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From David Smith <d...@cornell.edu>
Subject Re: Datasource: Cannot load JDBC driver class 'com.mysql.jdbc.Driver'
Date Sun, 16 Sep 2007 18:24:13 GMT
Tomcat's database pooling implements a slightly refactored version of 
the Commons DBCP project -- packages were renamed to avoid conflicts 
should a developer decide to use the Commons DBCP library in their own 
app.  You can find a complete list of possible attributes for the 
Resource definition here:

http://commons.apache.org/dbcp/api-1.2.2/org/apache/commons/dbcp/BasicDataSource.html

Just look at the setters -- remove the word set from the beginning of 
the method name and drop the case on the first letter after 'set'.  For 
example, if you want access setValidationQuery(), you would drop set and 
lower case the V for validationQuery="" in your <Resource ../> definition.

--David

Ken Bowen wrote:
> David,
>
> Bingo!  Right on:  Changed all permissions (chown -R tomcat myapp), 
> and dropped the mysql jar from WEB-INF/lib, and
> it all works.  Many thanks!  I do hate it when I forget simple stuff 
> like permissions.  Moving things from Windows to *nix
> always does that to me.
> Side note question:  Am I correct that the following is the intended 
> xml?:
>
> <Resource name="jdbc/sb_data" auth="Container"
>               type="javax.sql.DataSource"
>                maxActive="100" maxIdle="30" maxWait="10000"
>                validationQuery="select 1"
>                username="sb_normal" password="********"
>                driverClassName="com.mysql.jdbc.Driver"
>                 url="jdbc:mysql://localhost:3306/sb_data"/>
>
> Where could I read more about these kinds of details?
>
> Thanks again,
> Ken Bowen
>
> David Smith wrote:
>> Don't 'copy' the mysql driver from WEB-INF/lib to 
>> TOMCAT_HOME/common/lib -- move it.  It cannot be in both places at 
>> once.  Also be sure the permissions are set correctly so tomcat can 
>> read the jar and be sure you've restarted tomcat after the move so 
>> the classloaders pick it up properly.  I have no idea why it works in 
>> Windows at all unless the Windows install has a copy of it in 
>> common/lib already -- which can cause problems later on if it's also 
>> in WEB-INF/lib.
>>
>> As a side note (and this is becoming a mantra with me) please don't 
>> use ?autoReconnect=true in your jdbc url.  Instead add the attribute 
>> validationQuery="select 1" in the Resource element.  That tells the 
>> pool how to validate the connection and optionally regenerate it 
>> before you borrow.
>>
>> --David
>>
>> Ken Bowen wrote:
>>> Hello,
>>>
>>> I'm working on a CENTOS 5 Linux setup.
>>> I'm trying to avoid the pre-loaded tomcat which was installed in 
>>> /usr/share/tomcat5.
>>> I downloaded (from apache) and installed tomcat5.5.25 and installed 
>>> it in /opt/tomcat5.
>>> I made sure the existing tomcat is not running and I renamed 
>>> /usr/share/tomcat5.
>>>
>>> I start it (the new tomcat) with /opt/tomcat5/bin/startup.sh and it 
>>> runs fine:
>>> Tomcat manager runs and I can start/stop the built-in apps.
>>>
>>> I have an app which I developed using tomcat5.5.9 on Windows, and I 
>>> am trying to
>>> transfer it to this Linux setting.
>>>
>>> I placed my exploded app in webapps.  The app wants to use a Mysql 
>>> database named sb_data.
>>> The same database as on Windows has been replicated in Mysql in the 
>>> Linux setup.
>>> I have the following context.xml in my META-INF folder:
>>>
>>>    <Context path="/myapp" docBase="myapp"
>>>                      debug="5" reloadable="true" crossContext="true">
>>>       <Resource name="jdbc/sb_data" auth="Container"
>>>    type="javax.sql.DataSource"
>>>                 maxActive="100" maxIdle="30" maxWait="10000"
>>>                 username="sb_normal" password="********"
>>>                 driverClassName="com.mysql.jdbc.Driver"
>>>                   
>>> url="jdbc:mysql://localhost:3306/sb_data?autoReconnect=true"/>
>>>    </Context>
>>>
>>> My application has a registered AppListener in which I establish the 
>>> DataSource
>>> in the contextInitialized method and use it to do some initial work 
>>> with the database:
>>>
>>>        System.out.println("MyApp AppListener: ENTER");
>>>        ....
>>>        Context envCtx = (Context) 
>>> initialContext.lookup("java:comp/env");
>>>
>>>        String key = "jdbc" + "/" + "sb_data";
>>>        DataSource ds = (DataSource)envCtx.lookup(key);
>>>        if (ds != null ){
>>>            DAOBaseData.setDataSource(ds);
>>>        }
>>>        ....
>>>        ...CALL to DAOBaseData.getConnection();  HERE
>>>        ....
>>>        System.out.println("MyApp AppListener: EXIT");
>>>
>>> The code for getConnection() looks like this:
>>>
>>>        public Connection getConnection() throws DAOException
>>>        {
>>>            Connection connection = null;
>>>            if (datasource!= null) {
>>>                try {
>>>                    connection = datasource.getConnection();
>>>                } catch (SQLException e) {
>>>                      //TODO: Log this
>>>                      String message = e.getMessage();
>>>                      System.out.println("DAOBaseData: "+message);
>>>                      throw new DAOException(message);
>>>                }
>>>            }
>>>            connCount++;
>>>            System.out.println("Connection[data] allocated: 
>>> #="+connCount);
>>>            return connection;
>>>        }
>>>
>>> This works ok on Windows, but in the Linux setting I get the 
>>> following error in
>>> the catalina.out log:
>>>
>>>        MyApp AppListener: ENTER
>>>        DAOBaseData: Cannot load JDBC driver class 
>>> 'com.mysql.jdbc.Driver'
>>>        com.myapp Error: Cannot load JDBC driver class
>>>    'com.mysql.jdbc.Driver'
>>>        MyApp AppListener: EXIT
>>>
>>> I'm using the mysql-connector-java-3.1.14-bin.jar and it is present 
>>> in WEB-INF/lib.
>>> I tried copying it to /opt/tomcat5/common/lib , but I still get the 
>>> same error.
>>>
>>> I'm confused.  Why does tomcat on Windows find the JDBC driver, but 
>>> not find it on Linux?
>>>
>>> Thanks in advance,
>>> Ken Bowen
>>>
>>>
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>>
>>
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>>
>
>
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