Re: loading jdbc Driver in servlet

On 12/17/18 4:26 AM, Dave Cramer wrote:
>
>
> On Mon, 17 Dec 2018 at 02:28, Thomas Kellerer <spam_eater(at)gmx(dot)net
> <mailto:spam_eater(at)gmx(dot)net>> wrote:
>
> Rob Sargent schrieb am 14.12.2018 um 19:28:
> > Using java 1.8, postgresql-42.1.4.jar, embedded tomcat 9
> >
> > It appears to me that I need to make the call
> > "Class.forName("org.postgresql.Driver)" when the entry is in a
> > servlet.  Is this expected, within a servlet, or is this just /post
> > hoc ergo propter hoc /at it finest and I changed something else
> > (wittingly or not).  Same code outside of servlet does not need the
> > forced loading of the class and the manual claims it's not need
> after
> > java 1.6
>
> Class.forName() is definitely not needed if the driver's JAR file is
> included in the classloader of the class requesting a connection.
>
> Where exactly did you put the JDBC driver's jar file?
> And what exactly is your main() method doing?
>
> If you look at Tomcat's startup script (catalina.sh or
> catalina.bat), it's
> obvious that setting up the claspath isn't that straightforward.
> My guess is, that that your main() method does something different
> and does not properly include the driver's jar in the classpath.
>
>
>
> Servlet classpath issues are legendary. As Thomas points out setting
> up the classpath for a servlet engine is not trivial.
>
>
As I've manage to get down the road using "forName()" this becomes
largely academic.

The classpath of the main does have postgres.

Using this

    System.out.println("main classpath: \n" + getClasspathString());

    private String getClasspathString() {
        StringBuffer classpath = new StringBuffer();
        ClassLoader applicationClassLoader =
this.getClass().getClassLoader();
        if (applicationClassLoader == null) {
            applicationClassLoader =
ClassLoader.getSystemClassLoader();
        }
        java.net.URL[] urls =
((java.net.URLClassLoader)applicationClassLoader).getURLs();
        for(int i=0; i < urls.length; i++) {
classpath.append(urls[i].getFile()).append("\n");
        }
        return classpath.toString();
    }

I get:

main classpath:
/home/u0138544/gits/java/gitlab/gtdb/tport/build/libs/tport.jar
/home/u0138544/gits/java/gitlab/gtdb/tools/build/libs/tools.jar
/home/u0138544/gits/java/gitlab/gtdb/sgs/build/libs/sgs.jar
/home/u0138544/.m2/repository/org/slf4j/slf4j-api/1.7.7/slf4j-api-1.7.7.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/org.postgresql/postgresql/42.1.4/1c7788d16b67d51f2f38ae99e474ece968bf715a/postgresql-42.1.4.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/net.sf.jopt-simple/jopt-simple/4.9/ee9e9eaa0a35360dcfeac129ff4923215fd65904/jopt-simple-4.9.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/javax.servlet/javax.servlet-api/3.1.0/3cd63d075497751784b2fa84be59432f4905bf7c/javax.servlet-api-3.1.0.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/javax.servlet/javax.servlet-api/3.1.0/3cd63d075497751784b2fa84be59432f4905bf7c/javax.servlet-api-3.1.0.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/javax.xml.bind/jaxb-api/2.2.12/4c83805595b15acf41d71d49e3add7c0e85baaed/jaxb-api-2.2.12.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/org.apache.tomcat.embed/tomcat-embed-core/9.0.12/136c8dc5c84e82bf2d68bb10648d4fa8b402184/tomcat-embed-core-9.0.12.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/org.apache.tomcat.embed/tomcat-embed-el/9.0.12/8ee44bee76043321860cde871cf6343de1483ff5/tomcat-embed-el-9.0.12.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/org.apache.tomcat.embed/tomcat-embed-jasper/9.0.12/f81c352450b9695b73b90b3e5ef78d6f7fcb1a96/tomcat-embed-jasper-9.0.12.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/org.apache.tomcat.embed/tomcat-embed-logging-juli/9.0.0.M6/2b083aa89d92ce10356158da1e643f8a8e890b49/tomcat-embed-logging-juli-9.0.0.M6.jar
/home/u0138544/.gradle/caches/modules-2/files-2.1/org.apache.tomcat/tomcat-annotations-api/9.0.12/dfda698ec20b257a6801a2df25c76554658f6005/tomcat-annotations-api-9.0.12.jar
/home/u0138544/work/test/gtdb/

That is generated inside the run() method, as my main() is a Runnable
(perhaps unnecessarily so, I'm in the midst of a migration from handling
sockets myself to letting Tomcat do that work.  I'm embedding Tomcat to
make the footprint just a little more streamlined (or maybe obfuscated).

Inside the servlet the classpath is:

Servlet classpath:
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/classes/
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/groovy-all-2.4.7.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jaxb-api-2.2.12.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/tomcat-embed-logging-juli-9.0.0.M6.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jpsgcs-3.1.1-2.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jackson-annotations-2.9.8.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/tools.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/logback-classic-1.1.2.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/logback-access-1.1.2.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jackson-core-2.9.8.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jooq-3.11.7.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/logback-core-1.1.2.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jooq-codegen-3.11.7.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/tomcat-embed-core-9.0.12.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jackson-databind-2.9.8.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/tomcat-annotations-api-9.0.12.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/postgresql-42.1.4.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jooq.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/sgs.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jopt-simple-4.9.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/longpowerset-1.0.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/slf4j-api-1.7.7.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/anno.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/javax.servlet-api-3.1.0.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/tport.jar
file:/home/u0138544/work/test/crashpad/monitor/webapp.war*/WEB-INF/lib/jooq-meta-3.11.7.jar

Happy to let this be part of the servlet classpath legend!