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- [Instructor] This is the UI mockup

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that we looked at earlier

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when we discussed requirement validation.

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In this mockup when we choose search from homepage,

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it takes us to a Search page

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where we enter some string based on which

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it pulls the products and then nutrients.

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When I select a different product,

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the nutrient table below also changes

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to reflect new set of nutrients.

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This markup helps us in thinking about the flow,

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which will now help us draw a sequence.

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We already know the sequence for initial data loading,

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which we worked through in the previous chapter.

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The food product and nutrients data

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are available in DAO in the form of product

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and nutrient maps.

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From here, our use case starts

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when the user chooses the search link on index JSP.

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Index JSP then forwards the request

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to search controller servlet.

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Search controller forwards the request

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to search inputs JSP,

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where user gets the option to enter a search string.

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Our search is currently very simple.

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So, all we have is one search box.

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But in future springs,

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we may offer options such as search by nutrient

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or ingredient or brand owner and so on.

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User sees the search box and enters a search string.

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Search input JSP received the search string

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and forwards it to search products servlet.

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The job of this servlet is to now connect with DAO

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and get search results.

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Since DAO has all the data,

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we can ask DAO to perform the search and return the results.

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Now, for all this to happen,

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we need some mechanism of passing the search string

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and search results among the JSPs and servlets.

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One approach is to use session variables.

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In this approach,

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the search products servlet get the session

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from the request

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and saves search string as a session attribute,

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then it asks DAO to search for products

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that have the search string in their names.

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DAO looks them up in its product map,

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and then returns a list of products

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that have the search string in their names.

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Now, if you recall our UI mockup,

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the first product in the list is selected by default,

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and its nutrients

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are displayed just beneath the product list.

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That means we need to search for first products nutrients.

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So now, the search product servlet makes another request

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to DAO this time

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to search what nutrients in the first product.

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DAO performs the search

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and then returns the list of nutrients.

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The search servlet has the search string,

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the product list, the list of nutrients,

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and the selected product, which is by default,

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the first product.

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It saves all these as session attributes

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and forwards the request to search results JSP for display.

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At this point, you can see that by tracing this flow,

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we have identified two new JSPs,

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search inputs and search results,

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and two new servlets,

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search controller and search product.

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You will also notice that this entire flow

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is shown in a loop,

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indicating that user can go back

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to input a new search as many times as needed.

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There is just one functionality missing in this workflow.

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And that is, user can select a different product

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from the product list.

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At that point, the search results

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should show a different list of nutrients,

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and not the nutrients for the first product

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which was selected by default.

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That means we need to have search results JSP,

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respond to a user's product selection based on

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which it needs to then change the nutrients display.

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And for that we can get a FDC ID of the selected product

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from radio button in search results JSP.

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It can then submit the form to another servlet,

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say, search nutrients.

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This servlet will then ask DAO

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to find nutrients for the product,

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get the list of nutrients,

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update the nutrients list session attribute

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and forward the request to search results

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for displaying the new set of nutrients.

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And for that we can get FDC ID of the selected product

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from radio buttons in search results JSP

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and submit the form to another servlet,

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say, search nutrients.

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This servlet will then ask DAO

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to find nutrients for the product,

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get the list of nutrients,

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update the nutrients list session attribute,

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and forward the request to search results

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for displaying the new set of nutrients.

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And once again, all this can happen in a loop

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where the user continues to select a different product

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from the search results,

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and the nutrient list keeps changing.

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So, with all these classes

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and their interaction traced out in a sequence diagram,

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we have this class diagram,

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where there are three new servlets

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and two new methods in DAO,

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that perform all the search we need.

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Also, I have now written out the hashCode

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and equals method in product class,

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as we need to compare objects for searching.

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With all this, we are now set to look at the code.