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Struts & Hibernate
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| | | DB Connection prob | DB Connection prob 2007-03-20 - By Richard Yee
Back
Graeme,
Which application server are you using? Typically, each application
server has a built-in connection pool. Tomcat uses the Apache DBCP
http://jakarta.apache.org/commons/dbcp/
http://tomcat.apache.org/
You can find information on the sites for configuring it. Once you
configure it, you will use code similar to this to get a connection:
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InitialContext context = null;
Context envContext = null;
DataSource ds = null;
Connection conn;
try {
context = new InitialContext();
envContext = (Context) context.lookup(?java:comp/env?);
ds = (DataSource) envContext.lookup(?jdbc/myDataSource?);
conn = ds.getConnection();
} catch (NamingException ne) {
// log the naming exception
} catch (SQLException sqle) {
// handle the SLQ exception (log)
}
.
.
.
try {
/// use the connection
} catch (SQLException sqle) {
}
finally {
// close your resultset and statements, etc. and you connection
conn.close();
}
-Richard
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Graeme McLaren wrote:
> Hi there Richard, thank you for your reply. I'll give the final keyword a
> go. With respect to:
>
>> If this is so, your application is not going to be thread-safe b/c the
>> connection is static and can be used by different threads. If this is
>> for a
>> web application, you should use a connection pool and a datasource
>
> I have been doing a java course and this is my first web app outwith the
> course material (thread safe connections have never been mentioned in the
> course). I don't know anything about connection pools/datasources
> where can
> I find a good tutorial or good newbie info on this?
>
> What problems will be be caused by using the non thread safe
> connection as
> it is at the moment? I'm thinking performance problems.
>
>
> Thank you again for your reply.
>
> Graeme :)
>
>
>> From: Richard Yee <ryee@(protected)>
>> Reply-To: A mailing list about Java Server Pages specification and
>> reference <JSP-INTEREST@(protected)>
>> To: JSP-INTEREST@(protected)
>> Subject: Re: DB Connection prob
>> Date: Mon, 19 Mar 2007 21:44:14 -0700
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>>
>> Graeme,
>> Since you mention that you are using a deployment descriptor, I am
>> assuming this is for a web application. If this is so, your application
>> is not going to be thread-safe b/c the connection is static and can be
>> used by different threads. If this is for a web application, you should
>> use a connection pool and a datasource. In your current problem, your
>> variables should not be final.
>>
>> -Richard
>>
>> Graeme McLaren wrote:
>>> Hi all, I have a prob connecting to my Oracle DB. I have a class called
>>> "DBConnection" and have various setter methods which set values found
>>> in the
>>> deployment descriptor, for example:
>>>
>>> public static void setDriver (String val) {
>>> driver = val;
>>> System.out.println("driver 2= "+driver); // I get the value
>>> displayed here so all is good at this point
>>> }
>>>
>>> I then have a getConnection method within this class:
>>>
>>> public static Connection getConnection(){
>>> try{
>>> Class.forName( driver ); // load the JDBC "driver" class
>>> connection = DriverManager.getConnection( dbURL, username,
>>> password );
>>> // get connection
>>>
>>> /*
>>> more code here
>>> */
>>>
>>> } // end of getConnection
>>>
>>>
>>>
>>> When I try to call getConnection() I get a nullpointerexception at
>>> Class.forName( driver ); as "driver" is set to null, why is this
>>> when the
>>> setter method sets the value?
>>>
>>> All variables are declared set to null and are static so they should
>>> be able
>>> to be set by the setter method shouldn't they? Just thinking about it
>>> now
>>> I'm thinking that when the variables are initialised to "null" that is
>>> them
>>> set and cannot be changed because they are static (and final), would
>>> that be
>>> right?
>>>
>>> How should I fix this?
>>>
>>>
>>> Cheers
>>>
>>> Graeme :)
>>>
>>> ===========================================================================
>>>
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>>>
>>
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>
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Some relevant archives, FAQs and Forums on JSPs can be found at:
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