When enabling jndi connection pooling with java, you have to set just this context property
// Enable connection pooling
env.put("com.sun.jndi.ldap.connect.pool", "true");
But if you’re using SSL, Anonimous bind or MD5 auth, you have to specify some System properties too
com.sun.jndi.ldap.connect.pool.protocol="plain ssl"
com.sun.jndi.ldap.connect.pool.authentication="none simple DIGEST-MD5"
or ssl, anonymous and md5 connections will be excluded from the pool
info here