public class

VelocityView

extends AbstractTemplateView
java.lang.Object
   ↳ org.springframework.context.support.ApplicationObjectSupport
     ↳ org.springframework.web.context.support.WebApplicationObjectSupport
       ↳ org.springframework.web.servlet.view.AbstractView
         ↳ org.springframework.web.servlet.view.AbstractUrlBasedView
           ↳ org.springframework.web.servlet.view.AbstractTemplateView
             ↳ org.springframework.web.servlet.view.velocity.VelocityView
Known Direct Subclasses
Known Indirect Subclasses

Class Overview

View using the Velocity template engine.

Exposes the following JavaBean properties:

  • url: the location of the Velocity template to be wrapped, relative to the Velocity resource loader path (see VelocityConfigurer).
  • encoding (optional, default is determined by Velocity configuration): the encoding of the Velocity template file
  • velocityFormatterAttribute (optional, default=null): the name of the VelocityFormatter helper object to expose in the Velocity context of this view, or null if not needed. VelocityFormatter is part of standard Velocity.
  • dateToolAttribute (optional, default=null): the name of the DateTool helper object to expose in the Velocity context of this view, or null if not needed. DateTool is part of Velocity Tools.
  • numberToolAttribute (optional, default=null): the name of the NumberTool helper object to expose in the Velocity context of this view, or null if not needed. NumberTool is part of Velocity Tools.
  • cacheTemplate (optional, default=false): whether or not the Velocity template should be cached. It should normally be true in production, but setting this to false enables us to modify Velocity templates without restarting the application (similar to JSPs). Note that this is a minor optimization only, as Velocity itself caches templates in a modification-aware fashion.

Depends on a VelocityConfig object such as VelocityConfigurer being accessible in the current web application context, with any bean name. Alternatively, you can set the VelocityEngine object as bean property.

Note: Spring 3.0's VelocityView requires Velocity 1.4 or higher, and optionally Velocity Tools 1.1 or higher (depending on the use of DateTool and/or NumberTool).

See Also

Summary

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Inherited Constants
From class org.springframework.web.servlet.view.AbstractTemplateView
From class org.springframework.web.servlet.view.AbstractView
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Inherited Fields
From class org.springframework.context.support.ApplicationObjectSupport
From interface org.springframework.web.servlet.View
Public Constructors
VelocityView()
Public Methods
boolean checkResource(Locale locale)
Check that the Velocity template used for this view exists and is valid.
void setCacheTemplate(boolean cacheTemplate)
Set whether the Velocity template should be cached.
void setDateToolAttribute(String dateToolAttribute)
Set the name of the DateTool helper object to expose in the Velocity context of this view, or null if not needed.
void setEncoding(String encoding)
Set the encoding of the Velocity template file.
void setNumberToolAttribute(String numberToolAttribute)
Set the name of the NumberTool helper object to expose in the Velocity context of this view, or null if not needed.
void setToolAttributes(Map<String, Class> toolAttributes)
Set tool attributes to expose to the view, as attribute name / class name pairs.
void setVelocityEngine(VelocityEngine velocityEngine)
Set the VelocityEngine to be used by this view.
Protected Methods
VelocityEngine autodetectVelocityEngine()
Autodetect a VelocityEngine via the ApplicationContext.
Context createVelocityContext(Map<String, Object> model)
Create a Velocity Context instance for the given model, to be passed to the template for merging.
Context createVelocityContext(Map<String, Object> model, HttpServletRequest request, HttpServletResponse response)
Create a Velocity Context instance for the given model, to be passed to the template for merging.
void doRender(Context context, HttpServletResponse response)
Render the Velocity view to the given response, using the given Velocity context which contains the complete template model to use.
void exposeHelpers(Context velocityContext, HttpServletRequest request)
Expose helpers unique to each rendering operation.
void exposeHelpers(Map<String, Object> model, HttpServletRequest request)
Expose helpers unique to each rendering operation.
void exposeHelpers(Context velocityContext, HttpServletRequest request, HttpServletResponse response)
Expose helpers unique to each rendering operation.
void exposeToolAttributes(Context velocityContext, HttpServletRequest request)
Expose the tool attributes, according to corresponding bean property settings.
String getEncoding()
Return the encoding for the Velocity template.
Template getTemplate(String name)
Retrieve the Velocity template specified by the given name, using the encoding specified by the "encoding" bean property.
Template getTemplate()
Retrieve the Velocity template to be rendered by this view.
VelocityEngine getVelocityEngine()
Return the VelocityEngine used by this view.
void initApplicationContext()
Invoked on startup.
void initTool(Object tool, Context velocityContext)
Initialize the given tool instance.
boolean isCacheTemplate()
Return whether the Velocity template should be cached.
void mergeTemplate(Template template, Context context, HttpServletResponse response)
Merge the template with the context.
void renderMergedTemplateModel(Map<String, Object> model, HttpServletRequest request, HttpServletResponse response)
Process the model map by merging it with the Velocity template.
[Expand]
Inherited Methods
From class org.springframework.web.servlet.view.AbstractTemplateView
From class org.springframework.web.servlet.view.AbstractUrlBasedView
From class org.springframework.web.servlet.view.AbstractView
From class org.springframework.web.context.support.WebApplicationObjectSupport
From class org.springframework.context.support.ApplicationObjectSupport
From class java.lang.Object
From interface org.springframework.beans.factory.BeanNameAware
From interface org.springframework.beans.factory.InitializingBean
From interface org.springframework.context.ApplicationContextAware
From interface org.springframework.web.context.ServletContextAware
From interface org.springframework.web.servlet.View

Public Constructors

public VelocityView ()

Public Methods

public boolean checkResource (Locale locale)

Check that the Velocity template used for this view exists and is valid.

Can be overridden to customize the behavior, for example in case of multiple templates to be rendered into a single view.

Parameters
locale the desired Locale that we're looking for
Returns
  • true if the resource exists (or is assumed to exist); false if we know that it does not exist
Throws
Exception

public void setCacheTemplate (boolean cacheTemplate)

Set whether the Velocity template should be cached. Default is "false". It should normally be true in production, but setting this to false enables us to modify Velocity templates without restarting the application (similar to JSPs).

Note that this is a minor optimization only, as Velocity itself caches templates in a modification-aware fashion.

public void setDateToolAttribute (String dateToolAttribute)

Set the name of the DateTool helper object to expose in the Velocity context of this view, or null if not needed. The exposed DateTool will be aware of the current locale, as determined by Spring's LocaleResolver.

DateTool is part of the generic package of Velocity Tools 1.0. Spring uses a special locale-aware subclass of DateTool.

See Also

public void setEncoding (String encoding)

Set the encoding of the Velocity template file. Default is determined by the VelocityEngine: "ISO-8859-1" if not specified otherwise.

Specify the encoding in the VelocityEngine rather than per template if all your templates share a common encoding.

public void setNumberToolAttribute (String numberToolAttribute)

Set the name of the NumberTool helper object to expose in the Velocity context of this view, or null if not needed. The exposed NumberTool will be aware of the current locale, as determined by Spring's LocaleResolver.

NumberTool is part of the generic package of Velocity Tools 1.1. Spring uses a special locale-aware subclass of NumberTool.

See Also

public void setToolAttributes (Map<String, Class> toolAttributes)

Set tool attributes to expose to the view, as attribute name / class name pairs. An instance of the given class will be added to the Velocity context for each rendering operation, under the given attribute name.

For example, an instance of MathTool, which is part of the generic package of Velocity Tools, can be bound under the attribute name "math", specifying the fully qualified class name "org.apache.velocity.tools.generic.MathTool" as value.

Note that VelocityView can only create simple generic tools or values, that is, classes with a public default constructor and no further initialization needs. This class does not do any further checks, to not introduce a required dependency on a specific tools package.

For tools that are part of the view package of Velocity Tools, a special Velocity context and a special init callback are needed. Use VelocityToolboxView in such a case, or override createVelocityContext and initTool accordingly.

For a simple VelocityFormatter instance or special locale-aware instances of DateTool/NumberTool, which are part of the generic package of Velocity Tools, specify the "velocityFormatterAttribute", "dateToolAttribute" or "numberToolAttribute" properties, respectively.

Parameters
toolAttributes attribute names as keys, and tool class names as values
See Also

public void setVelocityEngine (VelocityEngine velocityEngine)

Set the VelocityEngine to be used by this view.

If this is not set, the default lookup will occur: A single VelocityConfig is expected in the current web application context, with any bean name.

See Also

Protected Methods

protected VelocityEngine autodetectVelocityEngine ()

Autodetect a VelocityEngine via the ApplicationContext. Called if no explicit VelocityEngine has been specified.

Returns
  • the VelocityEngine to use for VelocityViews
Throws
BeansException if no VelocityEngine could be found
See Also

protected Context createVelocityContext (Map<String, Object> model)

Create a Velocity Context instance for the given model, to be passed to the template for merging.

Default implementation creates an instance of Velocity's VelocityContext implementation class.

Parameters
model the model Map, containing the model attributes to be exposed to the view
Returns
  • the Velocity Context
Throws
Exception if there's a fatal error while creating the context
See Also
  • org.apache.velocity.VelocityContext

protected Context createVelocityContext (Map<String, Object> model, HttpServletRequest request, HttpServletResponse response)

Create a Velocity Context instance for the given model, to be passed to the template for merging.

The default implementation delegates to createVelocityContext(Map). Can be overridden for a special context class, for example ChainedContext which is part of the view package of Velocity Tools. ChainedContext is needed for initialization of ViewTool instances.

Have a look at VelocityToolboxView, which pre-implements ChainedContext support. This is not part of the standard VelocityView class in order to avoid a required dependency on the view package of Velocity Tools.

Parameters
model the model Map, containing the model attributes to be exposed to the view
request current HTTP request
response current HTTP response
Returns
  • the Velocity Context
Throws
Exception if there's a fatal error while creating the context
See Also

protected void doRender (Context context, HttpServletResponse response)

Render the Velocity view to the given response, using the given Velocity context which contains the complete template model to use.

The default implementation renders the template specified by the "url" bean property, retrieved via getTemplate. It delegates to the mergeTemplate method to merge the template instance with the given Velocity context.

Can be overridden to customize the behavior, for example to render multiple templates into a single view.

Parameters
context the Velocity context to use for rendering
response servlet response (use this to get the OutputStream or Writer)
Throws
Exception if thrown by Velocity
See Also

protected void exposeHelpers (Context velocityContext, HttpServletRequest request)

Expose helpers unique to each rendering operation. This is necessary so that different rendering operations can't overwrite each other's formats etc.

Default implementation is empty. This method can be overridden to add custom helpers to the Velocity context.

Parameters
velocityContext Velocity context that will be passed to the template
request current HTTP request
Throws
Exception if there's a fatal error while we're adding model attributes
See Also

protected void exposeHelpers (Map<String, Object> model, HttpServletRequest request)

Expose helpers unique to each rendering operation. This is necessary so that different rendering operations can't overwrite each other's formats etc.

Called by renderMergedTemplateModel. The default implementation is empty. This method can be overridden to add custom helpers to the model.

Parameters
model the model that will be passed to the template for merging
request current HTTP request
Throws
Exception if there's a fatal error while we're adding model attributes
See Also

protected void exposeHelpers (Context velocityContext, HttpServletRequest request, HttpServletResponse response)

Expose helpers unique to each rendering operation. This is necessary so that different rendering operations can't overwrite each other's formats etc.

Called by renderMergedTemplateModel. Default implementation delegates to exposeHelpers(velocityContext, request). This method can be overridden to add special tools to the context, needing the servlet response to initialize (see Velocity Tools, for example LinkTool and ViewTool/ChainedContext).

Parameters
velocityContext Velocity context that will be passed to the template
request current HTTP request
response current HTTP response
Throws
Exception if there's a fatal error while we're adding model attributes
See Also
  • #exposeHelpers(org.apache.velocity.context.Context, HttpServletRequest)

protected void exposeToolAttributes (Context velocityContext, HttpServletRequest request)

Expose the tool attributes, according to corresponding bean property settings.

Do not override this method unless for further tools driven by bean properties. Override one of the exposeHelpers methods to add custom helpers.

Parameters
velocityContext Velocity context that will be passed to the template
request current HTTP request
Throws
Exception if there's a fatal error while we're adding model attributes
See Also

protected String getEncoding ()

Return the encoding for the Velocity template.

protected Template getTemplate (String name)

Retrieve the Velocity template specified by the given name, using the encoding specified by the "encoding" bean property.

Can be called by subclasses to retrieve a specific template, for example to render multiple templates into a single view.

Parameters
name the file name of the desired template
Returns
  • the Velocity template
Throws
Exception if thrown by Velocity
See Also
  • org.apache.velocity.app.VelocityEngine#getTemplate

protected Template getTemplate ()

Retrieve the Velocity template to be rendered by this view.

By default, the template specified by the "url" bean property will be retrieved: either returning a cached template instance or loading a fresh instance (according to the "cacheTemplate" bean property)

Returns
  • the Velocity template to render
Throws
Exception if thrown by Velocity
See Also

protected VelocityEngine getVelocityEngine ()

Return the VelocityEngine used by this view.

protected void initApplicationContext ()

Invoked on startup. Looks for a single VelocityConfig bean to find the relevant VelocityEngine for this factory.

Throws
BeansException

protected void initTool (Object tool, Context velocityContext)

Initialize the given tool instance. The default implementation is empty.

Can be overridden to check for special callback interfaces, for example the ViewContext interface which is part of the view package of Velocity Tools. In the particular case of ViewContext, you'll usually also need a special Velocity context, like ChainedContext which is part of Velocity Tools too.

Have a look at VelocityToolboxView, which pre-implements such a ViewTool check. This is not part of the standard VelocityView class in order to avoid a required dependency on the view package of Velocity Tools.

Parameters
tool the tool instance to initialize
velocityContext the Velocity context
Throws
Exception if initializion of the tool failed
See Also

protected boolean isCacheTemplate ()

Return whether the Velocity template should be cached.

protected void mergeTemplate (Template template, Context context, HttpServletResponse response)

Merge the template with the context. Can be overridden to customize the behavior.

Parameters
template the template to merge
context the Velocity context to use for rendering
response servlet response (use this to get the OutputStream or Writer)
Throws
Exception if thrown by Velocity
See Also
  • org.apache.velocity.Template#merge

protected void renderMergedTemplateModel (Map<String, Object> model, HttpServletRequest request, HttpServletResponse response)

Process the model map by merging it with the Velocity template. Output is directed to the servlet response.

This method can be overridden if custom behavior is needed.

Parameters
model combined output Map, with request attributes and session attributes merged into it if required
request current HTTP request
response current HTTP response
Throws
Exception