Chapter 3b: JSP Basics 2 Sessions

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Chapter 3b JSP Basics 2 Sessions JSPs
Reference Beginning JSP
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Objectives

• To learn
• Decoding incoming URL parameters
• Sessions and JSPs
• Scoping of implicit objects in JSP
• Shopping Cart Example
• Adding a Shopping Cart
• Rendering order information
• Using a session to track line items

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Simple Web Storefront

• Shopping Cart Example

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Add Shopping Cart to Catalog

• Reference Example 2 (page 90)
• Add a BUY hyperlink to estore.jsp
• lta href"lt request.getContextPath()
  /example2/shopcart.jsp?actionbuysku"
  curItem.getSku() gt"gt
• ltbgtBUYlt/bgt lt/agt
• Hyperlinks URL
• Calls shopcart.jsp
• Two Parameters
• action buy (from estore.jsp), inc (from
  shopcart.jsp)
• sku items sku (of product selected)

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Decoding Incoming Parameters

• Decoding incoming URL parameters in shopcart.jsp
• lt
• int quan 1 // defaults to 1 if not
  specified in URL
• String action request.getParameter("action")
  
• if (action.equals("inc"))
• String oldQuan request.getParameter("quan")
  
• quan Integer.parseInt(oldQuan)
• quan
• // else - actionbuy
• gt
• Check for null parameters
• lt
• String sku request.getParameter("sku")
• Product item null
• if (sku ! null)
• item EShop.getItem(sku)
• gt

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Increment and Return to Home Links

• Add 1 hyperlink in shopcart.jsp
• lta href"lt request.getContextPath() EXAMPLE
  CART_PAGE "?actionincquan" quan "sku"
  sku gt"gt
• ltbgtAdd 1lt/bgtlt/agt
• Alternative Use request.getRequestURL() if
  calling the same JSP page
• Return hyperlink to return to estore.jsp
• lta href"lt request.getContextPath() EXAMPLE
  SHOP_PAGE gt"gt
• Return to Shoppinglt/agt

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Overcoming Cart Limitations

• Reference Example 3 (page 100)
• To remember what has been ordered
• Add a Java class named LineItem
• Properties quantity, sku, description, price
• In shopcart.jsp
• Check if list of line items already exists in
  session object
• ArrayList items (ArrayList) session.getAttribute
  ("lineitems")
• Create and store ArrayList of LineItems objects
  collection to session object
• if (items null) // add first item Buy
  link from estore.jsp
• items new ArrayList()
• items.add(new LineItem(1,sku,prod.getName(),
• prod.getPrice() ))
• session.setAttribute("lineitems", items)

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Clear Cart and Increment

• Clear Cart hyperlink in shopcart.jsp
• lta href"lt request.getContextPath() EXAMPLE
  CART_PAGE "?actionclear" gt"gt
• Clear the cartlt/agt
• Executing Clear Cart action
• else if (action.equals("clear"))
• items.clear()
• Add 1 (increment) action
• for (int i0 iltitems.size() i)
• LineItem curItem (LineItem)
  items.get(i)
• if (curItem.getSku().equals(sku))
• itemFound true
• curItem.setQuantity(curItem.getQuant
  ity() 1)
• break
• // of if
• //of for

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Calculate and Display Total Price

• Calculate Total Price
• lt
• for (int i0 ilt items.size() i)
• LineItem curItem (LineItem) items.get(i)
• int quan curItem.getQuantity()
• long price curItem.getPrice()
• long extended quan price
• total extended
• gt
• Rendering total order price
• lttd align"right"gtlt dispPrice(String.valueOf(tot
  al)) gtlt/tdgt

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Scoping of Implicit Objects in JSP

• Reference page 112
• pageContext
• Accessible within the current page
• request
• Accessible from all JSP pages that service the
  same request
• session
• Accessible from all the session-aware JSP pages
  that are accessed within the same session.
• application
• Accessible within all the JSP pages within the
  application. This is the global scope.

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Application Scope Example

• Reference examplex (page 113)
• In showglob.jsp
• lt
• ArrayList cats (ArrayList)
  application.getAttribute("cats")
• for (int i0 ilt cats.size() i)
• Category curCat (Category)
  cats.get(i)
• gt
• lt curCat.getName() gt
• ltbr/gt
• lt
• gt
• Note You must run estore.jsp first
• public void jspInit()
• getServletContext().setAttribute("cats",
  EShop.getCats())

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Next Steps

• Try It Out sections of Textbook (Chapter 3)
• Example 2, 3 and X
• Learn to use the NetBeans 4.1 Debugger
• Exercises 1 and 2 (Chapter 3)