containerimpl.java

在Struts2中的jar包xwork的源代码.版本为2.0.7

      new ReferenceCache<Class<?>, ConstructorInjector>() {
        @SuppressWarnings("unchecked")
        protected ConstructorInjector<?> create(Class<?> implementation) {
          return new ConstructorInjector(ContainerImpl.this, implementation);
        }
      };

  static class ConstructorInjector<T> {

    final Class<T> implementation;
    final List<Injector> injectors;
    final Constructor<T> constructor;
    final ParameterInjector<?>[] parameterInjectors;

    ConstructorInjector(ContainerImpl container, Class<T> implementation) {
      this.implementation = implementation;

      constructor = findConstructorIn(implementation);
      constructor.setAccessible(true);

      try {
        Inject inject = constructor.getAnnotation(Inject.class);
        parameterInjectors = inject == null
            ? null // default constructor.
            : container.getParametersInjectors(
                constructor,
                constructor.getParameterAnnotations(),
                constructor.getParameterTypes(),
                inject.value()
              );
      } catch (MissingDependencyException e) {
        throw new DependencyException(e);
      }
      injectors = container.injectors.get(implementation);
    }

    @SuppressWarnings("unchecked")
    private Constructor<T> findConstructorIn(Class<T> implementation) {
      Constructor<T> found = null;
      Constructor<T>[] declaredConstructors = (Constructor<T>[]) implementation
                    .getDeclaredConstructors();
      for(Constructor<T> constructor :  declaredConstructors) {
        if (constructor.getAnnotation(Inject.class) != null) {
          if (found != null) {
            throw new DependencyException("More than one constructor annotated"
              + " with @Inject found in " + implementation + ".");
          }
          found = constructor;
        }
      }
      if (found != null) {
        return found;
      }

      // If no annotated constructor is found, look for a no-arg constructor
      // instead.
      try {
        return implementation.getDeclaredConstructor();
      } catch (NoSuchMethodException e) {
        throw new DependencyException("Could not find a suitable constructor"
            + " in " + implementation.getName() + ".");
      }
    }

    /**
     * Construct an instance. Returns {@code Object} instead of {@code T}
     * because it may return a proxy.
     */
    Object construct(InternalContext context, Class<? super T> expectedType) {
      ConstructionContext<T> constructionContext =
          context.getConstructionContext(this);

      // We have a circular reference between constructors. Return a proxy.
      if (constructionContext.isConstructing()) {
        // TODO (crazybob): if we can't proxy this object, can we proxy the
        // other object?
        return constructionContext.createProxy(expectedType);
      }

      // If we're re-entering this factory while injecting fields or methods,
      // return the same instance. This prevents infinite loops.
      T t = constructionContext.getCurrentReference();
      if (t != null) {
        return t;
      }

      try {
        // First time through...
        constructionContext.startConstruction();
        try {
          Object[] parameters =
              getParameters(constructor, context, parameterInjectors);
          t = constructor.newInstance(parameters);
          constructionContext.setProxyDelegates(t);
        } finally {
          constructionContext.finishConstruction();
        }

        // Store reference. If an injector re-enters this factory, they'll
        // get the same reference.
        constructionContext.setCurrentReference(t);

        // Inject fields and methods.
        for (Injector injector : injectors) {
          injector.inject(context, t);
        }

        return t;
      } catch (InstantiationException e) {
        throw new RuntimeException(e);
      } catch (IllegalAccessException e) {
        throw new RuntimeException(e);
      } catch (InvocationTargetException e) {
        throw new RuntimeException(e);
      } finally {
        constructionContext.removeCurrentReference();
      }
    }
  }

  static class ParameterInjector<T> {

    final ExternalContext<T> externalContext;
    final InternalFactory<? extends T> factory;

    public ParameterInjector(ExternalContext<T> externalContext,
        InternalFactory<? extends T> factory) {
      this.externalContext = externalContext;
      this.factory = factory;
    }

    T inject(Member member, InternalContext context) {
      ExternalContext<?> previous = context.getExternalContext();
      context.setExternalContext(externalContext);
      try {
        return factory.create(context);
      } finally {
        context.setExternalContext(previous);
      }
    }
  }

  private static Object[] getParameters(Member member, InternalContext context,
      ParameterInjector[] parameterInjectors) {
    if (parameterInjectors == null) {
      return null;
    }

    Object[] parameters = new Object[parameterInjectors.length];
    for (int i = 0; i < parameters.length; i++) {
      parameters[i] = parameterInjectors[i].inject(member, context);
    }
    return parameters;
  }

  void inject(Object o, InternalContext context) {
    List<Injector> injectors = this.injectors.get(o.getClass());
    for (Injector injector : injectors) {
      injector.inject(context, o);
    }
  }

  <T> T inject(Class<T> implementation, InternalContext context) {
    try {
      ConstructorInjector<T> constructor = getConstructor(implementation);
      return implementation.cast(
          constructor.construct(context, implementation));
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  @SuppressWarnings("unchecked")
  <T> T getInstance(Class<T> type, String name, InternalContext context) {
    ExternalContext<?> previous = context.getExternalContext();
    Key<T> key = Key.newInstance(type, name);
    context.setExternalContext(ExternalContext.newInstance(null, key, this));
    try {
      InternalFactory o = getFactory(key);
      if (o != null) {
          return getFactory(key).create(context);
      } else {
          return null;
      }
    } finally {
      context.setExternalContext(previous);
    }
  }

  <T> T getInstance(Class<T> type, InternalContext context) {
    return getInstance(type, DEFAULT_NAME, context);
  }

  public void inject(final Object o) {
    callInContext(new ContextualCallable<Void>() {
      public Void call(InternalContext context) {
        inject(o, context);
        return null;
      }
    });
  }

  public <T> T inject(final Class<T> implementation) {
    return callInContext(new ContextualCallable<T>() {
      public T call(InternalContext context) {
        return inject(implementation, context);
      }
    });
  }

  public <T> T getInstance(final Class<T> type, final String name) {
    return callInContext(new ContextualCallable<T>() {
      public T call(InternalContext context) {
        return getInstance(type, name, context);
      }
    });
  }

  public <T> T getInstance(final Class<T> type) {
    return callInContext(new ContextualCallable<T>() {
      public T call(InternalContext context) {
        return getInstance(type, context);
      }
    });
  }
  
  public Set<String> getInstanceNames(final Class<?> type) {
    return factoryNamesByType.get(type);
  }

  ThreadLocal<Object[]> localContext =
      new ThreadLocal<Object[]>() {
        protected InternalContext[] initialValue() {
          return new InternalContext[1];
        }
      };

  /**
   * Looks up thread local context. Creates (and removes) a new context if
   * necessary.
   */
  <T> T callInContext(ContextualCallable<T> callable) {
    InternalContext[] reference = (InternalContext[]) localContext.get();
    if (reference[0] == null) {
      reference[0] = new InternalContext(this);
      try {
        return callable.call(reference[0]);
      } finally {
        // Only remove the context if this call created it.
        reference[0] = null;
      }
    } else {
      // Someone else will clean up this context.
      return callable.call(reference[0]);
    }
  }

  interface ContextualCallable<T> {
    T call(InternalContext context);
  }

  /**
   * Gets a constructor function for a given implementation class.
   */
  @SuppressWarnings("unchecked")
  <T> ConstructorInjector<T> getConstructor(Class<T> implementation) {
    return constructors.get(implementation);
  }

  final ThreadLocal<Object> localScopeStrategy =
      new ThreadLocal<Object>();

  public void setScopeStrategy(Scope.Strategy scopeStrategy) {
    this.localScopeStrategy.set(scopeStrategy);
  }

  public void removeScopeStrategy() {
    this.localScopeStrategy.remove();
  }

  /**
   * Injects a field or method in a given object.
   */
  interface Injector extends Serializable {
    void inject(InternalContext context, Object o);
  }

  static class MissingDependencyException extends Exception {

    MissingDependencyException(String message) {
      super(message);
    }
  }
}