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The EmbeddedExtension interface represents a programmatically-defined HiveMQ extension that can be added to an embedded HiveMQ instance.

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Package

com.hivemq.embedded.EmbeddedExtension

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Interface Declaration

public interface EmbeddedExtension
Since: CE 2020.5

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Methods

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builder()

Creates a new EmbeddedExtensionBuilder instance. 
static @NotNull EmbeddedExtensionBuilder builder()
Returns:
  • EmbeddedExtensionBuilder - A new builder instance for creating an EmbeddedExtension
Example: 
EmbeddedExtensionBuilder builder = EmbeddedExtension.builder();

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getId()

Returns the unique identifier of the extension. 
@NotNull String getId()
Returns:
  • String - The unique ID of the extension
Example: 
EmbeddedExtension extension = EmbeddedExtension.builder()
    .withId("my-extension")
    .withName("My Extension")
    .withVersion("1.0.0")
    .withExtensionMain(new MyExtensionMain())
    .build();

String id = extension.getId(); // "my-extension"

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getName()

Returns the human-readable name of the extension. 
@NotNull String getName()
Returns:
  • String - The name of the extension
Example: 
String name = extension.getName(); // "My Extension"

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getVersion()

Returns the version of the extension. 
@NotNull String getVersion()
Returns:
  • String - The version of the extension
Example: 
String version = extension.getVersion(); // "1.0.0"

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getAuthor()

Returns the author of the extension. 
@Nullable String getAuthor()
Returns:
  • String - The author of the extension, or null if not provided
Example: 
String author = extension.getAuthor(); // "HiveMQ" or null

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getPriority()

Returns the extension’s execution priority. 
int getPriority()
Returns:
  • int - The priority value. Extensions are called in order from highest to lowest priority.
Behavior:
  • All extensions are called in the order of their priority (highest to lowest).
  • Default value: 0
Example: 
int priority = extension.getPriority(); // 0

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getStartPriority()

Returns the extension’s start priority. 
int getStartPriority()
Returns:
  • int - The start priority value. Extensions are started in order from highest to lowest priority.
Behavior:
  • All extensions are started in the order of their start priority (highest to lowest).
  • Default value: 1000
Example: 
int startPriority = extension.getStartPriority(); // 1000

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getExtensionMain()

Returns the extension’s main class instance. 
@NotNull ExtensionMain getExtensionMain()
Returns:
  • ExtensionMain - The extension main class that implements extensionStart() and extensionStop()
Example: 
ExtensionMain main = extension.getExtensionMain();

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Usage Examples

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Basic Extension

import com.hivemq.embedded.EmbeddedExtension;
import com.hivemq.extension.sdk.api.ExtensionMain;
import com.hivemq.extension.sdk.api.parameter.ExtensionStartInput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStartOutput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStopInput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStopOutput;
import org.jetbrains.annotations.NotNull;

public class BasicExtensionExample {
    public static void main(String[] args) {
        EmbeddedExtension extension = EmbeddedExtension.builder()
            .withId("basic-extension")
            .withName("Basic Extension")
            .withVersion("1.0.0")
            .withExtensionMain(new BasicExtensionMain())
            .build();
        
        // Access extension properties
        System.out.println("ID: " + extension.getId());
        System.out.println("Name: " + extension.getName());
        System.out.println("Version: " + extension.getVersion());
    }
    
    private static class BasicExtensionMain implements ExtensionMain {
        @Override
        public void extensionStart(
                @NotNull ExtensionStartInput input,
                @NotNull ExtensionStartOutput output) {
            System.out.println("Extension started");
        }
        
        @Override
        public void extensionStop(
                @NotNull ExtensionStopInput input,
                @NotNull ExtensionStopOutput output) {
            System.out.println("Extension stopped");
        }
    }
}

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Extension with Priorities

import com.hivemq.embedded.EmbeddedExtension;
import com.hivemq.extension.sdk.api.ExtensionMain;
import com.hivemq.extension.sdk.api.parameter.ExtensionStartInput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStartOutput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStopInput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStopOutput;
import org.jetbrains.annotations.NotNull;

public class PriorityExtensionExample {
    public static void main(String[] args) {
        EmbeddedExtension highPriorityExtension = EmbeddedExtension.builder()
            .withId("high-priority-ext")
            .withName("High Priority Extension")
            .withVersion("1.0.0")
            .withPriority(100)          // Runs first
            .withStartPriority(2000)     // Starts first
            .withAuthor("HiveMQ")
            .withExtensionMain(new MyExtensionMain())
            .build();
        
        System.out.println("Priority: " + highPriorityExtension.getPriority());
        System.out.println("Start Priority: " + highPriorityExtension.getStartPriority());
    }
    
    private static class MyExtensionMain implements ExtensionMain {
        @Override
        public void extensionStart(
                @NotNull ExtensionStartInput input,
                @NotNull ExtensionStartOutput output) {
            System.out.println("High priority extension started");
        }
        
        @Override
        public void extensionStop(
                @NotNull ExtensionStopInput input,
                @NotNull ExtensionStopOutput output) {
            System.out.println("High priority extension stopped");
        }
    }
}

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Complete Extension with HiveMQ

import com.hivemq.embedded.EmbeddedExtension;
import com.hivemq.embedded.EmbeddedHiveMQ;
import com.hivemq.extension.sdk.api.ExtensionMain;
import com.hivemq.extension.sdk.api.parameter.ExtensionStartInput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStartOutput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStopInput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStopOutput;
import com.hivemq.extension.sdk.api.services.Services;
import org.jetbrains.annotations.NotNull;

public class CompleteExample {
    public static void main(String[] args) {
        EmbeddedExtension extension = EmbeddedExtension.builder()
            .withId("logging-extension")
            .withName("Connection Logging Extension")
            .withVersion("1.0.0")
            .withPriority(0)
            .withStartPriority(1000)
            .withAuthor("Your Company")
            .withExtensionMain(new LoggingExtensionMain())
            .build();
        
        try (EmbeddedHiveMQ hivemq = EmbeddedHiveMQ.builder()
                .withEmbeddedExtension(extension)
                .build()) {
            
            hivemq.start().join();
            System.out.println("HiveMQ running with extension: " + extension.getName());
            
            Thread.sleep(60000); // Run for 1 minute
            
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    private static class LoggingExtensionMain implements ExtensionMain {
        @Override
        public void extensionStart(
                @NotNull ExtensionStartInput input,
                @NotNull ExtensionStartOutput output) {
            
            // Register client lifecycle callbacks
            Services.eventRegistry().setClientLifecycleEventListener(
                eventListenerInput -> {
                    eventListenerInput.getClientEventListeners()
                        .addConnectEventListener(context -> {
                            System.out.println("Client connected: " + 
                                context.getClientInformation().getClientId());
                        })
                        .addDisconnectEventListener(context -> {
                            System.out.println("Client disconnected: " + 
                                context.getClientInformation().getClientId());
                        });
                });
            
            System.out.println("Logging extension started successfully");
        }
        
        @Override
        public void extensionStop(
                @NotNull ExtensionStopInput input,
                @NotNull ExtensionStopOutput output) {
            System.out.println("Logging extension stopped");
        }
    }
}

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Accessing Extension Information

import com.hivemq.embedded.EmbeddedExtension;
import com.hivemq.extension.sdk.api.ExtensionMain;
import com.hivemq.extension.sdk.api.parameter.ExtensionStartInput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStartOutput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStopInput;
import com.hivemq.extension.sdk.api.parameter.ExtensionStopOutput;
import org.jetbrains.annotations.NotNull;

public class ExtensionInfoExample {
    public static void main(String[] args) {
        EmbeddedExtension extension = EmbeddedExtension.builder()
            .withId("info-extension")
            .withName("Information Extension")
            .withVersion("2.1.0")
            .withAuthor("John Doe")
            .withPriority(50)
            .withStartPriority(1500)
            .withExtensionMain(new InfoExtensionMain())
            .build();
        
        printExtensionInfo(extension);
    }
    
    private static void printExtensionInfo(EmbeddedExtension extension) {
        System.out.println("===== Extension Information =====");
        System.out.println("ID: " + extension.getId());
        System.out.println("Name: " + extension.getName());
        System.out.println("Version: " + extension.getVersion());
        System.out.println("Author: " + extension.getAuthor());
        System.out.println("Priority: " + extension.getPriority());
        System.out.println("Start Priority: " + extension.getStartPriority());
        System.out.println("=================================");
    }
    
    private static class InfoExtensionMain implements ExtensionMain {
        @Override
        public void extensionStart(
                @NotNull ExtensionStartInput input,
                @NotNull ExtensionStartOutput output) {
            // Extension logic here
        }
        
        @Override
        public void extensionStop(
                @NotNull ExtensionStopInput input,
                @NotNull ExtensionStopOutput output) {
            // Cleanup logic here
        }
    }
}

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See Also