package org.apache.velocity.runtime.resource;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Vector;
import org.apache.commons.collections.ExtendedProperties;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.RuntimeConstants;
import org.apache.velocity.runtime.RuntimeServices;
import org.apache.velocity.runtime.log.Log;
import org.apache.velocity.runtime.resource.loader.ResourceLoader;
import org.apache.velocity.runtime.resource.loader.ResourceLoaderFactory;
import org.apache.velocity.util.ClassUtils;
import org.apache.velocity.util.StringUtils;
/**
* Class to manage the text resource for the Velocity Runtime.
*
* @author <a href="mailto:[email protected]">Will Glass-Husain</a>
* @author <a href="mailto:[email protected]">Jason van Zyl</a>
* @author <a href="mailto:[email protected]">Paulo Gaspar</a>
* @author <a href="mailto:[email protected]">Geir Magnusson Jr.</a>
* @author <a href="mailto:[email protected]">Henning P. Schmiedehausen</a>
* @version $Id: ResourceManagerImpl.java 745760 2009-02-19 07:00:42Z nbubna $
*/
public class ResourceManagerImpl
implements ResourceManager
{
/** A template resources. */
public static final int RESOURCE_TEMPLATE = 1;
/** A static content resource. */
public static final int RESOURCE_CONTENT = 2;
/** token used to identify the loader internally. */
private static final String RESOURCE_LOADER_IDENTIFIER = "_RESOURCE_LOADER_IDENTIFIER_";
/** Object implementing ResourceCache to be our resource manager's Resource cache. */
protected ResourceCache globalCache = null;
/** The List of templateLoaders that the Runtime will use to locate the InputStream source of a template. */
protected final List resourceLoaders = new ArrayList();
/**
* This is a list of the template input stream source initializers, basically properties for a particular template stream
* source. The order in this list reflects numbering of the properties i.e.
*
* <p><loader-id>.resource.loader.<property> = <value></p>
*/
private final List sourceInitializerList = new ArrayList();
/**
* Has this Manager been initialized?
*/
private boolean isInit = false;
/** switch to turn off log notice when a resource is found for the first time. */
private boolean logWhenFound = true;
/** The internal RuntimeServices object. */
protected RuntimeServices rsvc = null;
/** Logging. */
protected Log log = null;
/**
* Initialize the ResourceManager.
*
* @param rsvc The Runtime Services object which is associated with this Resource Manager.
*
* @throws Exception
*/
public synchronized void initialize(final RuntimeServices rsvc)
throws Exception
{
if (isInit)
{
log.debug("Re-initialization of ResourceLoader attempted and ignored.");
return;
}
ResourceLoader resourceLoader = null;
this.rsvc = rsvc;
log = rsvc.getLog();
log.trace("Default ResourceManager initializing. (" + this.getClass() + ")");
assembleResourceLoaderInitializers();
for (Iterator it = sourceInitializerList.iterator(); it.hasNext();)
{
/**
* Resource loader can be loaded either via class name or be passed
* in as an instance.
*/
ExtendedProperties configuration = (ExtendedProperties) it.next();
String loaderClass = StringUtils.nullTrim(configuration.getString("class"));
ResourceLoader loaderInstance = (ResourceLoader) configuration.get("instance");
if (loaderInstance != null)
{
resourceLoader = loaderInstance;
}
else if (loaderClass != null)
{
resourceLoader = ResourceLoaderFactory.getLoader(rsvc, loaderClass);
}
else
{
String msg = "Unable to find '" +
configuration.getString(RESOURCE_LOADER_IDENTIFIER) +
".resource.loader.class' specification in configuration." +
" This is a critical value. Please adjust configuration.";
log.error(msg);
throw new Exception(msg);
}
resourceLoader.commonInit(rsvc, configuration);
resourceLoader.init(configuration);
resourceLoaders.add(resourceLoader);
}
/*
* now see if this is overridden by configuration
*/
logWhenFound = rsvc.getBoolean(RuntimeConstants.RESOURCE_MANAGER_LOGWHENFOUND, true);
/*
* now, is a global cache specified?
*/
String cacheClassName = rsvc.getString(RuntimeConstants.RESOURCE_MANAGER_CACHE_CLASS);
Object cacheObject = null;
if (org.apache.commons.lang.StringUtils.isNotEmpty(cacheClassName))
{
try
{
cacheObject = ClassUtils.getNewInstance(cacheClassName);
}
catch (ClassNotFoundException cnfe)
{
String msg = "The specified class for ResourceCache (" + cacheClassName +
") does not exist or is not accessible to the current classloader.";
log.error(msg, cnfe);
throw cnfe;
}
if (!(cacheObject instanceof ResourceCache))
{
String msg = "The specified resource cache class (" + cacheClassName +
") must implement " + ResourceCache.class.getName();
log.error(msg);
throw new RuntimeException(msg);
}
}
/*
* if we didn't get through that, just use the default.
*/
if (cacheObject == null)
{
cacheObject = new ResourceCacheImpl();
}
globalCache = (ResourceCache) cacheObject;
globalCache.initialize(rsvc);
log.trace("Default ResourceManager initialization complete.");
}
/**
* This will produce a List of Hashtables, each hashtable contains the intialization info for a particular resource loader. This
* Hashtable will be passed in when initializing the the template loader.
*/
private void assembleResourceLoaderInitializers()
{
Vector resourceLoaderNames = rsvc.getConfiguration().getVector(RuntimeConstants.RESOURCE_LOADER);
StringUtils.trimStrings(resourceLoaderNames);
for (Iterator it = resourceLoaderNames.iterator(); it.hasNext(); )
{
/*
* The loader id might look something like the following:
*
* file.resource.loader
*
* The loader id is the prefix used for all properties
* pertaining to a particular loader.
*/
String loaderName = (String) it.next();
StringBuffer loaderID = new StringBuffer(loaderName);
loaderID.append(".").append(RuntimeConstants.RESOURCE_LOADER);
ExtendedProperties loaderConfiguration =
rsvc.getConfiguration().subset(loaderID.toString());
/*
* we can't really count on ExtendedProperties to give us an empty set
*/
if (loaderConfiguration == null)
{
log.debug("ResourceManager : No configuration information found "+
"for resource loader named '" + loaderName +
"' (id is "+loaderID+"). Skipping it...");
continue;
}
/*
* add the loader name token to the initializer if we need it
* for reference later. We can't count on the user to fill
* in the 'name' field
*/
loaderConfiguration.setProperty(RESOURCE_LOADER_IDENTIFIER, loaderName);
/*
* Add resources to the list of resource loader
* initializers.
*/
sourceInitializerList.add(loaderConfiguration);
}
}
/**
* Gets the named resource. Returned class type corresponds to specified type (i.e. <code>Template</code> to <code>
* RESOURCE_TEMPLATE</code>).
*
* This method is now unsynchronized which requires that ResourceCache
* implementations be thread safe (as the default is).
*
* @param resourceName The name of the resource to retrieve.
* @param resourceType The type of resource (<code>RESOURCE_TEMPLATE</code>, <code>RESOURCE_CONTENT</code>, etc.).
* @param encoding The character encoding to use.
*
* @return Resource with the template parsed and ready.
*
* @throws ResourceNotFoundException if template not found from any available source.
* @throws ParseErrorException if template cannot be parsed due to syntax (or other) error.
* @throws Exception if a problem in parse
*/
public Resource getResource(final String resourceName, final int resourceType, final String encoding)
throws ResourceNotFoundException,
ParseErrorException,
Exception
{
/*
* Check to see if the resource was placed in the cache.
* If it was placed in the cache then we will use
* the cached version of the resource. If not we
* will load it.
*
* Note: the type is included in the key to differentiate ContentResource
* (static content from #include) with a Template.
*/
String resourceKey = resourceType + resourceName;
Resource resource = globalCache.get(resourceKey);
if (resource != null)
{
try
{
// avoids additional method call to refreshResource
if (resource.requiresChecking())
{
/*
* both loadResource() and refreshResource() now return
* a new Resource instance when they are called
* (put in the cache when appropriate) in order to allow
* several threads to parse the same template simultaneously.
* It is redundant work and will cause more garbage collection but the
* benefit is that it allows concurrent parsing and processing
* without race conditions when multiple requests try to
* refresh/load the same template at the same time.
*
* Another alternative is to limit template parsing/retrieval
* so that only one thread can parse each template at a time
* but that creates a scalability bottleneck.
*
* See VELOCITY-606, VELOCITY-595 and VELOCITY-24
*/
resource = refreshResource(resource, encoding);
}
}
catch (ResourceNotFoundException rnfe)
{
/*
* something exceptional happened to that resource
* this could be on purpose,
* so clear the cache and try again
*/
globalCache.remove(resourceKey);
return getResource(resourceName, resourceType, encoding);
}
catch (ParseErrorException pee)
{
log.error("ResourceManager.getResource() exception", pee);
throw pee;
}
catch (RuntimeException re)
{
log.error("ResourceManager.getResource() exception", re);
throw re;
}
catch (Exception e)
{
log.error("ResourceManager.getResource() exception", e);
throw e;
}
}
else
{
try
{
/*
* it's not in the cache, so load it.
*/
resource = loadResource(resourceName, resourceType, encoding);
if (resource.getResourceLoader().isCachingOn())
{
globalCache.put(resourceKey, resource);
}
}
catch (ResourceNotFoundException rnfe)
{
log.error("ResourceManager : unable to find resource '" +
resourceName + "' in any resource loader.");
throw rnfe;
}
catch (ParseErrorException pee)
{
log.error("ResourceManager.getResource() parse exception", pee);
throw pee;
}
catch (RuntimeException re)
{
log.error("ResourceManager.getResource() load exception", re);
throw re;
}
catch (Exception e)
{
log.error("ResourceManager.getResource() exception new", e);
throw e;
}
}
return resource;
}
/**
* Create a new Resource of the specified type.
*
* @param resourceName The name of the resource to retrieve.
* @param resourceType The type of resource (<code>RESOURCE_TEMPLATE</code>, <code>RESOURCE_CONTENT</code>, etc.).
* @return new instance of appropriate resource type
* @since 1.6
*/
protected Resource createResource(String resourceName, int resourceType)
{
return ResourceFactory.getResource(resourceName, resourceType);
}
/**
* Loads a resource from the current set of resource loaders.
*
* @param resourceName The name of the resource to retrieve.
* @param resourceType The type of resource (<code>RESOURCE_TEMPLATE</code>, <code>RESOURCE_CONTENT</code>, etc.).
* @param encoding The character encoding to use.
*
* @return Resource with the template parsed and ready.
*
* @throws ResourceNotFoundException if template not found from any available source.
* @throws ParseErrorException if template cannot be parsed due to syntax (or other) error.
* @throws Exception if a problem in parse
*/
protected Resource loadResource(String resourceName, int resourceType, String encoding)
throws ResourceNotFoundException,
ParseErrorException,
Exception
{
Resource resource = createResource(resourceName, resourceType);
resource.setRuntimeServices(rsvc);
resource.setName(resourceName);
resource.setEncoding(encoding);
/*
* Now we have to try to find the appropriate
* loader for this resource. We have to cycle through
* the list of available resource loaders and see
* which one gives us a stream that we can use to
* make a resource with.
*/
long howOldItWas = 0;
for (Iterator it = resourceLoaders.iterator(); it.hasNext();)
{
ResourceLoader resourceLoader = (ResourceLoader) it.next();
resource.setResourceLoader(resourceLoader);
/*
* catch the ResourceNotFound exception
* as that is ok in our new multi-loader environment
*/
try
{
if (resource.process())
{
/*
* FIXME (gmj)
* moved in here - technically still
* a problem - but the resource needs to be
* processed before the loader can figure
* it out due to to the new
* multi-path support - will revisit and fix
*/
if (logWhenFound && log.isDebugEnabled())
{
log.debug("ResourceManager : found " + resourceName +
" with loader " +
resourceLoader.getClassName());
}
howOldItWas = resourceLoader.getLastModified(resource);
break;
}
}
catch (ResourceNotFoundException rnfe)
{
/*
* that's ok - it's possible to fail in
* multi-loader environment
*/
}
}
/*
* Return null if we can't find a resource.
*/
if (resource.getData() == null)
{
throw new ResourceNotFoundException("Unable to find resource '" + resourceName + "'");
}
/*
* some final cleanup
*/
resource.setLastModified(howOldItWas);
resource.setModificationCheckInterval(resource.getResourceLoader().getModificationCheckInterval());
resource.touch();
return resource;
}
/**
* Takes an existing resource, and 'refreshes' it. This generally means that the source of the resource is checked for changes
* according to some cache/check algorithm and if the resource changed, then the resource data is reloaded and re-parsed.
*
* @param resource resource to refresh
* @param encoding character encoding of the resource to refresh.
*
* @throws ResourceNotFoundException if template not found from current source for this Resource
* @throws ParseErrorException if template cannot be parsed due to syntax (or other) error.
* @throws Exception if a problem in parse
*/
protected Resource refreshResource(Resource resource, final String encoding)
throws ResourceNotFoundException,
ParseErrorException,
Exception
{
/*
* The resource knows whether it needs to be checked
* or not, and the resource's loader can check to
* see if the source has been modified. If both
* these conditions are true then we must reload
* the input stream and parse it to make a new
* AST for the resource.
*/
/*
* touch() the resource to reset the counters
*/
resource.touch();
/* check whether this can now be found in a higher priority
* resource loader. if so, pass the request off to loadResource.
*/
ResourceLoader loader = resource.getResourceLoader();
if (resourceLoaders.size() > 0 && resourceLoaders.indexOf(loader) > 0)
{
String name = resource.getName();
if (loader != getLoaderForResource(name))
{
return loadResource(name, resource.getType(), encoding);
}
}
if (resource.isSourceModified())
{
/*
* now check encoding info. It's possible that the newly declared
* encoding is different than the encoding already in the resource
* this strikes me as bad...
*/
if (!org.apache.commons.lang.StringUtils.equals(resource.getEncoding(), encoding))
{
log.warn("Declared encoding for template '" +
resource.getName() +
"' is different on reload. Old = '" +
resource.getEncoding() + "' New = '" + encoding);
resource.setEncoding(encoding);
}
/*
* read how old the resource is _before_
* processing (=>reading) it
*/
long howOldItWas = loader.getLastModified(resource);
String resourceKey = resource.getType() + resource.getName();
/*
* we create a copy to avoid partially overwriting a
* template which may be in use in another thread
*/
Resource newResource =
ResourceFactory.getResource(resource.getName(), resource.getType());
newResource.setRuntimeServices(rsvc);
newResource.setName(resource.getName());
newResource.setEncoding(resource.getEncoding());
newResource.setResourceLoader(loader);
newResource.setModificationCheckInterval(loader.getModificationCheckInterval());
newResource.process();
newResource.setLastModified(howOldItWas);
resource = newResource;
globalCache.put(resourceKey, newResource);
}
return resource;
}
/**
* Gets the named resource. Returned class type corresponds to specified type (i.e. <code>Template</code> to <code>
* RESOURCE_TEMPLATE</code>).
*
* @param resourceName The name of the resource to retrieve.
* @param resourceType The type of resource (<code>RESOURCE_TEMPLATE</code>, <code>RESOURCE_CONTENT</code>, etc.).
*
* @return Resource with the template parsed and ready.
*
* @throws ResourceNotFoundException if template not found from any available source.
* @throws ParseErrorException if template cannot be parsed due to syntax (or other) error.
* @throws Exception if a problem in parse
*
* @deprecated Use {@link #getResource(String resourceName, int resourceType, String encoding )}
*/
public Resource getResource(String resourceName, int resourceType)
throws ResourceNotFoundException,
ParseErrorException,
Exception
{
return getResource(resourceName, resourceType, RuntimeConstants.ENCODING_DEFAULT);
}
/**
* Determines if a template exists, and returns name of the loader that provides it. This is a slightly less hokey way to
* support the Velocity.templateExists() utility method, which was broken when per-template encoding was introduced. We can
* revisit this.
*
* @param resourceName Name of template or content resource
*
* @return class name of loader than can provide it
*/
public String getLoaderNameForResource(String resourceName)
{
ResourceLoader loader = getLoaderForResource(resourceName);
if (loader == null)
{
return null;
}
return loader.getClass().toString();
}
/**
* Returns the first {@link ResourceLoader} in which the specified
* resource exists.
*/
private ResourceLoader getLoaderForResource(String resourceName)
{
for (Iterator i = resourceLoaders.iterator(); i.hasNext(); )
{
ResourceLoader loader = (ResourceLoader)i.next();
if (loader.resourceExists(resourceName))
{
return loader;
}
}
return null;
}
}
|