java 6 to Java 8 and from jboss 6.2 to jboss 7.2 i'm encountering the following problem:

Caused by: com.ibatis.sqlmap.client.SqlMapException: Error initializing TransactionManager.  Could not instantiate TransactionConfig.  Cause: java.lang.NullPointerException
    at com.ibatis.sqlmap.engine.builder.xml.SqlMapConfigParser$7.process(SqlMapConfigParser.java:192) [ibatis-2.3.4.jar:]
    at com.ibatis.common.xml.NodeletParser.processNodelet(NodeletParser.java:121) [ibatis-2.3.4.jar:]
    ... 138 more
Caused by: java.lang.NullPointerException
    at org.jboss.as.naming.InitialContext.getURLScheme(InitialContext.java:162) [wildfly-naming-7.2.9.GA-redhat-00003.jar:7.2.9.GA-redhat-00003]
    at org.jboss.as.naming.InitialContext.getURLOrDefaultInitCtx(InitialContext.java:130) [wildfly-naming-7.2.9.GA-redhat-00003.jar:7.2.9.GA-redhat-00003]
    at javax.naming.InitialContext.lookup(InitialContext.java:417) [rt.jar:1.8.0_322]
    at javax.naming.InitialContext.lookup(InitialContext.java:417) [rt.jar:1.8.0_322]
    at com.ibatis.sqlmap.engine.transaction.jta.JtaTransactionConfig.setProperties(JtaTransactionConfig.java:47) [ibatis-2.3.4.jar:]
    at com.ibatis.sqlmap.engine.builder.xml.SqlMapConfigParser$7.process(SqlMapConfigParser.java:183) [ibatis-2.3.4.jar:]
    ... 139 more

This the code:

        private Ibatis() throws MyException {
                try {
            String resource = "com/tact/raqu/ibatis/sqlmaps/SqlMapConfigRaqu.xml";
            Reader reader = Resources.getResourceAsReader(resource);
            sqlMap = SqlMapClientBuilder.buildSqlMapClient(reader);
                } catch (Exception e) {
            log.error("Errore di configurazione Ibatis", e);
            throw new QuasarException("Errore di configurazione Ibatis", e);
            }
    }

and here the xml

<sqlMapConfig>
    <settings useStatementNamespaces="false"
            cacheModelsEnabled="true"
            enhancementEnabled="true"   
            lazyLoadingEnabled="true" />                    
    <typeHandler javaType="java.util.Calendar" callback="com.tact.raqu.dao.CalendarTypeHandler"/>
   <transactionManager type="JTA">
        <property name="transactionManagerName" value="java:jboss/TransactionManager"/>
        
        <dataSource type="JNDI">
            <property name="DataSource" value="java:/jdbc/ds_raqu"/>
        </dataSource>
    </transactionManager>
    <sqlMap resource="com/tact/raqu/ibatis/sqlmaps/raqu.xml"/>
</sqlMapConfig>

the null pointer is on a class of the ibatis framework as it tries to do a lookup at userTransaction, if I add the following line to the xml:

property name="UserTransaction" value="java:jboss/UserTransaction"/>

gives the error:

WFLYEJB0137: Only session and message-driven beans with bean-managed transaction demarcation are allowed to access UserTransaction.

But i need to use cmt. Any helps?

switching transactionManagement type from JTA to EXTERNAL makes it work, but i have to use JTA.