first connection attempt always fails, subsequent always succeed

This is an embedded tomcat application, not full-blown apache server.  Works great when it does...  I haven't wired in a connection supplier yet since (for now) there are few clients and they do two reads and one write, all very large.

java:

java -version
openjdk version "11.0.9" 2020-10-20
OpenJDK Runtime Environment (build 11.0.9+11-Ubuntu-0ubuntu1.20.04)
OpenJDK 64-Bit Server VM (build 11.0.9+11-Ubuntu-0ubuntu1.20.04, mixed mode, sharing)

tomcat: 

version 9.0.39

poostgres:

PostgreSQL 12.4

This is the servlet's connection code:

String templateUrl = System.getProperty("SGSSVR_databaseConnection", "jdbc:postgresql://%s/%s"); //host(with :port) / dbname
String fullurl = String.format(templateUrl, dbhost, dbname);  //will add port to this next
conn = DriverManager.getConnection(fullurl, dbrole, magicPassword);
dsl = DSL.using(conn, SQLDialect.POSTGRES);

which generates this stack trace, showing what looks to me like a good url (and which works later).

java.sql.SQLException: No suitable driver found for jdbc:postgresql://localhost/version4007
    at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:702)
    at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:228)
    at edu.utah.camplab.servlet.AbstractSGSServlet.setDbConn(AbstractSGSServlet.java:52)
    at edu.utah.camplab.servlet.ParfileServlet.doGet(ParfileServlet.java:30)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:834)