j'c'westlakestaffs'ac'uk

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JSP the update database problem

• Format of lecture
• The update a database problem
• Tackling the problem
• An update Guest JSP walkthrough
• Summary

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The update problem

• How to tackle for the assignment?
• What do we need to do? See below
• Steps
• Understand the SQL we can use
• What can we use we have developed already? See
  next slide
• Solution using the Guests example
• We need to
• Allow the user to select a guest record
• View it
• Modify it and write it back to the database i.e.
  update it
• Are there any aspects we dont wish to allow the
  user to do
• Yes they cannot alter the key in this case
  email address.

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The update problem

• What can we use that we have already developed?
• Answer lots
• We can modify the html form we used for selecting
  a guest to delete to be select a guest to update
• The html form can call a jsp which simply
  displays the result in a set of text boxes rather
  than a table format
• We can allow the user to change the content of
  the text box for firstname and lastname and then
  call a jsp to do the update to the database and
  then call another jsp to display the confirmation

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JSP code snippets

• To stop the key (email) text box being changed
• ltTABLE BORDER"1" WIDTH"50" ALIGN"center"
  BGCOLOR"lightgreen" CELLPADDING"2"gt ltTRgt
• ltTD WIDTH"25"gtltBgtEmaillt/Bgtlt/TDgt
• ltTD WIDTH"25"gtltINPUT TYPE"text" SIZE"25"
  READONLY"true" NAME"email" VALUE"lt email
  gt"gtlt/TDgt

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Next stage

• A JSP which can use the parameters from the
  update form and call a bean to update the
  database
• So required another JSP
• Copy and modify the AddGuests JSP see code
• A bean
• Copy and modify GuestBean
• Will have a method to update the database
• Use the Update SQL command
• String sql "UPDATE Guests SET
  GuestBook.firstName'" this.fName
  "',GuestBook.lastname this.lName "' WHERE
  email '" email "'"
• statement.executeUpdate(sql)

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Demo

• Now follows

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Your assignment

• You can use the same approach to modify an and
  update an order