com.google.inject.servlet

Class ServletScopes

java.lang.Object

com.google.inject.servlet.ServletScopes

public class ServletScopes
extends Object

Servlet scopes.

Field Summary

Fields

Modifier and Type	Field and Description
static Scope	REQUEST HTTP servlet request scope.
static Scope	SESSION HTTP session scope.

Method Summary

Modifier and Type	Method and Description
static <T> Callable<T>	continueRequest(Callable<T> callable, Map<Key<?>,Object> seedMap) Wraps the given callable in a contextual callable that "continues" the HTTP request in another thread.
static boolean	isRequestScoped(Binding<?> binding) Returns true if binding is request-scoped.
static <T> Callable<T>	scopeRequest(Callable<T> callable, Map<Key<?>,Object> seedMap) Scopes the given callable inside a request scope.
static <T> Callable<T>	transferRequest(Callable<T> callable) Wraps the given callable in a contextual callable that "transfers" the request to another thread.

Methods inherited from class java.lang.Object

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

Field Detail

REQUEST

public static final Scope REQUEST

HTTP servlet request scope.

SESSION

public static final Scope SESSION

HTTP session scope.

Method Detail

continueRequest

public static <T> Callable<T> continueRequest(Callable<T> callable,
                                              Map<Key<?>,Object> seedMap)

Wraps the given callable in a contextual callable that "continues" the HTTP request in another thread. This acts as a way of transporting request context data from the request processing thread to to worker threads.

There are some limitations:

• Derived objects (i.e. anything marked @RequestScoped will not be transported.
• State changes to the HttpServletRequest after this method is called will not be seen in the continued thread.
• Only the HttpServletRequest, ServletContext and request parameter map are available in the continued thread. The response and session are not available.

The returned callable will throw a ScopingException when called if the HTTP request scope is still active on the current thread.

Parameters:

callable - code to be executed in another thread, which depends on the request scope.

seedMap - the initial set of scoped instances for Guice to seed the request scope with. To seed a key with null, use null as the value.

Returns:

a callable that will invoke the given callable, making the request context available to it.

Throws:

OutOfScopeException - if this method is called from a non-request thread, or if the request has completed.

Since:

3.0

transferRequest

public static <T> Callable<T> transferRequest(Callable<T> callable)

Wraps the given callable in a contextual callable that "transfers" the request to another thread. This acts as a way of transporting request context data from the current thread to a future thread.

As opposed to continueRequest(java.util.concurrent.Callable<T>, java.util.Map<com.google.inject.Key<?>, java.lang.Object>), this method propagates all existing scoped objects. The primary use case is in server implementations where you can detach the request processing thread while waiting for data, and reattach to a different thread to finish processing at a later time.

Because request-scoped objects are not typically thread-safe, the callable returned by this method must not be run on a different thread until the current request scope has terminated. The returned callable will block until the current thread has released the request scope.

Parameters:

callable - code to be executed in another thread, which depends on the request scope.

Returns:

a callable that will invoke the given callable, making the request context available to it.

Throws:

OutOfScopeException - if this method is called from a non-request thread, or if the request has completed.

Since:

4.0

isRequestScoped

public static boolean isRequestScoped(Binding<?> binding)

Returns true if binding is request-scoped. If the binding is a linked key binding and belongs to an injector (i. e. it was retrieved via Injector.getBinding()), then this method will also return true if the target binding is request-scoped.

Since:

4.0

scopeRequest

public static <T> Callable<T> scopeRequest(Callable<T> callable,
                                           Map<Key<?>,Object> seedMap)

Scopes the given callable inside a request scope. This is not the same as the HTTP request scope, but is used if no HTTP request scope is in progress. In this way, keys can be scoped as @RequestScoped and exist in non-HTTP requests (for example: RPC requests) as well as in HTTP request threads.

The returned callable will throw a ScopingException when called if there is a request scope already active on the current thread.

Parameters:

callable - code to be executed which depends on the request scope. Typically in another thread, but not necessarily so.

seedMap - the initial set of scoped instances for Guice to seed the request scope with. To seed a key with null, use null as the value.

Returns:

a callable that when called will run inside the a request scope that exposes the instances in the seedMap as scoped keys.

Since:

3.0