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Java servlet and MySQL error  RSS feed

 
Greenhorn
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I wrote the site, there should in the table bring the name of the students from the database (MySQL) + I can add the name of the new student to the database through the table and delete it. I wrote a servlet and JSP, but for some reason it does not work.

My Servlet (with requests)




JSP - AddStudent



JSP delete Student




Web XML

 
Marshal
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Hi Steve, welcome to the Ranch!

I didn't understand what you meant by "didn't work" -- that's not very specific. It would help if you explained what was supposed to happen, and what happened instead, and showed us what error messages appeared, and other things like that.

However I decided to give the code a quick scan and I noticed this:



So yes, that code does actually bring in the names of the students. However it doesn't do anything with the names.

But that really doesn't matter yet because it's in the show() method, and you never call that method.

And you mentioned a JSP: the one you posted has a form which sends a student's name via the POST method. However the doPost() method of your servlet doesn't have any code which adds a student to the database.

Also I noticed in your web.xml that your servlet isn't in a named package. Servlets must be in a named package.

There's likely more problems beyond that -- I think you have written far too much code before testing anything. I would suggest starting again with something simpler: perhaps a servlet which just outputs the names of the students?
 
Steve Gates
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Paul Clapham wrote:Hi Steve, welcome to the Ranch!

I didn't understand what you meant by "didn't work" -- that's not very specific. It would help if you explained what was supposed to happen, and what happened instead, and showed us what error messages appeared, and other things like that.

However I decided to give the code a quick scan and I noticed this:



So yes, that code does actually bring in the names of the students. However it doesn't do anything with the names.

But that really doesn't matter yet because it's in the show() method, and you never call that method.

And you mentioned a JSP: the one you posted has a form which sends a student's name via the POST method. However the doPost() method of your servlet doesn't have any code which adds a student to the database.

Also I noticed in your web.xml that your servlet isn't in a named package. Servlets must be in a named package.

There's likely more problems beyond that -- I think you have written far too much code before testing anything. I would suggest starting again with something simpler: perhaps a servlet which just outputs the names of the students?






Thank You)


I have already written a separate project and there he displays the names of the students.

Please can help write the code so that it prints the first and last names of students from my SQL database, and I can also add and remove students from the database.
 
Paul Clapham
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Sure, we can help. But display-add-remove requires several servlets, although you could get away with only one JSP. So my suggestion was to start with one servlet, namely the one which displays the students.

Actually the first thing you should do is to design the JSP. So perhaps you could start with that? You won't be able to test it without writing a servlet, but as you may know, in computer programming it's better to design first and write code later.
 
Steve Gates
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Unfortunately, only one servlet is needed and there should be these requests
 
Paul Clapham
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Steve Gates wrote:Unfortunately, only one servlet is needed and there should be these requests



You want only one servlet but your requirements are that you need to be able to add students AND remove students? No, you should have a servlet which does nothing but add a student (and then forwards to a JSP which redisplays the remaining students). And you should have another servlet which does nothing but remove a student (and then forwards to that same JSP). That's just a basic design principle -- a component should do only one thing. If that "only one servlet" idea is coming from somebody else and you are being forced to do it that way, then I feel sorry for you.

Anyway, you already have my suggestion. Let me just add one thing more: you don't have to write the whole system before you start testing the code you wrote.
 
Steve Gates
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Please, you can write your version of the project.
 
Paul Clapham
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No. That's not how the Ranch works. We aren't a code-writing service -- but we're definitely willing help people with code that they have written. So give it a try and then come back and ask about the code you've written.
 
Steve Gates
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The project that I wrote above cannot be corrected at all?
 
Paul Clapham
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You may remember that I pointed out several problems with it already.
 
Sheriff
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I merged your stuff with the following thread. I hope that is okay by you.
 
Steve Gates
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I want to delete it through its id

MyServlet



Delete JSP

 
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What does "I can't" mean? How are you executing any of this code, and what exactly happens as a result?
 
Steve Gates
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I change code

I can not delete a student from the database by id
My servlet
 
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Do you get an error?
 
Tim Moores
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Tim Moores wrote:What does "I can't" mean? How are you executing any of this code, and what exactly happens as a result?



TellTheDetails
 
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