Package org.elasticsearch.common.inject

Interface Binder

  • All Known Subinterfaces:
    PrivateBinder
    public interface Binder
    Collects configuration information (primarily bindings) which will be used to create an Injector. Guice provides this object to your application's Module implementors so they may each contribute their own bindings and other registrations.

    The Guice Binding EDSL

    Guice uses an embedded domain-specific language, or EDSL, to help you create bindings simply and readably. This approach is great for overall usability, but it does come with a small cost: it is difficult to learn how to use the Binding EDSL by reading method-level javadocs. Instead, you should consult the series of examples below. To save space, these examples omit the opening binder, just as you will if your module extends AbstractModule. 

         bind(ServiceImpl.class);
    This statement does essentially nothing; it "binds the ServiceImpl class to itself" and does not change Guice's default behavior. You may still want to use this if you prefer your Module class to serve as an explicit manifest for the services it provides. Also, in rare cases, Guice may be unable to validate a binding at injector creation time unless it is given explicitly. 
         bind(Service.class).to(ServiceImpl.class);
    Specifies that a request for a Service instance with no binding annotations should be treated as if it were a request for a ServiceImpl instance. This overrides the function of any @ImplementedBy or @ProvidedBy annotations found on Service, since Guice will have already "moved on" to ServiceImpl before it reaches the point when it starts looking for these annotations. 
         bind(Service.class).toProvider(ServiceProvider.class);
    In this example, ServiceProvider must extend or implement Provider<Service>. This binding specifies that Guice should resolve an unannotated injection request for Service by first resolving an instance of ServiceProvider in the regular way, then calling get() on the resulting Provider instance to obtain the Service instance.

    The Provider you use here does not have to be a "factory"; that is, a provider which always creates each instance it provides. However, this is generally a good practice to follow. You can then use Guice's concept of scopes to guide when creation should happen -- "letting Guice work for you". 

         bind(Service.class).annotatedWith(Red.class).to(ServiceImpl.class);
    Like the previous example, but only applies to injection requests that use the binding annotation @Red. If your module also includes bindings for particular values of the @Red annotation (see below), then this binding will serve as a "catch-all" for any values of @Red that have no exact match in the bindings. 
         bind(ServiceImpl.class).in(Singleton.class);
     // or, alternatively
     bind(ServiceImpl.class).in(Scopes.SINGLETON);
    Either of these statements places the ServiceImpl class into singleton scope. Guice will create only one instance of ServiceImpl and will reuse it for all injection requests of this type. Note that it is still possible to bind another instance of ServiceImpl if the second binding is qualified by an annotation as in the previous example. Guice is not overly concerned with preventing you from creating multiple instances of your "singletons", only with enabling your application to share only one instance if that's all you tell Guice you need.

    Note: a scope specified in this way overrides any scope that was specified with an annotation on the ServiceImpl class.

    Besides Singleton/Scopes.SINGLETON, there are servlet-specific scopes available in com.google.inject.servlet.ServletScopes, and your Modules can contribute their own custom scopes for use here as well. 

         bind(new TypeLiteral<PaymentService<CreditCard>>() {})
         .to(CreditCardPaymentService.class);
    This admittedly odd construct is the way to bind a parameterized type. It tells Guice how to honor an injection request for an element of type PaymentService<CreditCard>. The class CreditCardPaymentService must implement the PaymentService<CreditCard> interface. Guice cannot currently bind or inject a generic type, such as Set<E>; all type parameters must be fully specified. 
         bind(Service.class).toInstance(new ServiceImpl());
     // or, alternatively
     bind(Service.class).toInstance(SomeLegacyRegistry.getService());
    In this example, your module itself, not Guice, takes responsibility for obtaining a ServiceImpl instance, then asks Guice to always use this single instance to fulfill all Service injection requests. When the Injector is created, it will automatically perform field and method injection for this instance, but any injectable constructor on ServiceImpl is simply ignored. Note that using this approach results in "eager loading" behavior that you can't control. 
         bindConstant().annotatedWith(ServerHost.class).to(args[0]);
    Sets up a constant binding. Constant injections must always be annotated. When a constant binding's value is a string, it is eligible for conversion to all primitive types, to all enums, and to class literals. Conversions for other types can be configured using convertToTypes(). 
       @Color("red") Color red; // A member variable (field)
    . . .
     red = MyModule.class.getDeclaredField("red").getAnnotation(Color.class);
     bind(Service.class).annotatedWith(red).to(RedService.class);
    If your binding annotation has parameters you can apply different bindings to different specific values of your annotation. Getting your hands on the right instance of the annotation is a bit of a pain -- one approach, shown above, is to apply a prototype annotation to a field in your module class, so that you can read this annotation instance and give it to Guice. 
         bind(Service.class)
         .annotatedWith(Names.named("blue"))
         .to(BlueService.class);
    Differentiating by names is a common enough use case that we provided a standard annotation, @Named. Because of Guice's library support, binding by name is quite easier than in the arbitrary binding annotation case we just saw. However, remember that these names will live in a single flat namespace with all the other names used in your application.

    The above list of examples is far from exhaustive. If you can think of how the concepts of one example might coexist with the concepts from another, you can most likely weave the two together. If the two concepts make no sense with each other, you most likely won't be able to do it. In a few cases Guice will let something bogus slip by, and will then inform you of the problems at runtime, as soon as you try to create your Injector.

    The other methods of Binder such as bindScope(java.lang.Class<? extends java.lang.annotation.Annotation>, org.elasticsearch.common.inject.Scope), install(org.elasticsearch.common.inject.Module), requestStaticInjection(java.lang.Class<?>...), addError(java.lang.String, java.lang.Object...) and currentStage() are not part of the Binding EDSL; you can learn how to use these in the usual way, from the method documentation.

    • Method Detail

      • bindScope

        void bindScope​(java.lang.Class<? extends java.lang.annotation.Annotation> annotationType,
               Scope scope)
        Binds a scope to an annotation.

      • requestInjection

        <T> void requestInjection​(TypeLiteral<T> type,
                          T instance)
        Upon successful creation, the Injector will inject instance fields and methods of the given object.
        Parameters:
        type - of instance
        instance - for which members will be injected
        Since:
        2.0

      • requestInjection

        void requestInjection​(java.lang.Object instance)
        Upon successful creation, the Injector will inject instance fields and methods of the given object.
        Parameters:
        instance - for which members will be injected
        Since:
        2.0

      • requestStaticInjection

        void requestStaticInjection​(java.lang.Class<?>... types)
        Upon successful creation, the Injector will inject static fields and methods in the given classes.
        Parameters:
        types - for which static members will be injected

      • install

        void install​(Module module)
        Uses the given module to configure more bindings.

      • currentStage

        Stage currentStage()
        Gets the current stage.

      • addError

        void addError​(java.lang.String message,
              java.lang.Object... arguments)
        Records an error message which will be presented to the user at a later time. Unlike throwing an exception, this enable us to continue configuring the Injector and discover more errors. Uses String.format(String, Object[]) to insert the arguments into the message.

      • addError

        void addError​(java.lang.Throwable t)
        Records an exception, the full details of which will be logged, and the message of which will be presented to the user at a later time. If your Module calls something that you worry may fail, you should catch the exception and pass it into this.

      • addError

        void addError​(Message message)
        Records an error message to be presented to the user at a later time.
        Since:
        2.0

      • getProvider

        <T> Provider<T> getProvider​(Key<T> key)
        Returns the provider used to obtain instances for the given injection key. The returned will not be valid until the Injector has been created. The provider will throw an IllegalStateException if you try to use it beforehand.
        Since:
        2.0

      • getProvider

        <T> Provider<T> getProvider​(java.lang.Class<T> type)
        Returns the provider used to obtain instances for the given injection type. The returned provider will not be valid until the Injector has been created. The provider will throw an IllegalStateException if you try to use it beforehand.
        Since:
        2.0

      • getMembersInjector

        <T> MembersInjector<T> getMembersInjector​(TypeLiteral<T> typeLiteral)
        Returns the members injector used to inject dependencies into methods and fields on instances of the given type T. The returned members injector will not be valid until the main Injector has been created. The members injector will throw an IllegalStateException if you try to use it beforehand.
        Parameters:
        typeLiteral - type to get members injector for
        Since:
        2.0

      • getMembersInjector

        <T> MembersInjector<T> getMembersInjector​(java.lang.Class<T> type)
        Returns the members injector used to inject dependencies into methods and fields on instances of the given type T. The returned members injector will not be valid until the main Injector has been created. The members injector will throw an IllegalStateException if you try to use it beforehand.
        Parameters:
        type - type to get members injector for
        Since:
        2.0

      • convertToTypes

        void convertToTypes​(Matcher<? super TypeLiteral<?>> typeMatcher,
                    TypeConverter converter)
        Binds a type converter. The injector will use the given converter to convert string constants to matching types as needed.
        Parameters:
        typeMatcher - matches types the converter can handle
        converter - converts values
        Since:
        2.0

      • bindListener

        void bindListener​(Matcher<? super TypeLiteral<?>> typeMatcher,
                  TypeListener listener)
        Registers a listener for injectable types. Guice will notify the listener when it encounters injectable types matched by the given type matcher.
        Parameters:
        typeMatcher - that matches injectable types the listener should be notified of
        listener - for injectable types matched by typeMatcher
        Since:
        2.0

      • withSource

        Binder withSource​(java.lang.Object source)
        Returns a binder that uses source as the reference location for configuration errors. This is typically a StackTraceElement for .java source but it could any binding source, such as the path to a .properties file.
        Parameters:
        source - any object representing the source location and has a concise toString() value
        Returns:
        a binder that shares its configuration with this binder
        Since:
        2.0

      • skipSources

        Binder skipSources​(java.lang.Class<?>... classesToSkip)
        Returns a binder that skips classesToSkip when identify the calling code. The caller's StackTraceElement is used to locate the source of configuration errors.
        Parameters:
        classesToSkip - library classes that create bindings on behalf of their clients.
        Returns:
        a binder that shares its configuration with this binder.
        Since:
        2.0

      • newPrivateBinder

        PrivateBinder newPrivateBinder()
        Creates a new private child environment for bindings and other configuration. The returned binder can be used to add and configuration information in this environment. See PrivateModule for details.
        Returns:
        a binder that inherits configuration from this binder. Only exposed configuration on the returned binder will be visible to this binder.
        Since:
        2.0