Обсуждение: Cannot create JDBC driver of class '' for connect URL 'null'

Hi,

I encounter a problem regarding setting up a JNDI Datasource at Tomcat
with PostgreSQL under Linux Suse 10.3 environment. This is the
exception.

org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC
driver of class '' for connect URL 'null'

I wonder if there are some additional settings that I may have
forgotten.

Would you give me a hand here?

Stanley



Here is what I do:

0) Ensure the postgreSQL.jar is stored inside the tomcat/lib

1) Create a context.xml in the META-INF. The context.xml defines the
context below:

<?xml version="1.0" encoding="UTF-8"?>
<Context path="/someApp" docBase="someApp"
   crossContext="true" reloadable="true" debug="1">

<Resource name="jdbc/postgres" auth="Container"
          type="javax.sql.DataSource"
driverClassName="org.postgresql.Driver"
          url="jdbc:postgresql://127.0.0.1:5432/testdb"
          username="gepguser" password="password" maxActive="20"
maxIdle="10"
maxWait="-1"/>
</Context>

Where testdb is the database inside PostgreSQL.

2) Add the following entry in web.xml:

      <resource-ref>
        <description>postgreSQL Datasource example</description>
        <res-ref-name>jdbc/postgres</res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
    </resource-ref>

3) Use the following code to get the connection:

    public Connection getConnection() {
        Connection conn = null;
        Context initCtx;
        try {
            initCtx = new InitialContext();
            DataSource ds = (DataSource) initCtx

.lookup("java:comp/env/jdbc/postgres");

            conn = ds.getConnection();
        } catch (NamingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return conn;
    }

Stanley Wong wrote:
> Hi,
>
> I encounter a problem regarding setting up a JNDI Datasource at Tomcat
> with PostgreSQL under Linux Suse 10.3 environment. This is the
> exception.
>
> org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot create JDBC
> driver of class '' for connect URL 'null'

Using your sample works for me with the changes indicated below.

>
> I wonder if there are some additional settings that I may have
> forgotten.
>
> Would you give me a hand here?
>
> Stanley
>
>
>
> Here is what I do:
>
> 0) Ensure the postgreSQL.jar is stored inside the tomcat/lib
>
> 1) Create a context.xml in the META-INF. The context.xml defines the
> context below:
>
> <?xml version="1.0" encoding="UTF-8"?>
> <Context path="/someApp" docBase="someApp"
>    crossContext="true" reloadable="true" debug="1">

Take out path and docBase.  Since you are defining a context, Tomcat
knows those.

> 3) Use the following code to get the connection:
>
>     public Connection getConnection() {
>         Connection conn = null;
>         Context initCtx;
>         try {
>             initCtx = new InitialContext();
>             DataSource ds = (DataSource) initCtx
>
> lookup("java:comp/env/jdbc/postgres");

You are missing a decimal point between initCtx and lookup.

Where are you running this code?  I created a sample JSP page dbtest.jsp
and placed it in the root directory of the context.  I called my context
text, so under that I had dbtest.jsp, META-INF and WEB-INF.  Since you
are creating the datasource within the context, only Java code running
within the context has access to it.

--
Guy Rouillier