org.apache.velocity.servlet.VelocityServlet Maven / Gradle / Ivy
package org.apache.velocity.servlet;
/*
* 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.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.util.Properties;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.context.Context;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.io.VelocityWriter;
import org.apache.velocity.runtime.RuntimeConstants;
import org.apache.velocity.runtime.RuntimeSingleton;
import org.apache.velocity.util.SimplePool;
/**
* Base class which simplifies the use of Velocity with Servlets.
* Extend this class, implement the handleRequest() method,
* and add your data to the context. Then call
* getTemplate("myTemplate.wm").
*
* This class puts some things into the context object that you should
* be aware of:
*
* "req" - The HttpServletRequest object
* "res" - The HttpServletResponse object
*
*
* There are other methods you can override to access, alter or control
* any part of the request processing chain. Please see the javadocs for
* more information on :
*
* - loadConfiguration() : for setting up the Velocity runtime
*
- createContext() : for creating and loading the Context
*
- setContentType() : for changing the content type on a request
* by request basis
*
- handleRequest() : you must implement this
*
- mergeTemplate() : the template rendering process
*
- requestCleanup() : post rendering resource or other cleanup
*
- error() : error handling
*
*
* If you put a String with key "contentType" object into the context within either your
* servlet or within your template, then that will be used to override
* the default content type specified in the properties file.
*
* @deprecated This servlet has been replaced by VelocityViewServlet,
* available from the Velocity-Tools sub-project. VelocityViewServlet
* provides support for quick, clean MVC web development.
* VelocityServlet will be removed in a future version of Velocity.
*
* @author Dave Bryson
* @author Jon S. Stevens
* @author Geir Magnusson Jr.
* @author Kent Johnson
* @author Daniel Rall
* $Id: VelocityServlet.java 463298 2006-10-12 16:10:32Z henning $
*/
public abstract class VelocityServlet extends HttpServlet
{
/**
* The context key for the HTTP request object.
*/
public static final String REQUEST = "req";
/**
* The context key for the HTTP response object.
*/
public static final String RESPONSE = "res";
/**
* The HTTP content type context key.
*/
public static final String CONTENT_TYPE = "default.contentType";
/**
* The default content type for the response
*/
public static final String DEFAULT_CONTENT_TYPE = "text/html";
/**
* Encoding for the output stream
*/
public static final String DEFAULT_OUTPUT_ENCODING = "ISO-8859-1";
/**
* The default content type, itself defaulting to {@link
* #DEFAULT_CONTENT_TYPE} if not configured.
*/
private static String defaultContentType;
/**
* This is the string that is looked for when getInitParameter is
* called (org.apache.velocity.properties).
*/
protected static final String INIT_PROPS_KEY =
"org.apache.velocity.properties";
/**
* Use of this properties key has been deprecated, and will be
* removed in Velocity version 1.5.
*/
private static final String OLD_INIT_PROPS_KEY = "properties";
/**
* Cache of writers
*/
private static SimplePool writerPool = new SimplePool(40);
/**
* Performs initialization of this servlet. Called by the servlet
* container on loading.
*
* @param config The servlet configuration to apply.
*
* @exception ServletException
*/
public void init( ServletConfig config )
throws ServletException
{
super.init( config );
/*
* do whatever we have to do to init Velocity
*/
initVelocity( config );
/*
* Now that Velocity is initialized, cache some config.
*/
VelocityServlet.defaultContentType =
RuntimeSingleton.getString(CONTENT_TYPE, DEFAULT_CONTENT_TYPE);
}
/**
* Initializes the Velocity runtime, first calling
* loadConfiguration(ServletConvig) to get a
* java.util.Properties of configuration information
* and then calling Velocity.init(). Override this
* to do anything to the environment before the
* initialization of the singelton takes place, or to
* initialize the singleton in other ways.
* @param config
* @throws ServletException
*/
protected void initVelocity( ServletConfig config )
throws ServletException
{
try
{
/*
* call the overridable method to allow the
* derived classes a shot at altering the configuration
* before initializing Runtime
*/
Properties props = loadConfiguration( config );
Velocity.init( props );
}
catch( Exception e )
{
throw new ServletException("Error initializing Velocity: " + e, e);
}
}
/**
* Loads the configuration information and returns that
* information as a Properties, which will be used to
* initialize the Velocity runtime.
*
* Currently, this method gets the initialization parameter
* VelocityServlet.INIT_PROPS_KEY, which should be a file containing
* the configuration information.
*
* To configure your Servlet Spec 2.2 compliant servlet runner to pass
* this to you, put the following in your WEB-INF/web.xml file
*
*
* <servlet>
* <servlet-name> YourServlet </servlet-name>
* <servlet-class> your.package.YourServlet </servlet-class>
* <init-param>
* <param-name> org.apache.velocity.properties </param-name>
* <param-value> velocity.properties </param-value>
* </init-param>
* </servlet>
*
*
* Alternately, if you wish to configure an entire context in this
* fashion, you may use the following:
*
*
* <context-param>
* <param-name> org.apache.velocity.properties </param-name>
* <param-value> velocity.properties </param-value>
* <description> Path to Velocity configuration </description>
* </context-param>
*
*
* Derived classes may do the same, or take advantage of this code to do the loading for them via :
*
* Properties p = super.loadConfiguration( config );
*
* and then add or modify the configuration values from the file.
*
*
* @param config ServletConfig passed to the servlets init() function
* Can be used to access the real path via ServletContext (hint)
* @return java.util.Properties loaded with configuration values to be used
* to initialize the Velocity runtime.
* @throws FileNotFoundException if a specified file is not found.
* @throws IOException I/O problem accessing the specified file, if specified.
* @deprecated Use VelocityViewServlet from the Velocity Tools
* library instead.
*/
protected Properties loadConfiguration(ServletConfig config)
throws IOException, FileNotFoundException
{
// This is a little overly complex because of legacy support
// for the initialization properties key "properties".
// References to OLD_INIT_PROPS_KEY should be removed at
// Velocity version 1.5.
String propsFile = config.getInitParameter(INIT_PROPS_KEY);
if (propsFile == null || propsFile.length() == 0)
{
ServletContext sc = config.getServletContext();
propsFile = config.getInitParameter(OLD_INIT_PROPS_KEY);
if (propsFile == null || propsFile.length() == 0)
{
propsFile = sc.getInitParameter(INIT_PROPS_KEY);
if (propsFile == null || propsFile.length() == 0)
{
propsFile = sc.getInitParameter(OLD_INIT_PROPS_KEY);
if (propsFile != null && propsFile.length() > 0)
{
sc.log("Use of the properties initialization " +
"parameter '" + OLD_INIT_PROPS_KEY + "' has " +
"been deprecated by '" + INIT_PROPS_KEY + '\'');
}
}
}
else
{
sc.log("Use of the properties initialization parameter '" +
OLD_INIT_PROPS_KEY + "' has been deprecated by '" +
INIT_PROPS_KEY + '\'');
}
}
/*
* This will attempt to find the location of the properties
* file from the relative path to the WAR archive (ie:
* docroot). Since JServ returns null for getRealPath()
* because it was never implemented correctly, then we know we
* will not have an issue with using it this way. I don't know
* if this will break other servlet engines, but it probably
* shouldn't since WAR files are the future anyways.
*/
Properties p = new Properties();
if ( propsFile != null )
{
p.load(getServletContext().getResourceAsStream(propsFile));
}
return p;
}
/**
* Handles HTTP GET requests by calling {@link
* #doRequest(HttpServletRequest, HttpServletResponse)}.
* @param request
* @param response
* @throws ServletException
* @throws IOException
*/
public void doGet( HttpServletRequest request, HttpServletResponse response )
throws ServletException, IOException
{
doRequest(request, response);
}
/**
* Handles HTTP POST requests by calling {@link
* #doRequest(HttpServletRequest, HttpServletResponse)}.
* @param request
* @param response
* @throws ServletException
* @throws IOException
*/
public void doPost( HttpServletRequest request, HttpServletResponse response )
throws ServletException, IOException
{
doRequest(request, response);
}
/**
* Handles all requests (by default).
*
* @param request HttpServletRequest object containing client request
* @param response HttpServletResponse object for the response
* @throws ServletException
* @throws IOException
*/
protected void doRequest(HttpServletRequest request, HttpServletResponse response )
throws ServletException, IOException
{
Context context = null;
try
{
/*
* first, get a context
*/
context = createContext( request, response );
/*
* set the content type
*/
setContentType( request, response );
/*
* let someone handle the request
*/
Template template = handleRequest( request, response, context );
/*
* bail if we can't find the template
*/
if ( template == null )
{
return;
}
/*
* now merge it
*/
mergeTemplate( template, context, response );
}
catch (Exception e)
{
/*
* call the error handler to let the derived class
* do something useful with this failure.
*/
error( request, response, e);
}
finally
{
/*
* call cleanup routine to let a derived class do some cleanup
*/
requestCleanup( request, response, context );
}
}
/**
* A cleanup routine which is called at the end of the {@link
* #doRequest(HttpServletRequest, HttpServletResponse)}
* processing sequence, allowing a derived class to do resource
* cleanup or other end of process cycle tasks.
*
* @param request servlet request from client
* @param response servlet reponse
* @param context context created by the createContext() method
*/
protected void requestCleanup( HttpServletRequest request, HttpServletResponse response, Context context )
{
}
/**
* merges the template with the context. Only override this if you really, really
* really need to. (And don't call us with questions if it breaks :)
*
* @param template template object returned by the handleRequest() method
* @param context context created by the createContext() method
* @param response servlet reponse (use this to get the output stream or Writer
* @throws ResourceNotFoundException
* @throws ParseErrorException
* @throws MethodInvocationException
* @throws IOException
* @throws UnsupportedEncodingException
* @throws Exception
*/
protected void mergeTemplate( Template template, Context context, HttpServletResponse response )
throws ResourceNotFoundException, ParseErrorException,
MethodInvocationException, IOException, UnsupportedEncodingException, Exception
{
ServletOutputStream output = response.getOutputStream();
VelocityWriter vw = null;
// ASSUMPTION: response.setContentType() has been called.
String encoding = response.getCharacterEncoding();
try
{
vw = (VelocityWriter) writerPool.get();
if (vw == null)
{
vw = new VelocityWriter(new OutputStreamWriter(output,
encoding),
4 * 1024, true);
}
else
{
vw.recycle(new OutputStreamWriter(output, encoding));
}
template.merge(context, vw);
}
finally
{
if (vw != null)
{
try
{
/*
* flush and put back into the pool
* don't close to allow us to play
* nicely with others.
*/
vw.flush();
}
catch (IOException e)
{
// do nothing
}
/*
* Clear the VelocityWriter's reference to its
* internal OutputStreamWriter to allow the latter
* to be GC'd while vw is pooled.
*/
vw.recycle(null);
writerPool.put(vw);
}
}
}
/**
* Sets the content type of the response, defaulting to {@link
* #defaultContentType} if not overriden. Delegates to {@link
* #chooseCharacterEncoding(HttpServletRequest)} to select the
* appropriate character encoding.
*
* @param request The servlet request from the client.
* @param response The servlet reponse to the client.
*/
protected void setContentType(HttpServletRequest request,
HttpServletResponse response)
{
String contentType = VelocityServlet.defaultContentType;
int index = contentType.lastIndexOf(';') + 1;
if (index <= 0 || (index < contentType.length() &&
contentType.indexOf("charset", index) == -1))
{
// Append the character encoding which we'd like to use.
String encoding = chooseCharacterEncoding(request);
//RuntimeSingleton.debug("Chose output encoding of '" +
// encoding + '\'');
if (!DEFAULT_OUTPUT_ENCODING.equalsIgnoreCase(encoding))
{
contentType += "; charset=" + encoding;
}
}
response.setContentType(contentType);
//RuntimeSingleton.debug("Response Content-Type set to '" +
// contentType + '\'');
}
/**
* Chooses the output character encoding to be used as the value
* for the "charset=" portion of the HTTP Content-Type header (and
* thus returned by response.getCharacterEncoding()).
* Called by {@link #setContentType(HttpServletRequest,
* HttpServletResponse)} if an encoding isn't already specified by
* Content-Type. By default, chooses the value of
* RuntimeSingleton's output.encoding property.
*
* @param request The servlet request from the client.
* @return The chosen character encoding.
*/
protected String chooseCharacterEncoding(HttpServletRequest request)
{
return RuntimeSingleton.getString(RuntimeConstants.OUTPUT_ENCODING,
DEFAULT_OUTPUT_ENCODING);
}
/**
* Returns a context suitable to pass to the handleRequest() method
*
* Default implementation will create a VelocityContext object,
* put the HttpServletRequest and HttpServletResponse
* into the context accessable via the keys VelocityServlet.REQUEST and
* VelocityServlet.RESPONSE, respectively.
*
* @param request servlet request from client
* @param response servlet reponse to client
*
* @return context
*/
protected Context createContext(HttpServletRequest request, HttpServletResponse response )
{
/*
* create a new context
*/
VelocityContext context = new VelocityContext();
/*
* put the request/response objects into the context
* wrap the HttpServletRequest to solve the introspection
* problems
*/
context.put( REQUEST, request );
context.put( RESPONSE, response );
return context;
}
/**
* Retrieves the requested template.
*
* @param name The file name of the template to retrieve relative to the
* template root.
* @return The requested template.
* @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 an error occurs in template initialization
*/
public Template getTemplate( String name )
throws ResourceNotFoundException, ParseErrorException, Exception
{
return RuntimeSingleton.getTemplate(name);
}
/**
* Retrieves the requested template with the specified
* character encoding.
*
* @param name The file name of the template to retrieve relative to the
* template root.
* @param encoding the character encoding of the template
*
* @return The requested template.
* @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 an error occurs in template initialization
*
* @since Velocity v1.1
*/
public Template getTemplate( String name, String encoding )
throws ResourceNotFoundException, ParseErrorException, Exception
{
return RuntimeSingleton.getTemplate( name, encoding );
}
/**
* Implement this method to add your application data to the context,
* calling the getTemplate() method to produce your return
* value.
*
* In the event of a problem, you may handle the request directly
* and return null or throw a more meaningful exception
* for the error handler to catch.
*
* @param request servlet request from client
* @param response servlet reponse
* @param ctx The context to add your data to.
* @return The template to merge with your context or null, indicating
* that you handled the processing.
* @throws Exception
*
* @since Velocity v1.1
*/
protected Template handleRequest( HttpServletRequest request, HttpServletResponse response, Context ctx )
throws Exception
{
/*
* invoke handleRequest
*/
Template t = handleRequest( ctx );
/*
* if it returns null, this is the 'old' deprecated
* way, and we want to mimic the behavior for a little
* while anyway
*/
if (t == null)
{
throw new Exception ("handleRequest(Context) returned null - no template selected!" );
}
return t;
}
/**
* Implement this method to add your application data to the context,
* calling the getTemplate() method to produce your return
* value.
*
* In the event of a problem, you may simple return null
* or throw a more meaningful exception.
*
* @deprecated Use
* {@link #handleRequest( HttpServletRequest request,
* HttpServletResponse response, Context ctx )}
*
* @param ctx The context to add your data to.
* @return The template to merge with your context.
* @throws Exception
*/
protected Template handleRequest( Context ctx )
throws Exception
{
throw new Exception ("You must override VelocityServlet.handleRequest( Context) "
+ " or VelocityServlet.handleRequest( HttpServletRequest, "
+ " HttpServletResponse, Context)" );
}
/**
* Invoked when there is an error thrown in any part of doRequest() processing.
*
* Default will send a simple HTML response indicating there was a problem.
*
* @param request original HttpServletRequest from servlet container.
* @param response HttpServletResponse object from servlet container.
* @param cause Exception that was thrown by some other part of process.
* @throws ServletException
* @throws IOException
*/
protected void error( HttpServletRequest request, HttpServletResponse response, Exception cause )
throws ServletException, IOException
{
StringBuffer html = new StringBuffer();
html.append("");
html.append("Error ");
html.append("");
html.append("VelocityServlet: Error processing the template
");
html.append("");
String why = cause.getMessage();
if (why != null && why.trim().length() > 0)
{
html.append(why);
html.append("
");
}
StringWriter sw = new StringWriter();
cause.printStackTrace( new PrintWriter( sw ) );
html.append( sw.toString() );
html.append("");
html.append("");
html.append("");
response.getOutputStream().print( html.toString() );
}
}
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