judo-runtimedependency-injection

name: judo-runtime:dependency-injection description: Guide to understanding and extending JUDO Guice dependency injection bindings. Learn about the Provider pattern, configuration qualifiers, adding custom bindings, and overriding defaults. Use when customizing JUDO runtime behavior or integrating custom components. metadata: author: BlackBelt Technology version: "${project.version}"

JUDO Dependency Injection

Guide to understanding and extending the JUDO Guice dependency injection system.

Overview

JUDO uses Google Guice for dependency injection with a layered architecture:

1. Provider Classes: Create complex objects with injected dependencies
2. Configuration Qualifiers: Type-safe configuration injection
3. Optional Overrides: Replace default implementations
4. Multibinders: Extend functionality with multiple implementations

DI Architecture

graph TB
    subgraph "Configuration Layer"
        JDMC[JudoDefaultModuleConfiguration]
        Qual[Configuration Qualifiers]
    end
    
    subgraph "Module Layer"
        JDM[JudoDefaultModule]
        Custom[Custom Modules]
    end
    
    subgraph "Provider Layer"
        DAOProv[RdbmsDAOProvider]
        DispProv[DefaultDispatcherProvider]
        OtherProv[...other providers]
    end
    
    subgraph "Service Layer"
        DAO[DAO]
        Dispatcher[Dispatcher]
        Context[Context]
        Security[AccessManager]
    end
    
    JDMC --> JDM
    Qual --> JDM
    JDM --> DAOProv
    JDM --> DispProv
    JDM --> OtherProv
    Custom --> JDM
    
    DAOProv --> DAO
    DispProv --> Dispatcher
    OtherProv --> Context
    OtherProv --> Security

Provider Pattern

JUDO uses the Provider pattern extensively. Each major component has a corresponding Provider class.

Provider Class Structure

@SuppressWarnings("rawtypes")
public class RdbmsDAOProvider implements Provider<DAO> {
    
    // Dependencies are injected by Guice
    @Inject
    private AsmModel asmModel;
    
    @Inject
    private DataSource dataSource;
    
    @Inject
    private IdentifierProvider identifierProvider;
    
    // Optional configuration with qualifiers
    @Inject(optional = true)
    @JudoConfigurationQualifiers.RdbmsDaoOptimisticLockEnabled
    @Nullable
    private Boolean optimisticLockEnabled = true;
    
    @Override
    public DAO get() {
        return RdbmsDAOImpl.builder()
            .dataSource(dataSource)
            .asmModel(asmModel)
            .identifierProvider(identifierProvider)
            .optimisticLockEnabled(optimisticLockEnabled)
            .build();
    }
}

Available Providers

Configuration Qualifiers

JUDO uses custom annotations for type-safe configuration injection.

Available Qualifiers

// In JudoConfigurationQualifiers class
@JudoConfigurationQualifiers.RdbmsDaoOptimisticLockEnabled
@JudoConfigurationQualifiers.RdbmsDaoChunkSize
@JudoConfigurationQualifiers.RdbmsDaoMaximumRecursionCount
@JudoConfigurationQualifiers.DispatcherMetricsReturned
@JudoConfigurationQualifiers.DispatcherEnableDefaultValidation
@JudoConfigurationQualifiers.DispatcherTrimString
@JudoConfigurationQualifiers.DispatcherCaseInsensitiveLike
@JudoConfigurationQualifiers.IdentifierSignerSecret
@JudoConfigurationQualifiers.MetricsCollectorEnabled
@JudoConfigurationQualifiers.MetricsCollectorVerbose
@JudoConfigurationQualifiers.MetricsCollectorConsumer
@JudoConfigurationQualifiers.PayloadValidatorRequiredStringValidatorOption
@JudoConfigurationQualifiers.ThreadContextDebugThreadFork
@JudoConfigurationQualifiers.ThreadContextInheritableContext
@JudoConfigurationQualifiers.RdbmsSequenceStart
@JudoConfigurationQualifiers.RdbmsSequenceIncrement
@JudoConfigurationQualifiers.RdbmsSequenceCreateIfNotExists
@JudoConfigurationQualifiers.QueryFactoryCustomJoinDefinitions
@JudoConfigurationQualifiers.ActorResolverCheckMappedActors

Using Qualifiers in Custom Code

public class MyCustomService {
    
    @Inject
    @JudoConfigurationQualifiers.DispatcherEnableDefaultValidation
    private Boolean enableValidation;
    
    @Inject
    @JudoConfigurationQualifiers.RdbmsDaoChunkSize
    private Integer chunkSize;
    
    // Use the injected configuration
}

Overriding Default Bindings

Method 1: Via Configuration Builder

Pass your own instance directly:

// Create custom implementation
MyCustomDAO customDao = new MyCustomDAO();

// Pass to configuration
JudoDefaultModule module = JudoDefaultModule.builder()
    .judoModelLoader(models)
    .dao(customDao)  // Override default DAO
    .build();

Method 2: Via Custom Module (Higher Priority)

Create a module that installs after JudoDefaultModule:

public class MyOverrideModule extends AbstractModule {
    
    @Override
    protected void configure() {
        // Override with custom implementation
        bind(AccessManager.class).to(MyCustomAccessManager.class);
    }
    
    @Provides
    @Singleton
    public IdentifierProvider provideIdentifierProvider() {
        return new MySequentialIdentifierProvider();
    }
}

// Install after JudoDefaultModule
Injector injector = Guice.createInjector(
    judoModule,
    new MyOverrideModule()  // Later modules override earlier
);

Method 3: Create Custom Provider

public class MyCustomDAOProvider implements Provider<DAO> {
    
    @Inject
    private AsmModel asmModel;
    
    @Inject
    private DataSource dataSource;
    
    @Override
    public DAO get() {
        return new MyCustomDAOImpl(asmModel, dataSource);
    }
}

// Register in module
public class MyModule extends AbstractModule {
    @Override
    protected void configure() {
        bind(DAO.class).toProvider(MyCustomDAOProvider.class).in(Singleton.class);
    }
}

Adding Custom Bindings

Using Multibinder for Extensions

public class InterceptorModule extends AbstractModule {
    
    @Override
    protected void configure() {
        // Register multiple interceptors
        Multibinder<OperationCallInterceptor> interceptors = 
            Multibinder.newSetBinder(binder(), OperationCallInterceptor.class);
        
        interceptors.addBinding().to(AuditLogInterceptor.class);
        interceptors.addBinding().to(WebhookInterceptor.class);
        interceptors.addBinding().to(CacheInvalidationInterceptor.class);
    }
}

Custom Services

public class MyServicesModule extends AbstractModule {
    
    @Override
    protected void configure() {
        // Simple binding
        bind(EmailService.class).to(SmtpEmailService.class);
        
        // Singleton binding
        bind(CacheService.class).to(RedisCacheService.class).in(Singleton.class);
        
        // Named binding
        bind(String.class)
            .annotatedWith(Names.named("app.name"))
            .toInstance("MyApplication");
    }
    
    @Provides
    @Singleton
    public HttpClient provideHttpClient() {
        return HttpClient.newBuilder()
            .connectTimeout(Duration.ofSeconds(10))
            .build();
    }
}

Binding Lifecycle

sequenceDiagram
    participant App as Application
    participant Guice
    participant JDM as JudoDefaultModule
    participant Provider
    participant Service
    
    App->>Guice: createInjector(modules)
    Guice->>JDM: configure()
    JDM->>Guice: bind(Service).toProvider(Provider)
    
    Note over Guice: Injector created
    
    App->>Guice: getInstance(Service)
    Guice->>Provider: get()
    Provider->>Guice: Request dependencies
    Guice-->>Provider: Inject dependencies
    Provider->>Service: Create instance
    Provider-->>Guice: Return service
    Guice-->>App: Return service

Conditional Binding

Optional Dependencies

public class MyProvider implements Provider<MyService> {
    
    // Optional injection - null if not bound
    @Inject(optional = true)
    @Nullable
    private ExternalService externalService;
    
    @Override
    public MyService get() {
        if (externalService != null) {
            return new MyServiceWithExternal(externalService);
        }
        return new MyServiceStandalone();
    }
}

Environment-Based Configuration

public class EnvironmentModule extends AbstractModule {
    
    private final String environment;
    
    public EnvironmentModule(String environment) {
        this.environment = environment;
    }
    
    @Override
    protected void configure() {
        if ("production".equals(environment)) {
            bind(DataSource.class).toProvider(ProductionDataSourceProvider.class);
        } else {
            bind(DataSource.class).toProvider(DevelopmentDataSourceProvider.class);
        }
    }
}

Testing with DI

Mocking Dependencies

public class MyServiceTest {
    
    @Test
    void testWithMocks() {
        // Create mocks
        DAO mockDao = mock(DAO.class);
        AccessManager mockAccessManager = mock(AccessManager.class);
        
        // Create injector with overrides
        Injector injector = Guice.createInjector(
            judoModule,
            new AbstractModule() {
                @Override
                protected void configure() {
                    bind(DAO.class).toInstance(mockDao);
                    bind(AccessManager.class).toInstance(mockAccessManager);
                }
            }
        );
        
        // Get service with mocked dependencies
        MyService service = injector.getInstance(MyService.class);
        
        // Test
        when(mockDao.find(any())).thenReturn(testPayload);
        service.doSomething();
        verify(mockDao).find(any());
    }
}

Using JUDO TestKit

@JudoTest
class IntegrationTest {
    
    @Inject
    Dispatcher dispatcher;
    
    @Inject
    DAO dao;
    
    @Test
    void testOperation() {
        // Dependencies automatically injected by TestKit
        var result = dispatcher.call("MyEntity", "myOperation", payload);
        assertThat(result).isNotNull();
    }
}

Common Patterns

Decorator Pattern

public class LoggingDAODecorator implements DAO {
    
    private final DAO delegate;
    private final Logger log;
    
    public LoggingDAODecorator(DAO delegate) {
        this.delegate = delegate;
        this.log = LoggerFactory.getLogger(LoggingDAODecorator.class);
    }
    
    @Override
    public Payload create(String type, Payload payload) {
        log.info("Creating {} with {}", type, payload);
        Payload result = delegate.create(type, payload);
        log.info("Created: {}", result);
        return result;
    }
    // ... delegate other methods
}

// Bind decorator
bind(DAO.class).toProvider(() -> {
    DAO baseDao = baseProvider.get();
    return new LoggingDAODecorator(baseDao);
});

Factory Pattern

public interface ServiceFactory {
    MyService create(String tenantId);
}

public class ServiceFactoryImpl implements ServiceFactory {
    
    @Inject
    private Provider<DAO> daoProvider;
    
    @Override
    public MyService create(String tenantId) {
        return new MyService(daoProvider.get(), tenantId);
    }
}

// Bind factory
bind(ServiceFactory.class).to(ServiceFactoryImpl.class);

See Also

• judo-runtime:module-setup - Module configuration guide
• judo-runtime:create-interceptor - Creating operation interceptors
• judo-runtime-core-guice-testkit - Testing utilities
• Google Guice documentation: https://github.com/google/guice