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//
// $Id$
//
// samskivert library - useful routines for java programs
// Copyright (C) 2001-2011 Michael Bayne, et al.
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation; either version 2.1 of the License, or
// (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package com.samskivert.velocity;
import java.util.Locale;
import java.util.Properties;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import org.apache.velocity.app.Velocity;
import com.samskivert.servlet.HttpErrorException;
import com.samskivert.servlet.IndiscriminateSiteIdentifier;
import com.samskivert.servlet.MessageManager;
import com.samskivert.servlet.RedirectException;
import com.samskivert.servlet.SiteIdentifier;
import com.samskivert.servlet.SiteResourceLoader;
import com.samskivert.servlet.util.ExceptionMap;
import com.samskivert.servlet.util.FriendlyException;
import com.samskivert.servlet.util.RequestUtils;
import com.samskivert.util.StringUtil;
import static com.samskivert.Log.log;
/**
* The servlet API defines the concept of a web application and associates certain attributes with
* it like document root and so on. This application class extends that concept by providing a base
* class that represents the web application. The application class is responsible for initializing
* services that will be used by the application's logic objects as well as cleaning them up when
* the application is shut down.
*
* Error handling
* The application provides a common error handling mechanism. The design is to catch any
* exceptions thrown by the logic and to convert them into friendly error messages that are
* inserted into the invocation context with the key "error" for easy display in the
* resulting web page.
*
*
The default process of mapping exceptions to friendly error messages is done using the
* {@link ExceptionMap} class. This can be replaced by overriding {@link #handleException}.
*/
public class Application
{
/**
* An initialized application automatically registers itself as a Velocity application
* attribute so that it can be retrieved by Velocity plugins using
* getApplicationAttribute(VELOCITY_ATTR_KEY).
*/
public static final String VELOCITY_ATTR_KEY = "!application!";
/**
* Performs initializations common to all applications. Applications should override {@link
* #willInit} to perform initializations that need to take place before the common
* initialization (which includes the creation of the site identifier and message manager) and
* should override {@link #didInit} to perform initializations that need to take place after
* the common initialization (like passing the application to entities that might turn around
* and request a reference to our site identifier).
*
* @param config the servlet config from which the application will load configuration
* information.
* @param context the servlet context in which this application is operating.
* @param logicPkg the base package for all of the logic implementations for this application.
*/
public void init (ServletConfig config, ServletContext context, String logicPkg)
{
// keep this around for later
_context = context;
// stick ourselves into an application attribute so that we can be accessed by Velocity
// plugins
Velocity.setApplicationAttribute(VELOCITY_ATTR_KEY, this);
// let the derived application do pre-init stuff
willInit(config);
// remove any trailing dot
if (logicPkg.endsWith(".")) {
_logicPkg = logicPkg.substring(0, logicPkg.length()-1);
} else {
_logicPkg = logicPkg;
}
// create our site identifier
_siteIdent = createSiteIdentifier(_context);
// create a site resource loader if the user set up the site-specific jar file path
String siteJarPath = getInitParameter(config, SITE_JAR_PATH_KEY);
if (!StringUtil.isBlank(siteJarPath)) {
_siteLoader = new SiteResourceLoader(_siteIdent, siteJarPath);
}
// instantiate our message manager if the application wants one
String bundlePath = getInitParameter(config, MESSAGE_BUNDLE_PATH_KEY);
if (!StringUtil.isBlank(bundlePath)) {
_msgmgr = createMessageManager(bundlePath);
}
// if we have a site-specific resource loader, configure the message manager with it, so
// that it can load site-specific message resources
if (_msgmgr != null && _siteLoader != null) {
String siteBundlePath = getInitParameter(config, SITE_MESSAGE_BUNDLE_PATH_KEY);
if (!StringUtil.isBlank(siteBundlePath)) {
_msgmgr.activateSiteSpecificMessages(siteBundlePath, _siteLoader);
} else {
log.info("No '" + SITE_MESSAGE_BUNDLE_PATH_KEY + "' specified in servlet " +
"configuration. This is required to allow the message manager to load " +
"site-specific translation resources.");
}
}
// let the derived application do post-init stuff
didInit(config);
}
/**
* Called prior to initializing Velocity to allow the application to specify custom
* configuration properties.
*/
protected void configureVelocity (ServletConfig config, Properties props)
{
}
/**
* Looks up an initialization parameter for this application. The default implementation
* retrieves the value from the servlet config, but derived classes may wish to get certain
* parameters from some other configuration source.
*/
protected String getInitParameter (ServletConfig config, String key)
{
return config.getInitParameter(key);
}
/**
* Creates the message manager to be used for this application.
*/
protected MessageManager createMessageManager (String bundlePath)
{
return new MessageManager(bundlePath, Locale.getDefault(), _siteIdent);
}
/**
* This should be overridden by the application implementation to invoke any necessary
* pre-initialization code. They should be sure to call super.willInit().
*/
protected void willInit (ServletConfig config)
{
}
/**
* This should be overridden by the application implementation to invoke any necessary
* post-initialization code. They should be sure to call super.didInit().
*/
protected void didInit (ServletConfig config)
{
}
/**
* Allows derived aplication classes to prepare an invocation context prior to the logic class
* being invoked. They may wish to add standard tools to the context or do any other
* request-invariant preparation.
*/
protected void prepareContext (InvocationContext ctx)
{
}
/**
* Allows derived application classes to check access in a single location prior to resolving
* and dispatching a logic class, if they desire access control at this level. Alternatively,
* access control can be performed by the logic instance.
*/
protected void checkAccess (InvocationContext ctx)
throws RedirectException, HttpErrorException
{
}
/**
* If an exception propagates up from {@link Logic#invoke}, the application is given the chance
* to convert a low-level exception into a {@link FriendlyException} or a {@link
* RedirectException} which will be handled in the normal way.
*/
protected Exception translateException (Exception error)
{
return error;
}
/**
* If a generic exception propagates up from {@link Logic#invoke} and is not otherwise
* converted into a friendly or redirect exception, the application will be required to provide
* a generic error message to be inserted into the context and should take this opportunity to
* log the exception.
*
*
Note: the string returned by this method will be translated using the
* application's message manager before being inserted into the Velocity context.
*/
protected String handleException (HttpServletRequest req, Logic logic, Exception error)
{
log.warning(logic + " failed on: " + RequestUtils.reconstructURL(req), error);
return ExceptionMap.getMessage(error);
}
/**
* This should be overridden by the application implementation to perform any necessary
* cleanup.
*/
public void shutdown ()
{
}
/**
* Returns a reference to the servlet context in which this application is operating.
*/
public ServletContext getServletContext ()
{
return _context;
}
/**
* Returns the message manager in effect for this application, if one is in effect.
*/
public MessageManager getMessageManager ()
{
return _msgmgr;
}
/**
* Returns the site identifier in effect for figuring out which site through which a user is
* making a request.
*/
public SiteIdentifier getSiteIdentifier ()
{
return _siteIdent;
}
/**
* Returns a reference to the loader used to obtain site-specific resources. This is only valid
* if the user specified the site-specific jar file path in the servlet configuration.
*
* @see #SITE_JAR_PATH_KEY
*/
public SiteResourceLoader getSiteResourceLoader ()
{
return _siteLoader;
}
/**
* Called to instantiate the site identifier that we'd like to use in this application. This
* will be an instance of {@link IndiscriminateSiteIdentifier} unless the derived application
* class overrides this method and creates something more to its liking. This will be called
* after the application's {@link #init} method has been called.
*/
protected SiteIdentifier createSiteIdentifier (ServletContext ctx)
{
return new IndiscriminateSiteIdentifier();
}
/**
* A convenience function for translating messages.
*/
public final String translate (InvocationContext ctx, String msg)
{
return _msgmgr.getMessage(ctx.getRequest(), msg);
}
/**
* A convenience function for translating messages.
*/
public final String translate (InvocationContext ctx, String msg, Object... args)
{
return _msgmgr.getMessage(ctx.getRequest(), msg, args);
}
/**
* Given the servlet path (the part of the URI after the context path) this generates the
* classname of the logic class that should handle the request.
*/
protected String generateClass (String path)
{
// remove the trailing file extension
int ldidx = path.lastIndexOf(".");
if (ldidx != -1) {
path = path.substring(0, ldidx);
}
// convert slashes to dots
path = path.replace('/', '.');
// prepend the base logic package and we're all set
return _logicPkg + path;
}
/** A reference to the servlet context in which this application is operating. */
protected ServletContext _context;
/** The prefix that we use to generate fully qualified logic class names. */
protected String _logicPkg;
/** A reference to our message manager or null if we have none. */
protected MessageManager _msgmgr;
/** A reference to our site identifier. */
protected SiteIdentifier _siteIdent;
/** Provides access to site-specific resources. */
protected SiteResourceLoader _siteLoader;
/** The servlet parameter key specifying the path to the application's translated message
* resources. */
protected static final String MESSAGE_BUNDLE_PATH_KEY = "messages_path";
/** The servlet parameter key specifying the path to the site-specific jar files. */
protected static final String SITE_JAR_PATH_KEY = "site_jar_path";
/** The servlet parameter key specifying the path to the site-specific translated message
* resources. */
protected static final String SITE_MESSAGE_BUNDLE_PATH_KEY = "site_messages_path";
}