org.directwebremoting.guice.util.AbstractContextScope Maven / Gradle / Ivy

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DWR is easy Ajax for Java. It makes it simple to call Java code directly from Javascript. It gets rid of almost all the boiler plate code between the web browser and your Java code.
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/*
 * Copyright 2008 Tim Peierls
 *
 * 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 org.directwebremoting.guice.util;

import com.google.inject.Key;
import com.google.inject.Provider;
import com.google.inject.util.ToStringBuilder;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import static java.util.Collections.synchronizedList;

import static org.directwebremoting.guice.util.AbstractContextScope.State.CLOSED;
import static org.directwebremoting.guice.util.AbstractContextScope.State.OPEN;


/**
 * Partial implementation of {@link ContextScope}. Concrete implementations
 * must pass the context identifier type to the super constructor and define
 * {@code get()} to return the current context identifier (and to return null
 * or throw an exception if there is no current context). They must also implement
 * the {@link ContextRegistry} interface.
 * @author Tim Peierls [tim at peierls dot net]
 */
public abstract class AbstractContextScope implements ContextScope, ContextRegistry
{
    protected AbstractContextScope(Class type, String scopeName)
    {
        this.type = type;
        this.scopeName = scopeName;
    }

    /* (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString()
    {
        return scopeName;
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.guice.ContextScope#getKeysInScope()
     */
    public List> getKeysInScope()
    {
        synchronized (scopedKeys)
        {
            return new ArrayList>(scopedKeys);
        }
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.guice.ContextScope#scope(com.google.inject.Key, com.google.inject.Provider)
     */
    public  Provider scope(final Key key, final Provider creator)
    {
        scopedKeys.add(key);
        final String name = key.toString();
        return new Provider()
        {
            public T get()
            {
                C context = getContext(key);
                R registry = registryFor(context);
                InstanceProvider future = AbstractContextScope.this.get(registry, key, name);
                if (future == null)
                {
                    InstanceProvider futureTask = new FutureTaskProvider(creator);
                    future = putIfAbsent(registry, key, name, futureTask);
                    if (future == null)
                    {
                        future = futureTask;
                        futureTask.run();
                        if (Thread.currentThread().isInterrupted())
                        {
                            remove(registry, key, name, futureTask);
                        }
                    }
                }
                return future.get();
            }

            @Override
            public String toString()
            {
                return new ToStringBuilder(this.getClass())
                    .add("scopeName", scopeName)
                    .add("type", type)
                    .add("key", key)
                    .add("creator", creator)
                    .toString();
            }
        };
    }

    public abstract C get();

    /* (non-Javadoc)
     * @see org.directwebremoting.guice.ContextScope#type()
     */
    public Class type()
    {
        return type;
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.guice.ContextScope#getOpenContexts()
     */
    public Collection getOpenContexts()
    {
        Collection openContexts = new ArrayList();
        for (C context : contexts.keySet())
        {
            if (contexts.get(context) == OPEN)
            {
                openContexts.add(context);
            }
        }
        return openContexts;
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.guice.ContextScope#close(java.lang.Object, org.directwebremoting.guice.ContextCloseHandler[])
     */
    public void close(C context, ContextCloseHandler... closeHandlers)
    {
        if (!contexts.replace(context, OPEN, CLOSED))
        {
            // Context hadn't been opened or was already closed.
            return;
        }

        for (InstanceProvider provider : registeredProviders(registryFor(context)))
        {
            Object value = null;
            try
            {
                value = provider.get();
            }
            catch (RuntimeException e)
            {
                // Ignore runtime exceptions: they were thrown when
                // attempting creation and mean that no object was
                // created.
            }

            if (value == null)
            {
                // No instance was created by this provider, so we ignore.
                continue;
            }

            for (ContextCloseHandler closeHandler : closeHandlers)
            {
                handleClose(closeHandler, value);
            }
        }
    }

    /* (non-Javadoc)
     * @see org.directwebremoting.guice.ContextScope#closeAll(org.directwebremoting.guice.ContextCloseHandler[])
     */
    public void closeAll(ContextCloseHandler... closeHandlers)
    {
        for (C context : getOpenContexts())
        {
            close(context, closeHandlers);
        }
    }

    private  void handleClose(ContextCloseHandler closeHandler, Object value)
    {
        Class closeType = closeHandler.type();
        if (closeType.isInstance(value))
        {
            try
            {
                closeHandler.close(closeType.cast(value));
            }
            catch (Exception e)
            {
                // Ignore exceptions when closing,
                // the closeHandler should have taken
                // appropriate action before re-throwing.
            }
        }
    }

    protected C getContext(Key key)
    {
        C context = null;
        RuntimeException caught = null;
        try
        {
            context = get();
            if (contexts.putIfAbsent(context, OPEN) == CLOSED)
            {
                // Context is closed.
                context = null;
            }
        }
        catch (RuntimeException ex)
        {
            caught = ex;
        }
        if (context == null)
        {
            throw new OutOfScopeException(this, key, caught);
        }

        return context;
    }

    private Collection> registeredProviders(R registry)
    {
        List> providers = new ArrayList>();
        for (Key key : getKeysInScope())
        {
            InstanceProvider provider = get(registry, key, key.toString());
            if (provider != null)
            {
                providers.add(provider);
            }
        }
        return providers;
    }

    enum State
    {
        OPEN,
        CLOSED
    }

    protected final Class type;

    protected final String scopeName;

    /* @GuardedBy("self") */
    private final List> scopedKeys = synchronizedList(new ArrayList>());

    private final ConcurrentMap contexts = new ConcurrentHashMap();
}