org.springframework.web.servlet.view.velocity
Class VelocityView

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

All Implemented Interfaces:

BeanNameAware, InitializingBean, ApplicationContextAware, ServletContextAware, View

Direct Known Subclasses:

VelocityToolboxView

public class VelocityView
extends AbstractTemplateView

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).

Author:

Rod Johnson, Juergen Hoeller, Dave Syer

See Also:

VelocityConfig, VelocityConfigurer, AbstractUrlBasedView.setUrl(java.lang.String), AbstractTemplateView.setExposeSpringMacroHelpers(boolean), setEncoding(java.lang.String), setVelocityEngine(org.apache.velocity.app.VelocityEngine), VelocityConfig, VelocityConfigurer

Field Summary

Fields inherited from class org.springframework.web.servlet.view.AbstractTemplateView

SPRING_MACRO_REQUEST_CONTEXT_ATTRIBUTE

Fields inherited from class org.springframework.web.servlet.view.AbstractView

DEFAULT_CONTENT_TYPE

Fields inherited from class org.springframework.context.support.ApplicationObjectSupport

logger

Fields inherited from interface org.springframework.web.servlet.View

RESPONSE_STATUS_ATTRIBUTE

Constructor Summary

VelocityView()

Method Summary

protected VelocityEngine	autodetectVelocityEngine() Autodetect a VelocityEngine via the ApplicationContext.
boolean	checkResource(Locale locale) Check that the Velocity template used for this view exists and is valid.
protected Context	createVelocityContext(Map<String,Object> model) Create a Velocity Context instance for the given model, to be passed to the template for merging.
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.
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.
protected void	exposeHelpers(Context velocityContext, HttpServletRequest request) Expose helpers unique to each rendering operation.
protected void	exposeHelpers(Context velocityContext, HttpServletRequest request, HttpServletResponse response) Expose helpers unique to each rendering operation.
protected void	exposeHelpers(Map<String,Object> model, HttpServletRequest request) Expose helpers unique to each rendering operation.
protected void	exposeToolAttributes(Context velocityContext, HttpServletRequest request) Expose the tool attributes, according to corresponding bean property settings.
protected String	getEncoding() Return the encoding for the Velocity template.
protected Template	getTemplate() Retrieve the Velocity template to be rendered by this view.
protected Template	getTemplate(String name) Retrieve the Velocity template specified by the given name, using the encoding specified by the "encoding" bean property.
protected VelocityEngine	getVelocityEngine() Return the VelocityEngine used by this view.
protected void	initApplicationContext() Invoked on startup.
protected void	initTool(Object tool, Context velocityContext) Initialize the given tool instance.
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.
protected void	renderMergedTemplateModel(Map<String,Object> model, HttpServletRequest request, HttpServletResponse response) Process the model map by merging it with the Velocity template.
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.

Methods inherited from class org.springframework.web.servlet.view.AbstractTemplateView

applyContentType, renderMergedOutputModel, setAllowRequestOverride, setAllowSessionOverride, setExposeRequestAttributes, setExposeSessionAttributes, setExposeSpringMacroHelpers

Methods inherited from class org.springframework.web.servlet.view.AbstractUrlBasedView

afterPropertiesSet, getUrl, isUrlRequired, setUrl, toString

Methods inherited from class org.springframework.web.servlet.view.AbstractView

addStaticAttribute, createRequestContext, createTemporaryOutputStream, exposeModelAsRequestAttributes, generatesDownloadContent, getAttributesMap, getBeanName, getContentType, getRequestContextAttribute, getStaticAttributes, prepareResponse, render, setAttributes, setAttributesCSV, setAttributesMap, setBeanName, setContentType, setRequestContextAttribute, writeToResponse

Methods inherited from class org.springframework.web.context.support.WebApplicationObjectSupport

getServletContext, getTempDir, getWebApplicationContext, initApplicationContext, initServletContext, isContextRequired, setServletContext

Methods inherited from class org.springframework.context.support.ApplicationObjectSupport

getApplicationContext, getMessageSourceAccessor, requiredContextClass, setApplicationContext

Methods inherited from class java.lang.Object

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

Constructor Detail

VelocityView

public VelocityView()

Method Detail

setToolAttributes

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:

MathTool, VelocityToolboxView, createVelocityContext(java.util.Map, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), initTool(java.lang.Object, org.apache.velocity.context.Context), setDateToolAttribute(java.lang.String), setNumberToolAttribute(java.lang.String)

setDateToolAttribute

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:

DateTool, RequestContextUtils.getLocale(javax.servlet.http.HttpServletRequest), LocaleResolver

setNumberToolAttribute

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:

NumberTool, RequestContextUtils.getLocale(javax.servlet.http.HttpServletRequest), LocaleResolver

setEncoding

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.

getEncoding

protected String getEncoding()

Return the encoding for the Velocity template.

setCacheTemplate

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.

isCacheTemplate

protected boolean isCacheTemplate()

Return whether the Velocity template should be cached.

setVelocityEngine

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:

VelocityConfig

getVelocityEngine

protected VelocityEngine getVelocityEngine()

Return the VelocityEngine used by this view.

initApplicationContext

protected void initApplicationContext()
                               throws BeansException

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

Overrides:

initApplicationContext in class ApplicationObjectSupport

Throws:

ApplicationContextException - in case of initialization errors

BeansException - if thrown by ApplicationContext methods

See Also:

ApplicationObjectSupport.setApplicationContext(org.springframework.context.ApplicationContext)

autodetectVelocityEngine

protected VelocityEngine autodetectVelocityEngine()
                                           throws BeansException

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:

ApplicationObjectSupport.getApplicationContext(), setVelocityEngine(org.apache.velocity.app.VelocityEngine)

checkResource

public boolean checkResource(Locale locale)
                      throws Exception

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.

Overrides:

checkResource in class AbstractUrlBasedView

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 - if the resource exists but is invalid (e.g. could not be parsed)

renderMergedTemplateModel

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

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.

Specified by:

renderMergedTemplateModel in class AbstractTemplateView

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 - if rendering failed

exposeHelpers

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

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:

renderMergedTemplateModel(java.util.Map, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)

createVelocityContext

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

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:

createVelocityContext(Map), initTool(java.lang.Object, org.apache.velocity.context.Context), ChainedContext, VelocityToolboxView

createVelocityContext

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

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:

VelocityContext

exposeHelpers

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

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)

exposeHelpers

protected void exposeHelpers(Context velocityContext,
                             HttpServletRequest request)
                      throws Exception

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:

exposeHelpers(Map, HttpServletRequest)

exposeToolAttributes

protected void exposeToolAttributes(Context velocityContext,
                                    HttpServletRequest request)
                             throws Exception

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:

setDateToolAttribute(java.lang.String), setNumberToolAttribute(java.lang.String), exposeHelpers(Map, HttpServletRequest), exposeHelpers(org.apache.velocity.context.Context, HttpServletRequest, HttpServletResponse)

initTool

protected void initTool(Object tool,
                        Context velocityContext)
                 throws Exception

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:

createVelocityContext(java.util.Map, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse), ViewContext, ChainedContext, VelocityToolboxView

doRender

protected void doRender(Context context,
                        HttpServletResponse response)
                 throws Exception

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:

AbstractUrlBasedView.setUrl(java.lang.String), getTemplate(), mergeTemplate(org.apache.velocity.Template, org.apache.velocity.context.Context, javax.servlet.http.HttpServletResponse)

getTemplate

protected Template getTemplate()
                        throws Exception

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:

AbstractUrlBasedView.setUrl(java.lang.String), setCacheTemplate(boolean), getTemplate(String)

getTemplate

protected Template getTemplate(String name)
                        throws Exception

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:

VelocityEngine.getTemplate(java.lang.String)

mergeTemplate

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

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:

Template.merge(org.apache.velocity.context.Context, java.io.Writer)