Lab 4: Using Spring Beans to Compose the UI

As you have seen in Lab 3 we have a lot of duplication between the UserManagementComponent and the GroupManagementComponent ViewComponent.\

We start by creating anLayoutComponent in de.tschuehly.easy.spring.auth.web.layout. We have a ViewContext parameter and the modal-related constants.

LayoutComponent.java

@ViewComponent
public class LayoutComponent {

  public static final String MODAL_CONTAINER_ID = "modalContainer";
  public static final String CLOSE_MODAL_EVENT = "close-modal";

  public record LayoutContext(ViewContext content) 
    implements ViewContext {}

  public ViewContext render(ViewContext content) {
    return new LayoutContext(content);
  }
}

In the template, we define the shared HTML between the pages.

LayoutComponent.jte

@import static de.tschuehly.easy.spring.auth.web.layout.LayoutComponent.CLOSE_MODAL_EVENT
@import static de.tschuehly.easy.spring.auth.web.layout.LayoutComponent.MODAL_CONTAINER_ID
@import de.tschuehly.easy.spring.auth.web.layout.LayoutComponent.LayoutContext
@param LayoutContext layoutContext

<html lang="en">
<head>
    <title>Easy Spring Auth</title>
    <link rel="stylesheet" href="/css/sakura.css" type="text/css">
    <script src="/htmx_1.9.11.js"></script>
    <script src="/htmx_debug.js"></script>
    <script src="http://localhost:35729/livereload.js"></script>
</head>
<body hx-ext="debug">
<nav>
    <h2>
        Easy Spring Auth
    </h2>
</nav>
<main>
    ${layoutContext.content()}
</main>
</body>
<div id="${MODAL_CONTAINER_ID}"
     hx-on:$unsafe{CLOSE_MODAL_EVENT}="this.innerHTML = null">
</div>
</html>

Now we can use the LayoutComponent in the GroupController and UserController.

We autowire the LayoutComponent and the GroupTableComponent and call their render method in the endpoint method:

GroupController.java

public static final String GROUP_MANAGEMENT =  "/group-management";

@GetMapping(GROUP_MANAGEMENT)
public ViewContext groupManagementComponent(){
  return layoutComponent.render(groupTableComponent.render());
}

In the UserController we autowire the LayoutComponent and the UserTableComponent and call their render methods in the endpoint method.

UserController.java

public static final String USER_MANAGEMENT_PATH = "/";

@GetMapping(USER_MANAGEMENT_PATH)
public ViewContext userManagementComponent() {
  return layoutComponent.render(userTableComponent.render());
}

We can now navigate to localhost:8080 and localhost:8080/group-management and both pages still work.

Lab-4 Checkpoint 1

If you are stuck you can resume at this checkpoint with:

git checkout tags/lab-4-checkpoint-1 -b lab-4-c1

But as we now see, there is no longer a navigation bar. The UserManagementComponent and the GroupManagementComponent are not used anymore. Instead, we can use them to define the page links displayed in the Navigation Bar.

We start by creating an Page interface in de.tschuehly.easy.spring.auth.web. We define a NavigationItem record and a navigationItem method.

Page.java

public interface Page {
  record NavigationItem(String displayName, String URI){}

  NavigationItem navigationItem();
}

We can now slim down the UserManagementComponent that defines the NavigationItem and the path to the Endpoint. We can also delete the UserManagementComponent.jte template.

UserManagementComponent.java

@Component
public class UserManagementComponent implements Page {

  @Override
  public NavigationItem navigationItem() {
    return new NavigationItem("User Management", UserController.USER_MANAGEMENT_PATH);
  }
}

We now need to fix CLOSE_MODAL_EVENT and the MODAL_CONTAINER_ID in the UserRowComponent and UserTableComponent .

We replace the incorrect imports with imports to the LayoutComponent

Now in the LayoutComponent, we can use Autowiring to get all Pages as a List and aggregate all NavigationItems into a List and pass it into the ViewContext

LayoutComponent.java

@ViewComponent
public class LayoutComponent {

  private final List<Page> pageList;

  public LayoutComponent(List<Page> pageList) {
    this.pageList = pageList;
  }

  public ViewContext render(ViewContext content) {
    List<NavigationItem> navigationItemList = pageList.stream()
        .map(Page::navigationItem).toList();
    return new LayoutContext(content, navigationItemList);
  }
  
  public record LayoutContext(ViewContext content, List<NavigationItem> navigationItemList) implements ViewContext {

  }
}

In the LayoutComponent.jte template we can now show a link for each page defined in the Spring ApplicationContext. Replace the <nav> element with the following.

LayoutComponent.jte

<nav>
    <h2>
        Easy Spring Auth
    </h2>
    @for(var nav: layoutContext.navigationItemList())
        <a href="${nav.URI()}">${nav.displayName()}</a>
    @endfor
    <hr>
</nav>

We can now navigate to localhost:8080 and see that the navigation works again!

Lab-4 Checkpoint 2

If you are stuck you can resume at this checkpoint with:

git checkout tags/lab-4-checkpoint-2 -b lab-4-c2

Now we need to add the GroupManagementComponent page back to our navigation.

We delete the GroupMangament.jte template and change the GroupManagementComponent.java :

GroupManagementComponent.java

@Component
public class GroupManagementComponent implements Page {

  @Override
  public NavigationItem navigationItem() {
    return new NavigationItem("Group Management", GroupController.GROUP_MANAGEMENT);
  }
}

And now the GroupManagementComponent is back!

The nice thing is that the navigation bar doesn't know that Page exists. If we change the URL of any page it all still works.

But what if we want to show the GroupManagementComponent as the first element? Well, we can use a native Spring Framework Annotation!

With the @Order annotation we can define where the navigation element is shown:

GroupManagementComponent.java

@Component
@Order(1)
public class GroupManagementComponent implements Page {

  @Override
  public NavigationItem navigationItem() {
    return new NavigationItem("Group Management", GroupController.GROUP_MANAGEMENT);
  }
}

Group Management is now the first Navigation Item!

Lab-4 Checkpoint 3

If you are stuck you can resume at this checkpoint with:

git checkout tags/lab-4-checkpoint-3 -b lab-4-c3

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