无法为连接URL''创建类''的JDBC驱动程序

Question

I'm using Tomcat 7.0.12 and receiving this error whenever I attmept to access a JNDI datasource connecting to a postgresql db via a .jsp page in a webapp called 'ROOT':

SEVERE: Servlet.service() for servlet [jsp] in context with path [] threw exception
[java.lang.RuntimeException: Cannot create JDBC driver of class '' for connect URL 'null'] with root cause
java.lang.NullPointerException
at sun.jdbc.odbc.JdbcOdbcDriver.getProtocol(JdbcOdbcDriver.java:507)
at sun.jdbc.odbc.JdbcOdbcDriver.knownURL(JdbcOdbcDriver.java:476)
at sun.jdbc.odbc.JdbcOdbcDriver.acceptsURL(JdbcOdbcDriver.java:307)
at java.sql.DriverManager.getDriver(DriverManager.java:253)
at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createConnectionFactory(BasicDataSource.java:1437)
at org.apache.tomcat.dbcp.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1371)
at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)

The postgresql JDBC driver is in my CATALINA/lib folder.

Here is my META-INF/context.xml:

<?xml version="1.0" encoding="UTF-8"?>

<Context>

<Resource name="jdbc/webdbro" auth="Container" type="javax.sql.DataSource"
    driverClassName="org.postgresql.Driver" url="jdbc:postgresql://127.0.0.1:5432/webdb"
    username="webdbro" password="pass" maxWait="-1" removeAbandoned="true" removeAbandonedTimeout="30"/>

<Resource name="jdbc/webdbrw" auth="Container" type="javax.sql.DataSource"
    driverClassName="org.postgresql.Driver" url="jdbc:postgresql://127.0.0.1:5432/webdb"
    username="webdbrw" password="pass" maxWait="-1" removeAbandoned="true" removeAbandonedTimeout="30"/>

<Resource name="jdbc/shadowdbro" auth="Container" type="javax.sql.DataSource"
    driverClassName="org.postgresql.Driver" url="jdbc:postgresql://127.0.0.1:5432/shadowdb"
    username="shadowdbro" password="pass" maxWait="-1" removeAbandoned="true" removeAbandonedTimeout="30"/>

</Context>

Here is my WEB-INF/web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<display-name>ROOT</display-name>

<resource-ref>
    <description>Read only webdb connector.</description>
    <res-ref-name>jdbc/webdbro</res-ref-name>
    <res-type>javax.sql.DataSource</res-type>
    <res-auth>Container</res-auth>
</resource-ref>
<resource-ref>
    <description>Read write webdb connector.</description>
    <res-ref-name>jdbc/webdbrw</res-ref-name>
    <res-type>javax.sql.DataSource</res-type>
    <res-auth>Container</res-auth>
</resource-ref>
<resource-ref>
    <description>Read only shadow db connector.</description>
    <res-ref-name>jdbc/shadowdbro</res-ref-name>
    <res-type>javax.sql.DataSource</res-type>
    <res-auth>Container</res-auth>
</resource-ref>

<welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
</welcome-file-list>

</web-app>

The weird thing is that I have 2 other webapps running on the same Tomcat server using the exact same configuration (web.xml and context.xml) so they can use the JNDI method to connect to the database and BOTH of those webapps work perfectly fine - I can query and update the database with no problems or exceptions in those apps. TIA...

Answer 1

In order to get all 3 webapps to use the same datasource properly, I had to move all my <Resource> entries from the META-INF/context.xml folder into the server's $CATALINA_BASE/conf/context.xml folder. Not a great solution, but it works.

Answer 2

我遇到了同样的问题，结果是我在context.xml上的<Resource>名称声明与web.xml上<resource-ref> name上定义的名称声明不匹配。

Answer 3

As answered above, one solution is to move the entries to $CATALINA_BASE/conf/context.xml

Another approach is described here: http://blogs.agilefaqs.com/2009/11/23/cannot-create-jdbc-driver-of-class-for-connect-url-null/

In particular, "Copy the Context.xml file to tomcat/conf/Catalina/localhost folder and renaming it to <web_app_name>.xml "

The underlying cause could be due to a problem with file permissions: "The user under which tomcat was running did not have permission to write to these folders. So we changed the group ownership of tomcat and /etc/tomcat folder to the same group to which the tomcat user belonged and magically everything started working as before."

This solution seems 'cleaner' to me because you can then have your entire web app including database connection properties wrapped up in a .war file.