org.apache.velocity.tools.view.servlet
Class VelocityViewServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          org.apache.velocity.tools.view.servlet.VelocityViewServlet

All Implemented Interfaces:

java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

Direct Known Subclasses:

VelocityLayoutServlet

public class VelocityViewServlet
extends javax.servlet.http.HttpServlet

A servlet to process Velocity templates. This is comparable to the the JspServlet for JSP-based applications.

The servlet provides the following features:

• renders Velocity templates
• provides support for an auto-loaded, configurable toolbox
• provides transparent access to the servlet request attributes, servlet session attributes and servlet context attributes by auto-searching them
• logs to the logging facility of the servlet API

VelocityViewServlet supports the following configuration parameters in web.xml:

org.apache.velocity.toolbox

Path and name of the toolbox configuration file. The path must be relative to the web application root directory. If this parameter is not found, the servlet will check for a toolbox file at '/WEB-INF/toolbox.xml'.

org.apache.velocity.properties

Path and name of the Velocity configuration file. The path must be relative to the web application root directory. If this parameter is not present, Velocity will check for a properties file at '/WEB-INF/velocity.properties'. If no file is found there, then Velocity is initialized with the settings in the classpath at 'org.apache.velocity.tools.view.servlet.velocity.properties'.

There are methods you may wish to override to access, alter or control any part of the request processing chain. Please see the javadocs for more information on :

• loadConfiguration(javax.servlet.ServletConfig) :
  for loading Velocity properties and configuring the Velocity runtime
• setContentType(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse) :
  for changing the content type on a request by request basis
• fillContext(org.apache.velocity.context.Context, javax.servlet.http.HttpServletRequest) :
  for add data to the context before template rendering
• requestCleanup(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, org.apache.velocity.context.Context) :
  post rendering resource or other cleanup
• error(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, java.lang.Exception) :
  error handling

Version:

$Id: VelocityViewServlet.java 595092 2007-11-14 22:15:13Z nbubna $

Author:

Dave Bryson, Jon S. Stevens, Gabe Sidler, Geir Magnusson Jr., Kent Johnson, Daniel Rall, Nathan Bubna

See Also:

Serialized Form

Field Summary

static java.lang.String	CONTENT_TYPE The HTTP content type context key.
static java.lang.String	DEFAULT_CONTENT_TYPE The default content type for the response
static java.lang.String	DEFAULT_OUTPUT_ENCODING Default encoding for the output stream
protected static java.lang.String	DEFAULT_PROPERTIES_PATH Default velocity properties file path.
protected static java.lang.String	DEFAULT_TOOLBOX_PATH Default toolbox configuration file path.
static java.lang.String	DEFAULT_TOOLS_PROPERTIES Default Runtime properties.
private java.lang.String	defaultContentType The default content type.
protected static java.lang.String	INIT_PROPS_KEY This is the string that is looked for when getInitParameter is called ("org.apache.velocity.properties").
private static long	serialVersionUID serial version id
static java.lang.String	SERVLET_CONTEXT_KEY Key used to access the ServletContext in the Velocity application attributes.
protected static java.lang.String	TOOLBOX_KEY Key used to access the toolbox configuration file path from the Servlet or webapp init parameters ("org.apache.velocity.toolbox").
protected ToolboxManager	toolboxManager A reference to the toolbox manager.
private org.apache.velocity.app.VelocityEngine	velocity
private boolean	warnOfOutputStreamDeprecation Whether we've logged a deprecation warning for ServletResponse's getOutputStream().
private static org.apache.velocity.util.SimplePool	writerPool Cache of writers

Constructor Summary

VelocityViewServlet()

Method Summary

protected org.apache.velocity.context.Context	createContext(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Creates and returns an initialized Velocity context.
void	doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Handles GET - calls doRequest()
void	doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Handle a POST request - calls doRequest()
protected void	doRequest(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Handles with both GET and POST requests
protected void	error(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, java.lang.Exception e) Invoked when there is an error thrown in any part of doRequest() processing.
protected void	fillContext(org.apache.velocity.context.Context context, javax.servlet.http.HttpServletRequest request) This is an extension hook for users who subclass this servlet to make their own modifications to the Context.
protected java.lang.String	findInitParameter(javax.servlet.ServletConfig config, java.lang.String key) Looks up an init parameter with the specified key in either the ServletConfig or, failing that, in the ServletContext.
protected java.io.Writer	getResponseWriter(javax.servlet.http.HttpServletResponse response) Procure a Writer with correct encoding which can be used even if HttpServletResponse's getOutputStream() method has already been called.
protected org.apache.velocity.Template	getTemplate(javax.servlet.http.HttpServletRequest request) Gets the requested template.
protected org.apache.velocity.Template	getTemplate(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Gets the requested template.
org.apache.velocity.Template	getTemplate(java.lang.String name) Retrieves the requested template.
org.apache.velocity.Template	getTemplate(java.lang.String name, java.lang.String encoding) Retrieves the requested template with the specified character encoding.
protected org.apache.velocity.app.VelocityEngine	getVelocityEngine() Returns the underlying VelocityEngine being used.
protected java.lang.String	getVelocityProperty(java.lang.String key, java.lang.String alternate) Simplifies process of getting a property from VelocityEngine, because the VelocityEngine interface sucks compared to the singleton's.
protected org.apache.velocity.Template	handleRequest(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, org.apache.velocity.context.Context ctx) Deprecated. This will be removed in VelocityTools 2.0.
void	init(javax.servlet.ServletConfig config) Initializes servlet, toolbox and Velocity template engine.
protected void	initToolbox(javax.servlet.ServletConfig config) Initializes the ServletToolboxManager for this servlet's toolbox (if any).
protected void	initVelocity(javax.servlet.ServletConfig config) Initializes the Velocity runtime, first calling loadConfiguration(ServletConfig) to get a org.apache.commons.collections.ExtendedProperties of configuration information and then calling velocityEngine.init().
protected org.apache.commons.collections.ExtendedProperties	loadConfiguration(javax.servlet.ServletConfig config) Loads the configuration information and returns that information as an ExtendedProperties, which will be used to initialize the Velocity runtime.
private org.apache.commons.collections.ExtendedProperties	loadDefaultProperties()
protected void	mergeTemplate(org.apache.velocity.Template template, org.apache.velocity.context.Context context, javax.servlet.http.HttpServletResponse response) Merges the template with the context.
protected void	performMerge(org.apache.velocity.Template template, org.apache.velocity.context.Context context, java.io.Writer writer) This is here so developers may override it and gain access to the Writer which the template will be merged into.
protected void	requestCleanup(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, org.apache.velocity.context.Context context) Cleanup routine called at the end of the request processing sequence allows a derived class to do resource cleanup or other end of process cycle tasks.
protected void	setContentType(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Sets the content type of the response.
protected void	setVelocityEngine(org.apache.velocity.app.VelocityEngine ve) Sets the underlying VelocityEngine

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

serialVersionUID

private static final long serialVersionUID

serial version id

See Also:

Constant Field Values

CONTENT_TYPE

public static final java.lang.String CONTENT_TYPE

The HTTP content type context key.

See Also:

Constant Field Values

DEFAULT_CONTENT_TYPE

public static final java.lang.String DEFAULT_CONTENT_TYPE

The default content type for the response

See Also:

Constant Field Values

DEFAULT_OUTPUT_ENCODING

public static final java.lang.String DEFAULT_OUTPUT_ENCODING

Default encoding for the output stream

See Also:

Constant Field Values

SERVLET_CONTEXT_KEY

public static final java.lang.String SERVLET_CONTEXT_KEY

Key used to access the ServletContext in the Velocity application attributes.

DEFAULT_TOOLS_PROPERTIES

public static final java.lang.String DEFAULT_TOOLS_PROPERTIES

Default Runtime properties.

See Also:

Constant Field Values

TOOLBOX_KEY

protected static final java.lang.String TOOLBOX_KEY

Key used to access the toolbox configuration file path from the Servlet or webapp init parameters ("org.apache.velocity.toolbox").

See Also:

Constant Field Values

INIT_PROPS_KEY

protected static final java.lang.String INIT_PROPS_KEY

This is the string that is looked for when getInitParameter is called ("org.apache.velocity.properties").

See Also:

Constant Field Values

DEFAULT_TOOLBOX_PATH

protected static final java.lang.String DEFAULT_TOOLBOX_PATH

Default toolbox configuration file path. If no alternate value for this is specified, the servlet will look here.

See Also:

Constant Field Values

DEFAULT_PROPERTIES_PATH

protected static final java.lang.String DEFAULT_PROPERTIES_PATH

Default velocity properties file path. If no alternate value for this is specified, the servlet will look here.

See Also:

Constant Field Values

toolboxManager

protected ToolboxManager toolboxManager

A reference to the toolbox manager.

writerPool

private static org.apache.velocity.util.SimplePool writerPool

Cache of writers

velocity

private org.apache.velocity.app.VelocityEngine velocity

defaultContentType

private java.lang.String defaultContentType

The default content type. When necessary, includes the character set to use when encoding textual output.

warnOfOutputStreamDeprecation

private boolean warnOfOutputStreamDeprecation

Whether we've logged a deprecation warning for ServletResponse's getOutputStream().

Since:

VelocityTools 1.1

Constructor Detail

VelocityViewServlet

public VelocityViewServlet()

Method Detail

init

public void init(javax.servlet.ServletConfig config)
          throws javax.servlet.ServletException

Initializes servlet, toolbox and Velocity template engine. Called by the servlet container on loading.

NOTE: If no charset is specified in the default.contentType property (in your velocity.properties) and you have specified an output.encoding property, then that will be used as the charset for the default content-type of pages served by this servlet.

Specified by:

init in interface javax.servlet.Servlet

Overrides:

init in class javax.servlet.GenericServlet

Parameters:

config - servlet configuation

Throws:

javax.servlet.ServletException

findInitParameter

protected java.lang.String findInitParameter(javax.servlet.ServletConfig config,
                                             java.lang.String key)

Looks up an init parameter with the specified key in either the ServletConfig or, failing that, in the ServletContext.

getVelocityProperty

protected java.lang.String getVelocityProperty(java.lang.String key,
                                               java.lang.String alternate)

Simplifies process of getting a property from VelocityEngine, because the VelocityEngine interface sucks compared to the singleton's. Use of this method assumes that initVelocity(ServletConfig) has already been called.

getVelocityEngine

protected org.apache.velocity.app.VelocityEngine getVelocityEngine()

Returns the underlying VelocityEngine being used.

setVelocityEngine

protected void setVelocityEngine(org.apache.velocity.app.VelocityEngine ve)

Sets the underlying VelocityEngine

initToolbox

protected void initToolbox(javax.servlet.ServletConfig config)
                    throws javax.servlet.ServletException

Initializes the ServletToolboxManager for this servlet's toolbox (if any).

Parameters:

config - servlet configuation

Throws:

javax.servlet.ServletException

initVelocity

protected void initVelocity(javax.servlet.ServletConfig config)
                     throws javax.servlet.ServletException

Initializes the Velocity runtime, first calling loadConfiguration(ServletConfig) to get a org.apache.commons.collections.ExtendedProperties of configuration information and then calling velocityEngine.init(). Override this to do anything to the environment before the initialization of the singleton takes place, or to initialize the singleton in other ways.

Parameters:

config - servlet configuration parameters

Throws:

javax.servlet.ServletException

loadDefaultProperties

private org.apache.commons.collections.ExtendedProperties loadDefaultProperties()

loadConfiguration

protected org.apache.commons.collections.ExtendedProperties loadConfiguration(javax.servlet.ServletConfig config)
                                                                       throws java.io.IOException

Loads the configuration information and returns that information as an ExtendedProperties, 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 :

      ExtendedProperties p = super.loadConfiguration(config);
   

and then add or modify the configuration values from the file.

Parameters:

config - ServletConfig passed to the servlets init() function Can be used to access the real path via ServletContext (hint)

Returns:

ExtendedProperties loaded with configuration values to be used to initialize the Velocity runtime.

Throws:

java.io.IOException - I/O problem accessing the specified file, if specified.

doGet

public void doGet(javax.servlet.http.HttpServletRequest request,
                  javax.servlet.http.HttpServletResponse response)
           throws javax.servlet.ServletException,
                  java.io.IOException

Handles GET - calls doRequest()

Overrides:

doGet in class javax.servlet.http.HttpServlet

Throws:

javax.servlet.ServletException

java.io.IOException

doPost

public void doPost(javax.servlet.http.HttpServletRequest request,
                   javax.servlet.http.HttpServletResponse response)
            throws javax.servlet.ServletException,
                   java.io.IOException

Handle a POST request - calls doRequest()

Overrides:

doPost in class javax.servlet.http.HttpServlet

Throws:

javax.servlet.ServletException

java.io.IOException

doRequest

protected void doRequest(javax.servlet.http.HttpServletRequest request,
                         javax.servlet.http.HttpServletResponse response)
                  throws javax.servlet.ServletException,
                         java.io.IOException

Handles with both GET and POST requests

Parameters:

request - HttpServletRequest object containing client request

response - HttpServletResponse object for the response

Throws:

javax.servlet.ServletException

java.io.IOException

handleRequest

protected org.apache.velocity.Template handleRequest(javax.servlet.http.HttpServletRequest request,
                                                     javax.servlet.http.HttpServletResponse response,
                                                     org.apache.velocity.context.Context ctx)
                                              throws java.lang.Exception

Deprecated. This will be removed in VelocityTools 2.0.

This was a common extension point, but has been deprecated. It has no single replacement. Instead, you should override fillContext(org.apache.velocity.context.Context, javax.servlet.http.HttpServletRequest) to add custom things to the Context or override a getTemplate(javax.servlet.http.HttpServletRequest) method to change how Templates are retrieved

Parameters:

request - client request

response - client response

ctx - VelocityContext to fill

Returns:

Velocity Template object or null

Throws:

java.lang.Exception

createContext

protected org.apache.velocity.context.Context createContext(javax.servlet.http.HttpServletRequest request,
                                                            javax.servlet.http.HttpServletResponse response)

Creates and returns an initialized Velocity context.

A new context of class ChainedContext is created and initialized.

Parameters:

request - servlet request from client

response - servlet reponse to client

fillContext

protected void fillContext(org.apache.velocity.context.Context context,
                           javax.servlet.http.HttpServletRequest request)

This is an extension hook for users who subclass this servlet to make their own modifications to the Context. It is a partial replacement of the deprecated handleRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, org.apache.velocity.context.Context) method. This implementation does nothing.

setContentType

protected void setContentType(javax.servlet.http.HttpServletRequest request,
                              javax.servlet.http.HttpServletResponse response)

Sets the content type of the response. This is available to be overriden by a derived class.

The default implementation is :

    response.setContentType(defaultContentType);
 

where defaultContentType is set to the value of the default.contentType property, or "text/html" if that is not set.

Parameters:

request - servlet request from client

response - servlet reponse to client

getTemplate

protected org.apache.velocity.Template getTemplate(javax.servlet.http.HttpServletRequest request)
                                            throws org.apache.velocity.exception.ResourceNotFoundException,
                                                   org.apache.velocity.exception.ParseErrorException,
                                                   java.lang.Exception

Gets the requested template.

Parameters:

request - client request

Returns:

Velocity Template object or null

Throws:

org.apache.velocity.exception.ResourceNotFoundException

org.apache.velocity.exception.ParseErrorException

java.lang.Exception

getTemplate

protected org.apache.velocity.Template getTemplate(javax.servlet.http.HttpServletRequest request,
                                                   javax.servlet.http.HttpServletResponse response)
                                            throws org.apache.velocity.exception.ResourceNotFoundException,
                                                   org.apache.velocity.exception.ParseErrorException,
                                                   java.lang.Exception

Gets the requested template.

Parameters:

request - client request

response - client response (whose character encoding we'll use)

Returns:

Velocity Template object or null

Throws:

org.apache.velocity.exception.ResourceNotFoundException

org.apache.velocity.exception.ParseErrorException

java.lang.Exception

getTemplate

public org.apache.velocity.Template getTemplate(java.lang.String name)
                                         throws org.apache.velocity.exception.ResourceNotFoundException,
                                                org.apache.velocity.exception.ParseErrorException,
                                                java.lang.Exception

Retrieves the requested template.

Parameters:

name - The file name of the template to retrieve relative to the template root.

Returns:

The requested template.

Throws:

org.apache.velocity.exception.ResourceNotFoundException - if template not found from any available source.

org.apache.velocity.exception.ParseErrorException - if template cannot be parsed due to syntax (or other) error.

java.lang.Exception - if an error occurs in template initialization

getTemplate

public org.apache.velocity.Template getTemplate(java.lang.String name,
                                                java.lang.String encoding)
                                         throws org.apache.velocity.exception.ResourceNotFoundException,
                                                org.apache.velocity.exception.ParseErrorException,
                                                java.lang.Exception

Retrieves the requested template with the specified character encoding.

Parameters:

name - The file name of the template to retrieve relative to the template root.

encoding - the character encoding of the template

Returns:

The requested template.

Throws:

org.apache.velocity.exception.ResourceNotFoundException - if template not found from any available source.

org.apache.velocity.exception.ParseErrorException - if template cannot be parsed due to syntax (or other) error.

java.lang.Exception - if an error occurs in template initialization

mergeTemplate

protected void mergeTemplate(org.apache.velocity.Template template,
                             org.apache.velocity.context.Context context,
                             javax.servlet.http.HttpServletResponse response)
                      throws org.apache.velocity.exception.ResourceNotFoundException,
                             org.apache.velocity.exception.ParseErrorException,
                             org.apache.velocity.exception.MethodInvocationException,
                             java.io.IOException,
                             java.io.UnsupportedEncodingException,
                             java.lang.Exception

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 :)

Parameters:

template - template object returned by the handleRequest() method

context - Context created by the createContext(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)

response - servlet reponse (used to get a Writer)

Throws:

org.apache.velocity.exception.ResourceNotFoundException

org.apache.velocity.exception.ParseErrorException

org.apache.velocity.exception.MethodInvocationException

java.io.IOException

java.io.UnsupportedEncodingException

java.lang.Exception

performMerge

protected void performMerge(org.apache.velocity.Template template,
                            org.apache.velocity.context.Context context,
                            java.io.Writer writer)
                     throws org.apache.velocity.exception.ResourceNotFoundException,
                            org.apache.velocity.exception.ParseErrorException,
                            org.apache.velocity.exception.MethodInvocationException,
                            java.lang.Exception

This is here so developers may override it and gain access to the Writer which the template will be merged into. See VELTOOLS-7 for discussion of this.

Parameters:

template - template object returned by the handleRequest() method

context - Context created by the createContext(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)

writer - a VelocityWriter that the template is merged into

Throws:

org.apache.velocity.exception.ResourceNotFoundException

org.apache.velocity.exception.ParseErrorException

org.apache.velocity.exception.MethodInvocationException

java.lang.Exception

error

protected void error(javax.servlet.http.HttpServletRequest request,
                     javax.servlet.http.HttpServletResponse response,
                     java.lang.Exception e)
              throws javax.servlet.ServletException

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.

Parameters:

request - original HttpServletRequest from servlet container.

response - HttpServletResponse object from servlet container.

e - Exception that was thrown by some other part of process.

Throws:

javax.servlet.ServletException

getResponseWriter

protected java.io.Writer getResponseWriter(javax.servlet.http.HttpServletResponse response)
                                    throws java.io.UnsupportedEncodingException,
                                           java.io.IOException

Procure a Writer with correct encoding which can be used even if HttpServletResponse's getOutputStream() method has already been called.

This is a transitional method which will be removed in a future version of Velocity. It is not recommended that you override this method.

Parameters:

response - The response.

Returns:

A Writer, possibly created using the getOutputStream().

Throws:

java.io.UnsupportedEncodingException

java.io.IOException

requestCleanup

protected void requestCleanup(javax.servlet.http.HttpServletRequest request,
                              javax.servlet.http.HttpServletResponse response,
                              org.apache.velocity.context.Context context)

Cleanup routine called at the end of the request processing sequence allows a derived class to do resource cleanup or other end of process cycle tasks. This default implementation does nothing.

Parameters:

request - servlet request from client

response - servlet reponse

context - Context created by the createContext(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)