Challenge – Part 3

Goal: Implement the update functionality.

Task 1

Every update button inside the table must make a GET request to the homepage.

th:href="@{/}"

Task 2

Every item that gets submitted should carry an id.

public class Item {
    //...
    private String id;

    public Item() {
        this.id = UUID.randomUUID().toString();
    }

    public String getId() {
        return this.id;
    }

    public void setId(String id) {
        this.id = id;
    }

    //...

}

Upon pressing update, the GET request needs to include an id parameter that identifies the selected item.

 th:href="@{/(param = ${element.field})}"

Submit another item to the inventory table. Then, press update.

Output: the parameter should get carried over

Print the id inside the handler method, and repeat the process.

public String getForm(Model model, @RequestParam(required = false) String id) {
    //...
    System.out.println("id: " + id);
    //...
    return "form";
}

Terminal Output: id: 5500b7d3-73ac-4d1d-9596-1b5bbca3cae1

Task 3

Before returning the form view, check if the id matches any of the items inside the data store.

public String getForm(Model model, @RequestParam(required = false) String id) {
    
                  // if there is a match
    if (match) {  
        model.addAttribute("item", matching object);
    } 

    else {      // if there is no match
        model.addAttribute("item", new Item());
    }

     //etc...
}

In there is a match, your form elements will pre-populate with values from the model attribute.

Task 4

1. Upon form submission, make sure the id is part of the POST request payload.

<input type="hidden" th:field="*{YOUR_ID_FIELD}">

2. (Optional): Inside handleSubmit(), confirm that the item's id is being received.

3. Use the id to check if the submitted item already exists

   • If so, your handler method must update the datastore.
   • Otherwise, your handler method must add to the datastore.

4. Redirect the client to the inventory view.

5. Test both scenarios before moving to the next task.

Task 5

FlashAttribute: Data that survives a redirect.

Inside Constants.java, create another constant called SUCCESS_STATUS.

public static final String SUCCESS_STATUS = "success";

Inside handleSubmit(), add the following parameter:

(Item item, RedirectAttributes redirectAttributes)

Before redirection, add a FlashAttribute with key: status and value: Constants.SUCCESS_STATUS.

redirectAttributes.addFlashAttribute("status", Constants.SUCCESS_STATUS);

After redirecting the client to /inventory, the FlashAttribute will populate Model model.

    @GetMapping("/inventory")
    public String getInventory(Model model)

Task 6

Display the following div only if status equals success.

    <div class="alert success">
        <strong> You successfully submited the item! </strong> 
    </div> 

Task 7

Your next task is to forbid updates if the new orderDate has a 5-day discrepancy from the previous one.

Inside Constants.java, create another constant called FAILED_STATUS.

public static final String FAILED_STATUS = "failed";

The following method returns true if two dates are within 5 days.

    public boolean within5Days(Date newDate, Date oldDate) {
        long diff = Math.abs(newDate.getTime() - oldDate.getTime());
        return (int) (TimeUnit.MILLISECONDS.toDays(diff)) <= 5;
    }

The next step is to update handleSubmit()

    @PostMapping("/submitItem")
    public String handleSubmit(Item item, RedirectAttributes redirectAttributes) {


    }

1. The status variable starts off equaling success.

    @PostMapping("/submitItem")
    public String handleSubmit(Item item, RedirectAttributes redirectAttributes) {

        int index = getIndexFromId(item.getId());   

        /****************** 1 ******************/

        String status = Constants.SUCCESS_STATUS;

2. If the id doesn't have a match, the submitted item gets added to the datastore.

    @PostMapping("/submitItem")
    public String handleSubmit(Item item, RedirectAttributes redirectAttributes) {

        int index = getIndexFromId(item.getId());   

        /****************** 1 ******************/

        String status = Constants.SUCCESS_STATUS;

        /****************** 2 ******************/

        if (index == Constants.NOT_FOUND) {
            items.add(item);
        }

3. If there is a match, and the updated date is within 5 days, the datastore gets updated.

    @PostMapping("/submitItem")
    public String handleSubmit(Item item, RedirectAttributes redirectAttributes) {

        int index = getIndexFromId(item.getId());   

        /****************** 1 ******************/

        String status = Constants.SUCCESS_STATUS;

        /****************** 2 ******************/

        if (index == Constants.NOT_FOUND) {
            items.add(item);
        }

        /****************** 3 ******************/

        else if (within5Days(item.getDate(), items.get(index).getDate())){
            items.set(index, item);
        }

4. If there is a match, but the updated date is not within 5 days, nothing happens and the status variable equals failed.

    @PostMapping("/submitItem")
    public String handleSubmit(Item item, RedirectAttributes redirectAttributes) {

        int index = getIndexFromId(item.getId());   

        /****************** 1 ******************/

        String status = Constants.SUCCESS_STATUS;

        /****************** 2 ******************/

        if (index == Constants.NOT_FOUND) {
            items.add(item);
        }
        /****************** 3 ******************/

        else if (within5Days(item.getDate(), items.get(index).getDate())){
            items.set(index, item);
        }


        /****************** 4 ******************/

        else {
            status = Constants.FAILED_STATUS;
        }

        redirectAttributes.addFlashAttribute("status", status);
        return "redirect:/inventory";
    }

---

HTML

Add a Thymeleaf attribute that displays the div only if the status attribute equals failed.

     <div class="alert">
          <strong > You failed to submit the item. </strong> 
     </div>

Finally, try updating an item's date beyond the 5-day threshold.

Good Luck!