home | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (ProviderMethod.java)

This example Java source code file (ProviderMethod.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

annotation, class, errorsexception, factory, illegalaccessexception, immutableset, internalfactory, invocationtargetexception, key, list, object, override, providermethod, reflection, suppresswarnings, util

The ProviderMethod.java Java example source code

/**
 * Copyright (C) 2008 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 com.google.inject.internal;

import com.google.common.base.Objects;
import com.google.common.collect.ImmutableSet;
import com.google.inject.Binder;
import com.google.inject.Exposed;
import com.google.inject.Key;
import com.google.inject.PrivateBinder;
import com.google.inject.Provider;
import com.google.inject.Provides;
import com.google.inject.internal.ProvisionListenerStackCallback.ProvisionCallback;
import com.google.inject.internal.util.StackTraceElements;
import com.google.inject.spi.BindingTargetVisitor;
import com.google.inject.spi.Dependency;
import com.google.inject.spi.HasDependencies;
import com.google.inject.spi.InjectionPoint;
import com.google.inject.spi.ProviderInstanceBinding;
import com.google.inject.spi.ProviderWithExtensionVisitor;
import com.google.inject.spi.ProvidesMethodBinding;
import com.google.inject.spi.ProvidesMethodTargetVisitor;

import java.lang.annotation.Annotation;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.List;
import java.util.Set;

/**
 * A provider that invokes a method and returns its result.
 *
 * @author jessewilson@google.com (Jesse Wilson)
 */
public abstract class ProviderMethod<T> implements ProviderWithExtensionVisitor, HasDependencies,
    ProvidesMethodBinding<T> {

  /**
   * Creates a {@link ProviderMethod}.
   *
   * <p>Unless {@code skipFastClassGeneration} is set, this will use
   * {@link net.sf.cglib.reflect.FastClass} to invoke the actual method, since it is significantly
   * faster. However, this will fail if the method is {@code private} or {@code protected}, since
   * fastclass is subject to java access policies.
   */
  static <T> ProviderMethod create(Key key, Method method, Object instance,
      ImmutableSet<Dependency dependencies, List> parameterProviders,
      Class<? extends Annotation> scopeAnnotation, boolean skipFastClassGeneration,
      Annotation annotation) {
    int modifiers = method.getModifiers();
    /*if[AOP]*/
    if (!skipFastClassGeneration) {
      try {
        net.sf.cglib.reflect.FastClass fc = BytecodeGen.newFastClassForMember(method);
        if (fc != null) {
          return new FastClassProviderMethod<T>(key,
              fc,
              method,
              instance,
              dependencies,
              parameterProviders,
              scopeAnnotation,
              annotation);
        }
      } catch (net.sf.cglib.core.CodeGenerationException e) {/* fall-through */}
    }
    /*end[AOP]*/

    if (!Modifier.isPublic(modifiers) ||
        !Modifier.isPublic(method.getDeclaringClass().getModifiers())) {
      method.setAccessible(true);
    }

    return new ReflectionProviderMethod<T>(key,
        method,
        instance,
        dependencies,
        parameterProviders,
        scopeAnnotation,
        annotation);
  }

  protected final Object instance;
  protected final Method method;

  private final Key<T> key;
  private final Class<? extends Annotation> scopeAnnotation;
  private final ImmutableSet<Dependency dependencies;
  private final List<Provider parameterProviders;
  private final boolean exposed;
  private final Annotation annotation;

  /**
   * @param method the method to invoke. It's return type must be the same type as {@code key}.
   */
  private ProviderMethod(Key<T> key, Method method, Object instance,
      ImmutableSet<Dependency dependencies, List> parameterProviders,
      Class<? extends Annotation> scopeAnnotation, Annotation annotation) {
    this.key = key;
    this.scopeAnnotation = scopeAnnotation;
    this.instance = instance;
    this.dependencies = dependencies;
    this.method = method;
    this.parameterProviders = parameterProviders;
    this.exposed = method.isAnnotationPresent(Exposed.class);
    this.annotation = annotation;
  }

  @Override
  public Key<T> getKey() {
    return key;
  }

  @Override
  public Method getMethod() {
    return method;
  }

  // exposed for GIN
  public Object getInstance() {
    return instance;
  }
  
  @Override
  public Object getEnclosingInstance() {
    return instance;
  }
  
  @Override
  public Annotation getAnnotation() {
    return annotation;
  }

  public void configure(Binder binder) {
    binder = binder.withSource(method);

    if (scopeAnnotation != null) {
      binder.bind(key).toProvider(this).in(scopeAnnotation);
    } else {
      binder.bind(key).toProvider(this);
    }

    if (exposed) {
      // the cast is safe 'cause the only binder we have implements PrivateBinder. If there's a
      // misplaced @Exposed, calling this will add an error to the binder's error queue
      ((PrivateBinder) binder).expose(key);
    }
  }

  @Override
  public T get() {
    Object[] parameters = new Object[parameterProviders.size()];
    for (int i = 0; i < parameters.length; i++) {
      parameters[i] = parameterProviders.get(i).get();
    }

    try {
      return doProvision(parameters);
    } catch (IllegalAccessException e) {
      throw new AssertionError(e);
    } catch (InvocationTargetException e) {
      throw Exceptions.rethrowCause(e);
    }
  }

  /** Extension point for our subclasses to implement the provisioning strategy. */
  abstract T doProvision(Object[] parameters)
      throws IllegalAccessException, InvocationTargetException;

  @Override
  public Set<Dependency getDependencies() {
    return dependencies;
  }
  
  @Override
  @SuppressWarnings("unchecked")
  public <B, V> V acceptExtensionVisitor(BindingTargetVisitor visitor,
      ProviderInstanceBinding<? extends B> binding) {
    if (visitor instanceof ProvidesMethodTargetVisitor) {
      return ((ProvidesMethodTargetVisitor<T, V>)visitor).visit(this);
    }
    return visitor.visit(binding);
  }

  @Override public String toString() {
    String annotationString = annotation.toString();
    // Show @Provides w/o the com.google.inject prefix.
    if (annotation.annotationType() == Provides.class) {
      annotationString = "@Provides";
    } else if (annotationString.endsWith("()")) {
      // Remove the common "()" suffix if there are no values.
      annotationString = annotationString.substring(0, annotationString.length() - 2);
    }
    return annotationString + " " + StackTraceElements.forMember(method);
  }
  
  @Override
  public boolean equals(Object obj) {
    if (obj instanceof ProviderMethod) {
      ProviderMethod<?> o = (ProviderMethod) obj;
      return method.equals(o.method)
         && instance.equals(o.instance)
         && annotation.equals(o.annotation);
    } else {
      return false;
    }
  }
  
  @Override
  public int hashCode() {
    // Avoid calling hashCode on 'instance', which is a user-object
    // that might not be expecting it.
    // (We need to call equals, so we do.  But we can avoid hashCode.)
    return Objects.hashCode(method, annotation);
  }

  /*if[AOP]*/
  /**
   * A {@link ProviderMethod} implementation that uses {@link net.sf.cglib.reflect.FastClass#invoke}
   * to invoke the provider method.
   */
  private static final class FastClassProviderMethod<T> extends ProviderMethod {
    final net.sf.cglib.reflect.FastClass fastClass;
    final int methodIndex;

    FastClassProviderMethod(Key<T> key,
        net.sf.cglib.reflect.FastClass fc, 
        Method method,
        Object instance,
        ImmutableSet<Dependency dependencies,
        List<Provider parameterProviders,
        Class<? extends Annotation> scopeAnnotation,
        Annotation annotation) {
      super(key,
          method,
          instance,
          dependencies,
          parameterProviders,
          scopeAnnotation,
          annotation);
      this.fastClass = fc;
      this.methodIndex = fc.getMethod(method).getIndex();
    }

    @SuppressWarnings("unchecked")
    @Override
    public T doProvision(Object[] parameters)
        throws IllegalAccessException, InvocationTargetException {
      return (T) fastClass.invoke(methodIndex, instance, parameters);
    }
  }
  /*end[AOP]*/

  /**
   * A {@link ProviderMethod} implementation that invokes the method using normal java reflection. 
   */
  private static final class ReflectionProviderMethod<T> extends ProviderMethod {
    ReflectionProviderMethod(Key<T> key,
        Method method,
        Object instance,
        ImmutableSet<Dependency dependencies,
        List<Provider parameterProviders,
        Class<? extends Annotation> scopeAnnotation,
        Annotation annotation) {
      super(key,
          method,
          instance,
          dependencies,
          parameterProviders,
          scopeAnnotation,
          annotation);
    }

    @SuppressWarnings("unchecked")
    @Override
    T doProvision(Object[] parameters) throws IllegalAccessException, InvocationTargetException {
      return (T) method.invoke(instance, parameters);
    }
  }

  static <T> BindingImpl createBinding(
      InjectorImpl injector,
      Key<T> key,
      ProviderMethod<T> providerMethod,
      Object source,
      Scoping scoping) {
    Factory<T> factory = new Factory(source, providerMethod);
    InternalFactory<? extends T> scopedFactory =
        Scoping.scope(key, injector, factory, source, scoping);
    return new ProviderMethodProviderInstanceBindingImpl<T>(
        injector, key, source, scopedFactory, scoping, providerMethod, factory);
  }

  private static final class ProviderMethodProviderInstanceBindingImpl<T>
      extends ProviderInstanceBindingImpl<T> implements DelayedInitialize {
    final Factory<T> factory;

    ProviderMethodProviderInstanceBindingImpl(
        InjectorImpl injector,
        Key<T> key,
        Object source,
        InternalFactory<? extends T> internalFactory,
        Scoping scoping,
        // TODO(lukes): it is a little strange that we expose the ProviderMethod as the
        // userProvider.  Maybe we should expose BindingImpl.getProvider() and then we could drop
        // the ProviderLookups stored by ProviderMethod.  It probably isn't a big deal either way
        // but having 2 ways to invoke the method is kind of weird.
        ProviderMethod<T> providerInstance,
        Factory<T> factory) {
      super(
          injector,
          key,
          source,
          internalFactory,
          scoping,
          providerInstance,
          ImmutableSet.<InjectionPoint>of());
      this.factory = factory;
    }

    @Override
    public void initialize(InjectorImpl injector, Errors errors) throws ErrorsException {
      factory.parameterInjectors =
          injector.getParametersInjectors(factory.providerMethod.dependencies.asList(), errors);
      factory.provisionCallback = injector.provisionListenerStore.get(this);
    }
  }

  private static final class Factory<T> implements InternalFactory {
    private final Object source;
    private final ProviderMethod<T> providerMethod;
    private ProvisionListenerStackCallback<T> provisionCallback;
    private SingleParameterInjector<?>[] parameterInjectors;

    Factory(Object source, ProviderMethod<T> providerMethod) {
      this.source = source;
      this.providerMethod = providerMethod;
    }

    @Override
    public T get(
        final Errors errors,
        final InternalContext context,
        final Dependency<?> dependency,
        boolean linked)
        throws ErrorsException {
      final ConstructionContext<T> constructionContext = context.getConstructionContext(this);
      // We have a circular reference between bindings. Return a proxy.
      if (constructionContext.isConstructing()) {
        Class<?> expectedType = dependency.getKey().getTypeLiteral().getRawType();
        // TODO: if we can't proxy this object, can we proxy the other object?
        @SuppressWarnings("unchecked")
        T proxyType =
            (T) constructionContext.createProxy(errors, context.getInjectorOptions(), expectedType);
        return proxyType;
      }
      // Optimization: Don't go through the callback stack if no one's listening.
      constructionContext.startConstruction();
      try {
        if (!provisionCallback.hasListeners()) {
          return provision(errors, dependency, context, constructionContext);
        } else {
          return provisionCallback.provision(
              errors,
              context,
              new ProvisionCallback<T>() {
                @Override
                public T call() throws ErrorsException {
                  return provision(errors, dependency, context, constructionContext);
                }
              });
        }
      } finally {
        constructionContext.removeCurrentReference();
        constructionContext.finishConstruction();
      }
    }

    T provision(
        Errors errors,
        Dependency<?> dependency,
        InternalContext context,
        ConstructionContext<T> constructionContext)
        throws ErrorsException {
      try {
        T t = providerMethod.doProvision(
            SingleParameterInjector.getAll(errors, context, parameterInjectors));
        errors.checkForNull(t, providerMethod.getMethod(), dependency);
        constructionContext.setProxyDelegates(t);
        return t;
      } catch (IllegalAccessException e) {
        throw new AssertionError(e);
      } catch (InvocationTargetException userException) {
        Throwable cause =
            userException.getCause() != null ? userException.getCause() : userException;
        throw errors
            .withSource(source)
            .errorInProvider(cause)
            .toException();
      }
    }
    
    @Override
    public String toString() {
      return providerMethod.toString();
    }
  }
}

Other Java examples (source code examples)

Here is a short list of links related to this Java ProviderMethod.java source code file:



my book on functional programming

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.