org.elasticsearch.common.inject.Binder Maven / Gradle / Ivy
/*
* Copyright (C) 2007 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.elasticsearch.common.inject;
import org.elasticsearch.common.inject.binder.AnnotatedBindingBuilder;
import org.elasticsearch.common.inject.binder.AnnotatedConstantBindingBuilder;
import org.elasticsearch.common.inject.binder.LinkedBindingBuilder;
import org.elasticsearch.common.inject.matcher.Matcher;
import org.elasticsearch.common.inject.spi.Message;
import org.elasticsearch.common.inject.spi.TypeConverter;
import org.elasticsearch.common.inject.spi.TypeListener;
import java.lang.annotation.Annotation;
/**
* Collects configuration information (primarily bindings) which will be
* used to create an {@link Injector}. Guice provides this object to your
* application's {@link 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
* {@code binder}, just as you will if your module extends
* {@link AbstractModule}.
*
*
* bind(ServiceImpl.class);
*
* This statement does essentially nothing; it "binds the {@code ServiceImpl}
* class to itself" and does not change Guice's default behavior. You may still
* want to use this if you prefer your {@link 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 {@code Service} instance with no binding
* annotations should be treated as if it were a request for a
* {@code ServiceImpl} instance. This overrides the function of any
* {@link ImplementedBy @ImplementedBy} or {@link ProvidedBy @ProvidedBy}
* annotations found on {@code Service}, since Guice will have already
* "moved on" to {@code ServiceImpl} before it reaches the point when it starts
* looking for these annotations.
*
*
* bind(Service.class).toProvider(ServiceProvider.class);
*
* In this example, {@code ServiceProvider} must extend or implement
* {@code Provider}. This binding specifies that Guice should resolve
* an unannotated injection request for {@code Service} by first resolving an
* instance of {@code ServiceProvider} in the regular way, then calling
* {@link Provider#get get()} on the resulting Provider instance to obtain the
* {@code Service} instance.
*
* The {@link 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 {@link Scope 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 {@code @Red}. If your module also includes bindings
* for particular values of the {@code @Red} annotation (see below),
* then this binding will serve as a "catch-all" for any values of {@code @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 {@code ServiceImpl} class into
* singleton scope. Guice will create only one instance of {@code ServiceImpl}
* and will reuse it for all injection requests of this type. Note that it is
* still possible to bind another instance of {@code 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 {@code ServiceImpl} class.
*
*
Besides {@link Singleton}/{@link Scopes#SINGLETON}, there are
* servlet-specific scopes available in
* {@code 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
* {@code PaymentService}. The class
* {@code CreditCardPaymentService} must implement the
* {@code PaymentService} interface. Guice cannot currently bind or
* inject a generic type, such as {@code Set}; 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 {@code ServiceImpl} instance, then asks Guice to always use
* this single instance to fulfill all {@code Service} injection requests. When
* the {@link Injector} is created, it will automatically perform field
* and method injection for this instance, but any injectable constructor on
* {@code 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 {@link Enum#valueOf(Class, String) all enums}, and to
* {@link Class#forName class literals}. Conversions for other types can be
* configured using {@link #convertToTypes(Matcher, TypeConverter)
* convertToTypes()}.
*
*
* {@literal @}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, {@link org.elasticsearch.common.inject.name.Named @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 {@link #bindScope},
* {@link #bindInterceptor}, {@link #install}, {@link #requestStaticInjection},
* {@link #addError} and {@link #currentStage} are not part of the Binding EDSL;
* you can learn how to use these in the usual way, from the method
* documentation.
*
* @author [email protected] (Bob Lee)
* @author [email protected] (Jesse Wilson)
* @author [email protected] (Kevin Bourrillion)
*/
public interface Binder {
/**
* Binds a scope to an annotation.
*/
void bindScope(Class annotationType, Scope scope);
/**
* See the EDSL examples at {@link Binder}.
*/
LinkedBindingBuilder bind(Key key);
/**
* See the EDSL examples at {@link Binder}.
*/
AnnotatedBindingBuilder bind(TypeLiteral typeLiteral);
/**
* See the EDSL examples at {@link Binder}.
*/
AnnotatedBindingBuilder bind(Class type);
/**
* See the EDSL examples at {@link Binder}.
*/
AnnotatedConstantBindingBuilder bindConstant();
/**
* Upon successful creation, the {@link Injector} will inject instance fields
* and methods of the given object.
*
* @param type of instance
* @param instance for which members will be injected
* @since 2.0
*/
void requestInjection(TypeLiteral type, T instance);
/**
* Upon successful creation, the {@link Injector} will inject instance fields
* and methods of the given object.
*
* @param instance for which members will be injected
* @since 2.0
*/
void requestInjection(Object instance);
/**
* Upon successful creation, the {@link Injector} will inject static fields
* and methods in the given classes.
*
* @param types for which static members will be injected
*/
void requestStaticInjection(Class... types);
/**
* Uses the given module to configure more bindings.
*/
void install(Module module);
/**
* Gets the current stage.
*/
Stage currentStage();
/**
* 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 {@link
* String#format(String, Object[])} to insert the arguments into the
* message.
*/
void addError(String message, Object... arguments);
/**
* 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.
*/
void addError(Throwable t);
/**
* Records an error message to be presented to the user at a later time.
*
* @since 2.0
*/
void addError(Message message);
/**
* Returns the provider used to obtain instances for the given injection key.
* The returned will not be valid until the {@link Injector} has been
* created. The provider will throw an {@code IllegalStateException} if you
* try to use it beforehand.
*
* @since 2.0
*/
Provider getProvider(Key key);
/**
* Returns the provider used to obtain instances for the given injection type.
* The returned provider will not be valid until the {@link Injector} has been
* created. The provider will throw an {@code IllegalStateException} if you
* try to use it beforehand.
*
* @since 2.0
*/
Provider getProvider(Class type);
/**
* Returns the members injector used to inject dependencies into methods and fields on instances
* of the given type {@code T}. The returned members injector will not be valid until the main
* {@link Injector} has been created. The members injector will throw an {@code
* IllegalStateException} if you try to use it beforehand.
*
* @param typeLiteral type to get members injector for
* @since 2.0
*/
MembersInjector getMembersInjector(TypeLiteral typeLiteral);
/**
* Returns the members injector used to inject dependencies into methods and fields on instances
* of the given type {@code T}. The returned members injector will not be valid until the main
* {@link Injector} has been created. The members injector will throw an {@code
* IllegalStateException} if you try to use it beforehand.
*
* @param type type to get members injector for
* @since 2.0
*/
MembersInjector getMembersInjector(Class type);
/**
* Binds a type converter. The injector will use the given converter to
* convert string constants to matching types as needed.
*
* @param typeMatcher matches types the converter can handle
* @param converter converts values
* @since 2.0
*/
void convertToTypes(Matcher> typeMatcher,
TypeConverter converter);
/**
* Registers a listener for injectable types. Guice will notify the listener when it encounters
* injectable types matched by the given type matcher.
*
* @param typeMatcher that matches injectable types the listener should be notified of
* @param listener for injectable types matched by typeMatcher
* @since 2.0
*/
void bindListener(Matcher> typeMatcher,
TypeListener listener);
/**
* Returns a binder that uses {@code source} as the reference location for
* configuration errors. This is typically a {@link StackTraceElement}
* for {@code .java} source but it could any binding source, such as the
* path to a {@code .properties} file.
*
* @param source any object representing the source location and has a
* concise {@link Object#toString() toString()} value
* @return a binder that shares its configuration with this binder
* @since 2.0
*/
Binder withSource(Object source);
/**
* Returns a binder that skips {@code classesToSkip} when identify the
* calling code. The caller's {@link StackTraceElement} is used to locate
* the source of configuration errors.
*
* @param classesToSkip library classes that create bindings on behalf of
* their clients.
* @return a binder that shares its configuration with this binder.
* @since 2.0
*/
Binder skipSources(Class... classesToSkip);
/**
* 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 {@link
* PrivateModule} for details.
*
* @return a binder that inherits configuration from this binder. Only exposed configuration on
* the returned binder will be visible to this binder.
* @since 2.0
*/
PrivateBinder newPrivateBinder();
}