| com.bm.ejb3guice.inject.Binder
All known Subclasses: com.bm.ejb3guice.inject.BinderImpl,
| Binder | | public interface Binder (Code) | | 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 in the usual way -- by reading
method-level javadocs. Instead, you should consult this 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 @ImplementedBy or
ProvidedBy @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 . 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
Provider.get 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
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
@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.bm.ejb3guice.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 . The class
CreditCardPaymentService must implement the
PaymentService interface. Guice cannot currently bind or
inject a generic type, such as
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
ServiceImpl instance, then asks Guice to always use
this single instance to fulfill all
Service injection requests. When
the
Injector is first 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 bindings are typeless in Guice; you
can provide the values in a variety of types and the values can be injected
in a variety of types; Guice performs the standard type conversions for you
behind the scenes. Because of this "typelessness", constant injections must
always be annotated.
Color("red") Color red; // A member variable (field)
. . .
red = MyModule.class.getField("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,
com.bm.ejb3guice.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
Binder.bindScope ,
Binder.bindInterceptor ,
Binder.install ,
Binder.requestStaticInjection ,
Binder.addError and
Binder.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) |
| addError | | void addError(String message, Object... arguments)(Code) | | 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(StringObject[]) to insert the arguments into the
message.
|
| addError | | void addError(Throwable t)(Code) | | 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.
|
| bindInterceptor | | void bindInterceptor(Matcher<? super Class<?>> classMatcher, Matcher<? super Method> methodMatcher, MethodInterceptor... interceptors)(Code) | | Binds a method interceptor to methods matched by class and method
matchers.
Parameters:
classMatcher - matches classes the interceptor should apply to. Forexample: only(Runnable.class) .
Parameters:
methodMatcher - matches methods the interceptor should apply to. Forexample: annotatedWith(Transactional.class) .
Parameters:
interceptors - to bind |
| currentStage | | Stage currentStage()(Code) | | Gets the current stage.
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| getProvider | | Provider<T> getProvider(Key<T> key)(Code) | | 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.
|
| getProvider | | Provider<T> getProvider(Class<T> type)(Code) | | Returns the provider used to obtain instances for the given injection type.
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.
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| install | | void install(Module module)(Code) | | Uses the given module to configure more bindings.
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| requestStaticInjection | | void requestStaticInjection(Class... types)(Code) | | Upon successful creation, the
Injector will inject static fields
and methods in the given classes.
Parameters:
types - for which static members will be injected |
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