Portlet Advance

1. Portlet Core Architecture

Portlet Container & OSGi Integration

graph TB
    subgraph OSGi Runtime
        A[Portlet Container] --> B[Portlet 1]
        A --> C[Portlet 2]
        A --> D[...]
    end
    E[HTTP Requests] --> A
    A --> F[Portal Page]

Key Components:

• Portlet Container: Manages lifecycle (init, render, destroy)
• OSGi Service Registry: Enables dependency injection
• Portlet Bridge: Connects portlets to Liferay’s rendering engine

Portlet Class Hierarchy

classDiagram
    GenericPortlet <|-- MVCPortlet
    GenericPortlet <|-- BaseJSPServlet
    GenericPortlet : +doView()
    GenericPortlet : +doEdit()
    GenericPortlet : +doConfig()
    MVCPortlet : +render()
    MVCPortlet : +processAction()

2. Advanced Portlet Modes

Custom Portlet Modes

@PortletConfiguration(
    portletName = "myPortlet",
    modes = {
        @PortletMode(name = "print", markup = "text/html"),
        @PortletMode(name = "dashboard")
    }
)
public class MyPortlet extends GenericPortlet {
    @Override
    protected void doPrint(RenderRequest request, RenderResponse response) {
        // Print-specific rendering
    }
}

Mode Transition Flow

stateDiagram-v2
    [*] --> VIEW
    VIEW --> EDIT: User clicks edit
    EDIT --> CONFIG: Admin clicks config
    CONFIG --> VIEW: Settings saved
    VIEW --> PRINT: Print button
    PRINT --> VIEW: Print complete

3. Inter-Portlet Communication (IPC)

Event-Based IPC

// Sender Portlet
@ProcessAction(name = "sendData")
public void sendData(ActionRequest request, ActionResponse response) {
    response.setEvent("user/data", userData);
}

// Receiver Portlet
@ProcessEvent(qname = "{http://example.com}user/data")
public void receiveData(EventRequest request, EventResponse response) {
    UserData data = (UserData)request.getEvent();
}

Public Render Parameters

portlet.xml

<portlet>
    <supported-public-render-parameter>user_id</supported-public-render-parameter>
</portlet>

<!-- liferay-portlet.xml -->
<portlet>
    <public-render-parameter>
        <identifier>user_id</identifier>
        <qname>[http://example.com]user_id</qname>
    </public-render-parameter>
</portlet>

4. Advanced Configuration

Portlet Preferences (Database-Persisted)

@PortletConfiguration(
    portletName = "configurablePortlet",
    preferences = {
        @PortletPreference(
            name = "colorScheme",
            value = "{\"default\":\"blue\",\"options\":[\"red\",\"green\"]}"
        )
    }
)
public class ConfigurablePortlet extends GenericPortlet {
    // ...
}

Dynamic Preference Management

PortletPreferences prefs = request.getPreferences();
prefs.setValue("itemsPerPage", "10");
prefs.store();  // Persists to database

5. Performance Optimization

Caching Strategies

graph LR
    A[Request] --> B{Cache Valid?}
    B -->|Yes| C[Return Cached]
    B -->|No| D[Process Request]
    D --> E[Store in Cache]

Implementation:

@Header(
    name = "Cache-Control",
    value = "public, max-age=3600"  // 1 hour cache
)
public class CachedPortlet extends GenericPortlet {
    // ...
}

Resource Serving Best Practices

@ServeResource(
    resourceID = "chartData",
    contentType = "application/json"
)
public void serveChartData(ResourceRequest request, ResourceResponse response) {
    // Generate and stream JSON
}

6. Security Considerations

Permission Checking

if (PortletPermissionUtil.contains(
    permissionChecker,
    plid,
    portletId,
    ActionKeys.VIEW)) {
    // Render content
}

CSRF Protection

<portlet:actionURL var="formAction">
  <portlet:param
    name="<%=Constants.CSRF_TOKEN%>"
    value="<%=request.getAttribute(Constants.CSRF_TOKEN)%>"
  />
</portlet:actionURL>

7. Migration Considerations (6.2 → 7.4)

Key Changes

Liferay 6.2	Liferay 7.4
PortletSpec 2.0	PortletSpec 3.0
Plugin SDK	Blade CLI/Gradle
Spring Portlet MVC	OSGi DS Components
liferay-portlet.xml	OSGi Metadata

Migration Path

gantt
    title Portlet Migration Timeline
    dateFormat  YYYY-MM-DD
    section Analysis
    Code Audit       :done, a1, 2023-01-01, 14d
    Dependency Mapping :active, a2, after a1, 10d
    section Implementation
    OSGi Conversion  :a3, after a2, 21d
    Testing          :a4, after a3, 14d

8. Debugging & Troubleshooting

Common Issues

1. ClassCastException - Check OSGi service versions
2. Portlet Not Appearing - Verify bnd.bnd headers
3. Preferences Not Saving - Check permission constraints

Diagnostic Tools

# Gogo Shell Commands:
lb | grep my.portlet  # Find bundle
services | grep Portlet  # Check registrations
log:display  # View logs

9. Real-World Implementation Example

Complete Dashboard Portlet

@Component(
    property = {
        "com.liferay.portlet.display-category=category.sample",
        "com.liferay.portlet.instanceable=true",
        "javax.portlet.name=com_example_DashboardPortlet"
    },
    service = Portlet.class
)
public class DashboardPortlet extends MVCPortlet {

    @Reference
    private UserLocalService _userService;

    @Override
    public void render(RenderRequest request, RenderResponse response) {
        request.setAttribute("userCount", _userService.getUsersCount());
        super.render(request, response);
    }

    @ServeResource
    public void serveCharts(ResourceRequest request, ResourceResponse response) {
        // Return JSON data for AJAX charts
    }
}

10. Future-Proofing

Headless Portlet Patterns

@ProviderType
public interface MyPortletService {
    String getDataAsJson();
}

@Component(service = MyPortletService.class)
public class MyPortletServiceImpl implements MyPortletService {
    // ...
}

Web Components Integration

class MyPortletElement extends HTMLElement {
  connectedCallback() {
    this.innerHTML = `<h1>Portlet as Web Component</h1>`;
  }
}
customElements.define("my-portlet", MyPortletElement);

Next Steps for Mastery

1. Deep Dive into OSGi Services:

   blade create -t service my-service-api
   blade create -t service-wrapper my-service-override

2. Explore Liferay’s Frontend Toolkit:

   npm init @liferay/js-portlet@latest

3. Performance Tuning:

   • Implement Fragment Caching
   • Study Portlet Filter Chains