com.google.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 eligile 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. 
         Constructor loneCtor = getLoneCtorFromServiceImplViaReflection();
     bind(ServiceImpl.class)
         .toConstructor(loneCtor);
    In this example, we directly tell Guice which constructor to use in a concrete class implementation. It means that we do not need to place @Inject on any of the constructors and that Guice treats the provided constructor as though it were annotated so. It is useful for cases where you cannot modify existing classes and is a bit simpler than using a Provider.

    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>, com.google.inject.Scope), bindInterceptor(com.google.inject.matcher.Matcher<? super java.lang.Class<?>>, com.google.inject.matcher.Matcher<? super java.lang.reflect.Method>, org.aopalliance.intercept.MethodInterceptor...), install(com.google.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.

    Author:
    crazybob@google.com (Bob Lee), jessewilson@google.com (Jesse Wilson), kevinb@google.com (Kevin Bourrillion)

    • Method Detail

      • bindInterceptor

        void bindInterceptor(Matcher<? super Class<?>> classMatcher,
                   Matcher<? super Method> methodMatcher,
                   org.aopalliance.intercept.MethodInterceptor... interceptors)
        Binds method interceptor[s] to methods matched by class and method matchers. A method is eligible for interception if:
        • Guice created the instance the method is on
        • Neither the enclosing type nor the method is final
        • And the method is package-private, protected, or public
        Parameters:
        classMatcher - matches classes the interceptor should apply to. For example: only(Runnable.class).
        methodMatcher - matches methods the interceptor should apply to. For example: annotatedWith(Transactional.class).
        interceptors - to bind. The interceptors are called in the order they are given.

      • bindScope

        void bindScope(Class<? extends 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(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(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(String message,
            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(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 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

      • getProvider

        <T> Provider<T> getProvider(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(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(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(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

      • requireExplicitBindings

        void requireExplicitBindings()
        Instructs the Injector that bindings must be listed in a Module in order to be injected. Classes that are not explicitly bound in a module cannot be injected. Bindings created through a linked binding ( bind(Foo.class).to(FooImpl.class)) are allowed, but the implicit binding (FooImpl) cannot be directly injected unless it is also explicitly bound (bind(FooImpl.class)).

        Tools can still retrieve bindings for implicit bindings (bindings created through a linked binding) if explicit bindings are required, however Binding.getProvider() will fail.

        By default, explicit bindings are not required.

        If a parent injector requires explicit bindings, then all child injectors (and private modules within that injector) also require explicit bindings. If a parent does not require explicit bindings, a child injector or private module may optionally declare itself as requiring explicit bindings. If it does, the behavior is limited only to that child or any grandchildren. No siblings of the child will require explicit bindings.

        If the parent did not require explicit bindings but the child does, it is possible that a linked binding in the child may add a JIT binding to the parent. The child will not be allowed to reference the target binding directly, but the parent and other children of the parent may be able to.

        Since:
        3.0

      • disableCircularProxies

        void disableCircularProxies()
        Prevents Guice from constructing a Proxy when a circular dependency is found. By default, circular proxies are not disabled.

        If a parent injector disables circular proxies, then all child injectors (and private modules within that injector) also disable circular proxies. If a parent does not disable circular proxies, a child injector or private module may optionally declare itself as disabling circular proxies. If it does, the behavior is limited only to that child or any grandchildren. No siblings of the child will disable circular proxies.

        Since:
        3.0

      • requireAtInjectOnConstructors

        void requireAtInjectOnConstructors()
        Requires that a @Inject annotation exists on a constructor in order for Guice to consider it an eligible injectable class. By default, Guice will inject classes that have a no-args constructor if no @Inject annotation exists on any constructor.

        If the class is bound using LinkedBindingBuilder.toConstructor(java.lang.reflect.Constructor<S>), Guice will still inject that constructor regardless of annotations.

        Since:
        4.0

      • requireExactBindingAnnotations

        void requireExactBindingAnnotations()
        Requires that Guice finds an exactly matching binding annotation. This disables the error-prone feature in Guice where it can substitute a binding for @Named Foo when attempting to inject @Named("foo") Foo.
        Since:
        4.0

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