Re: jdbc works in java app, fails in servlet: "no suitable jdbc found"
От | philfrei@aol.com |
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Тема | Re: jdbc works in java app, fails in servlet: "no suitable jdbc found" |
Дата | |
Msg-id | 8CCD29579E64490-22E4-8BA9@webmail-d019.sysops.aol.com обсуждение исходный текст |
Ответ на | Re: jdbc works in java app, fails in servlet: "no suitable jdbc found" (philfrei@aol.com) |
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Re: jdbc works in java app, fails in servlet: "no suitable
jdbc found"
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Список | pgsql-jdbc |
This is to follow up with the solution I was given at the Eclipse "Newbies" forum. Thank you Russell Bateman! With a right-click on the project, and a selection of "Properties," one can navigate to "Java EE Module Dependencies." At this point, one can "select the utility project, JAR or classpath entry to add as a Web Library dependency." One of the choices offered was in fact the PostgreSQL JDBC Driver library. After checking the option box, I was able to run the servlet and have it connect to the PostgreSQL database. A further clue (which I overlooked until this afternoon) was that in the "Markers" area was the following Classpath Warning: Classpath entry org.eclipse.datatools.connectivity.jdt.DRIVERLIBRARY/PostgreSQL JDBC Driver will not be exported or published. Runtime ClassNotFoundExceptions may result. Indeed, the problem was that the Driver class from the JDBC was not being found. But once the above checkbox was selected, the warning disappeared. Do I understand this, or all the suggestions given? Not a whole lot. I'm guessing that somehow the Apache server is executing code that is not referencing the usual Java packages and libraries, and it needs to have these dependencies addressed. I can't say the location for this is exactly intuitive. But then, I am totally new to this and maybe it will start to make more sense as I get further along. One person was asking why I have no WAR file. The code for this project was started from scratch and a bit of cut-and-paste. It was not created from a WAR and I have yet to package it into a WAR. Maybe that answers his question? Thanks again for everyone who took time to address this question! Phil Freihofner -----Original Message----- From: Craig Ringer <craig@postnewspapers.com.au> To: philfrei@aol.com Cc: pgsql-jdbc@postgresql.org Sent: Wed, Jun 2, 2010 7:19 pm Subject: Re: jdbc works in java app, fails in servlet: "no suitable jdbc found" On 3/06/2010 8:28 AM, philfrei@aol.com wrote: > Thank you for the reply! > >> You need to preload the PostgreSQL driver... > > Being new to this, I find myself second-guessing words as simple as > "preload". The servlet "NearbyTest" has a constructor and a single > method "doGet" which is invoked by an HTML page. As the first working > statement in the "doGet" method (at this point everything else is > commented out), I tried using the recommended statements. Both of them > elicited the same error message: > > try { > // Class.forName("org.postgresql.Driver"); > this.getClass().getClassLoader().loadClass("org.postgresql.Driver"); > } catch (ClassNotFoundException e1) { > e1.printStackTrace(); > } > > java.lang.ClassNotFoundException: org.postgresql.Driver I'd say your classpath is misconfigured; the classloader cannot find PostgreSQL. On web service containers sometimes the dependencies for the servelet must all be embedded in a .war with the serverlet jar. Is that the case here? > Is there another stage (prior to the servlet's > "doGet") at which the "preloading" should occur? Nope, just loading the class is sufficient. > The stack trace indicates code that is part of Apache. Is there possibly > something that has to be configured in Apache that is missing? Well the trace refers to org.apache.catalina.loader.WebappClassLoader , which is a part of Apache Catalina. It has nothing to do with the Apache web server except that they're both from the Apache project. Catalina is Tomcat's servlet container. That further suggests that you need to configure your classpath in your web app environment, or have an issue with how your app and dependencies are packaged. I've only done this stuff with Maven & Netbeans targeting Glassfish, so I can't really offer much help with the details of doing it right using Eclipse's build system and a Tomcat target. -- Craig Ringer
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