org.elasticsearch.common.inject.multibindings

Class MapBinder<K,V>

java.lang.Object

org.elasticsearch.common.inject.multibindings.MapBinder<K,V>

Direct Known Subclasses:

MapBinder.RealMapBinder

public abstract class MapBinder<K,V>
extends Object

An API to bind multiple map entries separately, only to later inject them as a complete map. MapBinder is intended for use in your application's module:

 public class SnacksModule extends AbstractModule {
   protected void configure() {
     MapBinder<String, Snack> mapbinder
         = MapBinder.newMapBinder(binder(), String.class, Snack.class);
     mapbinder.addBinding("twix").toInstance(new Twix());
     mapbinder.addBinding("snickers").toProvider(SnickersProvider.class);
     mapbinder.addBinding("skittles").to(Skittles.class);
   }
 }

With this binding, a Map<String, Snack> can now be injected:

 class SnackMachine {
   @Inject
   public SnackMachine(Map<String, Snack> snacks) { ... }
 }

In addition to binding Map<K, V>, a mapbinder will also bind Map<K, Provider<V>> for lazy value provision:

 class SnackMachine {
   @Inject
   public SnackMachine(Map<String, Provider<Snack>> snackProviders) { ... }
 }

Creating mapbindings from different modules is supported. For example, it is okay to have both CandyModule and ChipsModule both create their own MapBinder<String, Snack>, and to each contribute bindings to the snacks map. When that map is injected, it will contain entries from both modules.

Values are resolved at map injection time. If a value is bound to a provider, that provider's get method will be called each time the map is injected (unless the binding is also scoped, or a map of providers is injected).

Annotations are used to create different maps of the same key/value type. Each distinct annotation gets its own independent map.

Keys must be distinct. If the same key is bound more than once, map injection will fail.

Keys must be non-null. addBinding(null) will throw an unchecked exception.

Values must be non-null to use map injection. If any value is null, map injection will fail (although injecting a map of providers will not).

Author:

[email protected] (David P. Baker)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MapBinder.RealMapBinder<K,V> The actual mapbinder plays several roles:

Method Summary

Methods

Modifier and Type	Method and Description
abstract LinkedBindingBuilder<V>	addBinding(K key) Returns a binding builder used to add a new entry in the map.
static <K,V> MapBinder<K,V>	newMapBinder(Binder binder, Class<K> keyType, Class<V> valueType) Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with no binding annotation.
static <K,V> MapBinder<K,V>	newMapBinder(Binder binder, Class<K> keyType, Class<V> valueType, Annotation annotation) Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with annotation.
static <K,V> MapBinder<K,V>	newMapBinder(Binder binder, Class<K> keyType, Class<V> valueType, Class<? extends Annotation> annotationType) Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with annotationType.
static <K,V> MapBinder<K,V>	newMapBinder(Binder binder, TypeLiteral<K> keyType, TypeLiteral<V> valueType) Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with no binding annotation.
static <K,V> MapBinder<K,V>	newMapBinder(Binder binder, TypeLiteral<K> keyType, TypeLiteral<V> valueType, Annotation annotation) Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with annotation.
static <K,V> MapBinder<K,V>	newMapBinder(Binder binder, TypeLiteral<K> keyType, TypeLiteral<V> valueType, Class<? extends Annotation> annotationType) Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with annotationType.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

newMapBinder

public static <K,V> MapBinder<K,V> newMapBinder(Binder binder,
                                TypeLiteral<K> keyType,
                                TypeLiteral<V> valueType)

Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with no binding annotation.

newMapBinder

public static <K,V> MapBinder<K,V> newMapBinder(Binder binder,
                                Class<K> keyType,
                                Class<V> valueType)

Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with no binding annotation.

newMapBinder

public static <K,V> MapBinder<K,V> newMapBinder(Binder binder,
                                TypeLiteral<K> keyType,
                                TypeLiteral<V> valueType,
                                Annotation annotation)

Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with annotation.

newMapBinder

public static <K,V> MapBinder<K,V> newMapBinder(Binder binder,
                                Class<K> keyType,
                                Class<V> valueType,
                                Annotation annotation)

Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with annotation.

newMapBinder

public static <K,V> MapBinder<K,V> newMapBinder(Binder binder,
                                TypeLiteral<K> keyType,
                                TypeLiteral<V> valueType,
                                Class<? extends Annotation> annotationType)

Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with annotationType.

newMapBinder

public static <K,V> MapBinder<K,V> newMapBinder(Binder binder,
                                Class<K> keyType,
                                Class<V> valueType,
                                Class<? extends Annotation> annotationType)

Returns a new mapbinder that collects entries of keyType/valueType in a Map that is itself bound with annotationType.

addBinding

public abstract LinkedBindingBuilder<V> addBinding(K key)

Returns a binding builder used to add a new entry in the map. Each key must be distinct (and non-null). Bound providers will be evaluated each time the map is injected.

It is an error to call this method without also calling one of the to methods on the returned binding builder.

Scoping elements independently is supported. Use the in method to specify a binding scope.