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write into pdf file using binary data stored in database  RSS feed

 
Greenhorn
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(Edit: I added code tags so the code would be more readable -- Paul C)










. please tell me how to write some more content into pdf through before save onto disk
 
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You would probably need some sort of library for creating PDF documents. Googling "Java PDF API" results in a number of commercial products (although many are still free of charge to use).

A couple of pointers on your servlet and databases, though. All the code inside your doGet method is going to be run with every request. Typically when you have a resource like a database driver, you only want to initialize once, and not with every request. Take a look at the Servlet.init(...) method -
If you must declare a database driver in this way, no sense re-declaring it with every request.

Another problem is that you're declaring the Connection as a member of your servlet. Then with each request, you're re-opening it, and never closing it. This will quickly lead to memory leaks and other performance problems. In general, your database connection should not outlive the request.


 
Sheriff
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Pete Nelson wrote:A couple of pointers on your servlet, though. All the code inside your doGet method is going to be run with every request. Typically when you have a resource like a database driver, you only want to initialize once, and not with every request. Take a look at the Servlet.init(...) method -



"Initialize once"... yes, that's true. But in real life you would get a database connection from a connection pool configured into the servlet container. Having a database connection which belongs to a specific servlet also has its own problems as a design: it isn't thread-safe and it doesn't scale to the case where several servlets need database connections.
 
Pete Nelson
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Paul Clapham wrote:But in real life you would get a database connection from a connection pool configured into the servlet container.



You bet - using DataSources & JNDI is certainly the better approach. There were a lot of issues with the code provided, but I had to stop somewhere! I actually had a reply about three times the length, and just decided it was too much to hit the guy with all at once (Especially when his question was really about creating a PDF).
 
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