Struts example source code file (ContainerImpl.java)

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

Java - Struts tags/keywords

annotation, class, class, dependencyexception, injector, internalfactory, io, list, list, missingdependencyexception, missingdependencyexception, object, parameterinjector, reflection, security, string, t, t, util

The Struts ContainerImpl.java source code

/**
 * Copyright (C) 2006 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.opensymphony.xwork2.inject;

import com.opensymphony.xwork2.inject.util.ReferenceCache;

import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.lang.reflect.*;
import java.util.*;
import java.util.Map.Entry;
import java.security.AccessControlException;

/**
 * Default {@link Container} implementation.
 *
 * @see ContainerBuilder
 * @author crazybob@google.com (Bob Lee)
 */
class ContainerImpl implements Container {

  final Map<Key> factories;
  final Map<Class> factoryNamesByType;

  ContainerImpl(Map<Key> factories) {
    this.factories = factories;
    Map<Class> map = new HashMap,Set>();
    for (Key<?> key : factories.keySet()) {
      Set<String> names = map.get(key.getType());
      if (names == null) {
        names = new HashSet<String>();
        map.put(key.getType(), names);
      }
      names.add(key.getName());
    }
    
    for (Entry<Class> entry : map.entrySet()) {
      entry.setValue(Collections.unmodifiableSet(entry.getValue()));
    }
    
    this.factoryNamesByType = Collections.unmodifiableMap(map);
  }

  @SuppressWarnings("unchecked")
  <T> InternalFactory getFactory(Key key) {
    return (InternalFactory<T>) factories.get(key);
  }

  /**
   * Field and method injectors.
   */
  final Map<Class> injectors =
      new ReferenceCache<Class>() {
        @Override
        protected List<Injector> create(Class key) {
          List<Injector> injectors = new ArrayList();
          addInjectors(key, injectors);
          return injectors;
        }
      };

  /**
   * Recursively adds injectors for fields and methods from the given class to
   * the given list. Injects parent classes before sub classes.
   */
  void addInjectors(Class clazz, List<Injector> injectors) {
    if (clazz == Object.class) {
      return;
    }

    // Add injectors for superclass first.
    addInjectors(clazz.getSuperclass(), injectors);

    // TODO (crazybob): Filter out overridden members.
    addInjectorsForFields(clazz.getDeclaredFields(), false, injectors);
    addInjectorsForMethods(clazz.getDeclaredMethods(), false, injectors);
  }

  void injectStatics(List<Class staticInjections) {
    final List<Injector> injectors = new ArrayList();

    for (Class<?> clazz : staticInjections) {
      addInjectorsForFields(clazz.getDeclaredFields(), true, injectors);
      addInjectorsForMethods(clazz.getDeclaredMethods(), true, injectors);
    }

    callInContext(new ContextualCallable<Void>() {
      public Void call(InternalContext context) {
        for (Injector injector : injectors) {
          injector.inject(context, null);
        }
        return null;
      }
    });
  }

  void addInjectorsForMethods(Method[] methods, boolean statics,
      List<Injector> injectors) {
    addInjectorsForMembers(Arrays.asList(methods), statics, injectors,
        new InjectorFactory<Method>() {
          public Injector create(ContainerImpl container, Method method,
              String name) throws MissingDependencyException {
            return new MethodInjector(container, method, name);
          }
        });
  }

  void addInjectorsForFields(Field[] fields, boolean statics,
      List<Injector> injectors) {
    addInjectorsForMembers(Arrays.asList(fields), statics, injectors,
        new InjectorFactory<Field>() {
          public Injector create(ContainerImpl container, Field field,
              String name) throws MissingDependencyException {
            return new FieldInjector(container, field, name);
          }
        });
  }

  <M extends Member & AnnotatedElement> void addInjectorsForMembers(
      List<M> members, boolean statics, List injectors,
      InjectorFactory<M> injectorFactory) {
    for (M member : members) {
      if (isStatic(member) == statics) {
        Inject inject = member.getAnnotation(Inject.class);
        if (inject != null) {
          try {
            injectors.add(injectorFactory.create(this, member, inject.value()));
          } catch (MissingDependencyException e) {
            if (inject.required()) {
              throw new DependencyException(e);
            }
          }
        }
      }
    }
  }

  interface InjectorFactory<M extends Member & AnnotatedElement> {
    Injector create(ContainerImpl container, M member, String name)
        throws MissingDependencyException;
  }

  private boolean isStatic(Member member) {
    return Modifier.isStatic(member.getModifiers());
  }

  static class FieldInjector implements Injector {

    final Field field;
    final InternalFactory<?> factory;
    final ExternalContext<?> externalContext;

    public FieldInjector(ContainerImpl container, Field field, String name)
        throws MissingDependencyException {
      this.field = field;
        if (!field.isAccessible()) {
            SecurityManager sm = System.getSecurityManager();
            try {
                if (sm != null) sm.checkPermission(new ReflectPermission("suppressAccessChecks"));
                field.setAccessible(true);
            } catch(AccessControlException e) {
                throw new DependencyException("Security manager in use, could not access field: "
                        + field.getDeclaringClass().getName() + "(" + field.getName() + ")", e);
            }
        }

      Key<?> key = Key.newInstance(field.getType(), name);
      factory = container.getFactory(key);
      if (factory == null) {
        throw new MissingDependencyException(
            "No mapping found for dependency " + key + " in " + field + ".");
      }

      this.externalContext = ExternalContext.newInstance(field, key, container);
    }

    public void inject(InternalContext context, Object o) {
      ExternalContext<?> previous = context.getExternalContext();
      context.setExternalContext(externalContext);
      try {
        field.set(o, factory.create(context));
      } catch (IllegalAccessException e) {
        throw new AssertionError(e);
      } finally {
        context.setExternalContext(previous);
      }
    }
  }

  /**
   * Gets parameter injectors.
   *
   * @param member to which the parameters belong
   * @param annotations on the parameters
   * @param parameterTypes parameter types
   * @return injections
   */
  <M extends AccessibleObject & Member> ParameterInjector[]
      getParametersInjectors(M member,
      Annotation[][] annotations, Class[] parameterTypes, String defaultName)
      throws MissingDependencyException {
    List<ParameterInjector parameterInjectors =
        new ArrayList<ParameterInjector();

    Iterator<Annotation[]> annotationsIterator =
        Arrays.asList(annotations).iterator();
    for (Class<?> parameterType : parameterTypes) {
      Inject annotation = findInject(annotationsIterator.next());
      String name = annotation == null ? defaultName : annotation.value();
      Key<?> key = Key.newInstance(parameterType, name);
      parameterInjectors.add(createParameterInjector(key, member));
    }

    return toArray(parameterInjectors);
  }

  <T> ParameterInjector createParameterInjector(
      Key<T> key, Member member) throws MissingDependencyException {
    InternalFactory<? extends T> factory = getFactory(key);
    if (factory == null) {
      throw new MissingDependencyException(
          "No mapping found for dependency " + key + " in " + member + ".");
    }

    ExternalContext<T> externalContext =
        ExternalContext.newInstance(member, key, this);
    return new ParameterInjector<T>(externalContext, factory);
  }

  @SuppressWarnings("unchecked")
  private ParameterInjector<?>[] toArray(
      List<ParameterInjector parameterInjections) {
    return parameterInjections.toArray(
        new ParameterInjector[parameterInjections.size()]);
  }

  /**
   * Finds the {@link Inject} annotation in an array of annotations.
   */
  Inject findInject(Annotation[] annotations) {
    for (Annotation annotation : annotations) {
      if (annotation.annotationType() == Inject.class) {
        return Inject.class.cast(annotation);
      }
    }
    return null;
  }

  static class MethodInjector implements Injector {

    final Method method;
    final ParameterInjector<?>[] parameterInjectors;

    public MethodInjector(ContainerImpl container, Method method, String name)
        throws MissingDependencyException {
      this.method = method;
        if (!method.isAccessible()) {
            SecurityManager sm = System.getSecurityManager();
            try {
                if (sm != null) sm.checkPermission(new ReflectPermission("suppressAccessChecks"));
                method.setAccessible(true);
            } catch(AccessControlException e) {
                throw new DependencyException("Security manager in use, could not access method: "
                        + name + "(" + method.getName() + ")", e);
            }
        }

      Class<?>[] parameterTypes = method.getParameterTypes();
      if (parameterTypes.length == 0) {
        throw new DependencyException(
            method + " has no parameters to inject.");
      }
      parameterInjectors = container.getParametersInjectors(
          method, method.getParameterAnnotations(), parameterTypes, name);
    }

    public void inject(InternalContext context, Object o) {
      try {
        method.invoke(o, getParameters(method, context, parameterInjectors));
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
  }

  Map<Class constructors =
      new ReferenceCache<Class() {
        @Override
        @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);
        if (!constructor.isAccessible()) {
            SecurityManager sm = System.getSecurityManager();
            try {
                if (sm != null) sm.checkPermission(new ReflectPermission("suppressAccessChecks"));
                constructor.setAccessible(true);
            } catch(AccessControlException e) {
                throw new DependencyException("Security manager in use, could not access constructor: "
                        + implementation.getName() + "(" + constructor.getName() + ")", e);
            }
        }

      MissingDependencyException exception = null;
      Inject inject = null;
      ParameterInjector<?>[] parameters = null;
        
      try {
        inject = constructor.getAnnotation(Inject.class);
        parameters = constructParameterInjector(inject, container, constructor);
      } catch (MissingDependencyException e) {
        exception = e;
      }
      parameterInjectors = parameters;

      if ( exception != null) {
        if ( inject != null && inject.required()) {
          throw new DependencyException(exception);
        }
      }
      injectors = container.injectors.get(implementation);
    }

    ParameterInjector<?>[] constructParameterInjector(
    Inject inject, ContainerImpl container, Constructor<T> constructor) throws MissingDependencyException{
    return constructor.getParameterTypes().length == 0
      ? null // default constructor.
      : container.getParametersInjectors(
        constructor,
        constructor.getParameterAnnotations(),
        constructor.getParameterTypes(),
        inject.value()
      );
    }

    @SuppressWarnings("unchecked")
    private Constructor<T> findConstructorIn(Class implementation) {
      Constructor<T> found = null;
      Constructor<T>[] declaredConstructors = (Constructor[]) 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 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 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 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 implementation) {
    return callInContext(new ContextualCallable<T>() {
      public T call(InternalContext context) {
        return inject(implementation, context);
      }
    });
  }

  public <T> T getInstance(final Class 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 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[]>() {
        @Override
        protected Object[] initialValue() {
          return new Object[1];
        }
      };

  /**
   * Looks up thread local context. Creates (and removes) a new context if
   * necessary.
   */
  <T> T callInContext(ContextualCallable callable) {
    Object[] reference = localContext.get();
    if (reference[0] == null) {
      reference[0] = new InternalContext(this);
      try {
        return callable.call((InternalContext)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((InternalContext)reference[0]);
    }
  }

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

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