org.springframework.web.servlet.support

Class WebContentGenerator

java.lang.Object

org.springframework.context.support.ApplicationObjectSupport

org.springframework.web.context.support.WebApplicationObjectSupport

org.springframework.web.servlet.support.WebContentGenerator

All Implemented Interfaces:

Aware, ApplicationContextAware, ServletContextAware

Direct Known Subclasses:

AbstractController, AbstractHandlerMethodAdapter, AnnotationMethodHandlerAdapter, ResourceHttpRequestHandler, WebContentInterceptor

public abstract class WebContentGenerator
extends WebApplicationObjectSupport

Convenient superclass for any kind of web content generator, like AbstractController and WebContentInterceptor. Can also be used for custom handlers that have their own HandlerAdapter.

Supports HTTP cache control options. The usage of corresponding HTTP headers can be controlled via the "useExpiresHeader", "useCacheControlHeader" and "useCacheControlNoStore" properties.

Author:

Rod Johnson, Juergen Hoeller

See Also:

setCacheSeconds(int), setRequireSession(boolean)

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	alwaysMustRevalidate
private int	cacheSeconds
private static java.lang.String	HEADER_CACHE_CONTROL
private static java.lang.String	HEADER_EXPIRES
private static java.lang.String	HEADER_PRAGMA
static java.lang.String	METHOD_GET HTTP method "GET"
static java.lang.String	METHOD_HEAD HTTP method "HEAD"
static java.lang.String	METHOD_POST HTTP method "POST"
private boolean	requireSession
private java.util.Set<java.lang.String>	supportedMethods Set of supported HTTP methods
private boolean	useCacheControlHeader Use HTTP 1.1 cache-control header?
private boolean	useCacheControlNoStore Use HTTP 1.1 cache-control header value "no-store"?
private boolean	useExpiresHeader Use HTTP 1.0 expires header?

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

logger

Constructor Summary

Constructors

Constructor and Description
WebContentGenerator() Create a new WebContentGenerator which supports HTTP methods GET, HEAD and POST by default.
WebContentGenerator(boolean restrictDefaultSupportedMethods) Create a new WebContentGenerator.
WebContentGenerator(java.lang.String... supportedMethods) Create a new WebContentGenerator.

Method Summary

Modifier and Type	Method and Description
protected void	applyCacheSeconds(HttpServletResponse response, int seconds) Apply the given cache seconds and generate corresponding HTTP headers, i.e.
protected void	applyCacheSeconds(HttpServletResponse response, int seconds, boolean mustRevalidate) Apply the given cache seconds and generate respective HTTP headers.
protected void	cacheForSeconds(HttpServletResponse response, int seconds) Set HTTP headers to allow caching for the given number of seconds.
protected void	cacheForSeconds(HttpServletResponse response, int seconds, boolean mustRevalidate) Set HTTP headers to allow caching for the given number of seconds.
protected void	checkAndPrepare(HttpServletRequest request, HttpServletResponse response, boolean lastModified) Check and prepare the given request and response according to the settings of this generator.
protected void	checkAndPrepare(HttpServletRequest request, HttpServletResponse response, int cacheSeconds, boolean lastModified) Check and prepare the given request and response according to the settings of this generator.
int	getCacheSeconds() Return the number of seconds that content is cached.
java.lang.String[]	getSupportedMethods() Return the HTTP methods that this content generator supports.
boolean	isAlwaysMustRevalidate() Return whether 'must-revalidate' is added to every Cache-Control header.
boolean	isRequireSession() Return whether a session is required to handle requests.
boolean	isUseCacheControlHeader() Return whether the HTTP 1.1 cache-control header is used.
boolean	isUseCacheControlNoStore() Return whether the HTTP 1.1 cache-control header value "no-store" is used.
boolean	isUseExpiresHeader() Return whether the HTTP 1.0 expires header is used.
protected void	preventCaching(HttpServletResponse response) Prevent the response from being cached.
void	setAlwaysMustRevalidate(boolean mustRevalidate) An option to add 'must-revalidate' to every Cache-Control header.
void	setCacheSeconds(int seconds) Cache content for the given number of seconds.
void	setRequireSession(boolean requireSession) Set whether a session should be required to handle requests.
void	setSupportedMethods(java.lang.String[] methods) Set the HTTP methods that this content generator should support.
void	setUseCacheControlHeader(boolean useCacheControlHeader) Set whether to use the HTTP 1.1 cache-control header.
void	setUseCacheControlNoStore(boolean useCacheControlNoStore) Set whether to use the HTTP 1.1 cache-control header value "no-store" when preventing caching.
void	setUseExpiresHeader(boolean useExpiresHeader) Set whether to use the HTTP 1.0 expires header.

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, initApplicationContext, requiredContextClass, setApplicationContext

Methods inherited from class java.lang.Object

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

Field Detail

METHOD_GET

public static final java.lang.String METHOD_GET

HTTP method "GET"

See Also:

Constant Field Values

METHOD_HEAD

public static final java.lang.String METHOD_HEAD

HTTP method "HEAD"

See Also:

Constant Field Values

METHOD_POST

public static final java.lang.String METHOD_POST

HTTP method "POST"

See Also:

Constant Field Values

HEADER_PRAGMA

private static final java.lang.String HEADER_PRAGMA

See Also:

Constant Field Values

HEADER_EXPIRES

private static final java.lang.String HEADER_EXPIRES

See Also:

Constant Field Values

HEADER_CACHE_CONTROL

private static final java.lang.String HEADER_CACHE_CONTROL

See Also:

Constant Field Values

supportedMethods

private java.util.Set<java.lang.String> supportedMethods

Set of supported HTTP methods

requireSession

private boolean requireSession

useExpiresHeader

private boolean useExpiresHeader

Use HTTP 1.0 expires header?

useCacheControlHeader

private boolean useCacheControlHeader

Use HTTP 1.1 cache-control header?

useCacheControlNoStore

private boolean useCacheControlNoStore

Use HTTP 1.1 cache-control header value "no-store"?

cacheSeconds

private int cacheSeconds

alwaysMustRevalidate

private boolean alwaysMustRevalidate

Constructor Detail

WebContentGenerator

public WebContentGenerator()

Create a new WebContentGenerator which supports HTTP methods GET, HEAD and POST by default.

WebContentGenerator

public WebContentGenerator(boolean restrictDefaultSupportedMethods)

Create a new WebContentGenerator.

Parameters:

restrictDefaultSupportedMethods - true if this generator should support HTTP methods GET, HEAD and POST by default, or false if it should be unrestricted

WebContentGenerator

public WebContentGenerator(java.lang.String... supportedMethods)

Create a new WebContentGenerator.

Parameters:

supportedMethods - the supported HTTP methods for this content generator

Method Detail

setSupportedMethods

public final void setSupportedMethods(java.lang.String[] methods)

Set the HTTP methods that this content generator should support.

Default is GET, HEAD and POST for simple form controller types; unrestricted for general controllers and interceptors.

getSupportedMethods

public final java.lang.String[] getSupportedMethods()

Return the HTTP methods that this content generator supports.

setRequireSession

public final void setRequireSession(boolean requireSession)

Set whether a session should be required to handle requests.

isRequireSession

public final boolean isRequireSession()

Return whether a session is required to handle requests.

setUseExpiresHeader

public final void setUseExpiresHeader(boolean useExpiresHeader)

Set whether to use the HTTP 1.0 expires header. Default is "true".

Note: Cache headers will only get applied if caching is enabled (or explicitly prevented) for the current request.

isUseExpiresHeader

public final boolean isUseExpiresHeader()

Return whether the HTTP 1.0 expires header is used.

setUseCacheControlHeader

public final void setUseCacheControlHeader(boolean useCacheControlHeader)

Set whether to use the HTTP 1.1 cache-control header. Default is "true".

Note: Cache headers will only get applied if caching is enabled (or explicitly prevented) for the current request.

isUseCacheControlHeader

public final boolean isUseCacheControlHeader()

Return whether the HTTP 1.1 cache-control header is used.

setUseCacheControlNoStore

public final void setUseCacheControlNoStore(boolean useCacheControlNoStore)

Set whether to use the HTTP 1.1 cache-control header value "no-store" when preventing caching. Default is "true".

isUseCacheControlNoStore

public final boolean isUseCacheControlNoStore()

Return whether the HTTP 1.1 cache-control header value "no-store" is used.

setAlwaysMustRevalidate

public void setAlwaysMustRevalidate(boolean mustRevalidate)

An option to add 'must-revalidate' to every Cache-Control header. This may be useful with annotated controller methods, which can programmatically do a lastModified calculation as described in WebRequest.checkNotModified(long). Default is "false", effectively relying on whether the handler implements LastModified or not.

isAlwaysMustRevalidate

public boolean isAlwaysMustRevalidate()

Return whether 'must-revalidate' is added to every Cache-Control header.

setCacheSeconds

public final void setCacheSeconds(int seconds)

Cache content for the given number of seconds. Default is -1, indicating no generation of cache-related headers.

Only if this is set to 0 (no cache) or a positive value (cache for this many seconds) will this class generate cache headers.

The headers can be overwritten by subclasses, before content is generated.

getCacheSeconds

public final int getCacheSeconds()

Return the number of seconds that content is cached.

checkAndPrepare

protected final void checkAndPrepare(HttpServletRequest request,
                                     HttpServletResponse response,
                                     boolean lastModified)
                              throws ServletException

Check and prepare the given request and response according to the settings of this generator. Checks for supported methods and a required session, and applies the number of cache seconds specified for this generator.

Parameters:

request - current HTTP request

response - current HTTP response

lastModified - if the mapped handler provides Last-Modified support

Throws:

ServletException - if the request cannot be handled because a check failed

checkAndPrepare

protected final void checkAndPrepare(HttpServletRequest request,
                                     HttpServletResponse response,
                                     int cacheSeconds,
                                     boolean lastModified)
                              throws ServletException

Check and prepare the given request and response according to the settings of this generator. Checks for supported methods and a required session, and applies the given number of cache seconds.

Parameters:

request - current HTTP request

response - current HTTP response

cacheSeconds - positive number of seconds into the future that the response should be cacheable for, 0 to prevent caching

lastModified - if the mapped handler provides Last-Modified support

Throws:

ServletException - if the request cannot be handled because a check failed

preventCaching

protected final void preventCaching(HttpServletResponse response)

Prevent the response from being cached. See http://www.mnot.net/cache_docs.

cacheForSeconds

protected final void cacheForSeconds(HttpServletResponse response,
                                     int seconds)

Set HTTP headers to allow caching for the given number of seconds. Does not tell the browser to revalidate the resource.

Parameters:

response - current HTTP response

seconds - number of seconds into the future that the response should be cacheable for

See Also:

#cacheForSeconds(javax.servlet.http.HttpServletResponse, int, boolean)

cacheForSeconds

protected final void cacheForSeconds(HttpServletResponse response,
                                     int seconds,
                                     boolean mustRevalidate)

Set HTTP headers to allow caching for the given number of seconds. Tells the browser to revalidate the resource if mustRevalidate is true.

Parameters:

response - the current HTTP response

seconds - number of seconds into the future that the response should be cacheable for

mustRevalidate - whether the client should revalidate the resource (typically only necessary for controllers with last-modified support)

applyCacheSeconds

protected final void applyCacheSeconds(HttpServletResponse response,
                                       int seconds)

Apply the given cache seconds and generate corresponding HTTP headers, i.e. allow caching for the given number of seconds in case of a positive value, prevent caching if given a 0 value, do nothing else. Does not tell the browser to revalidate the resource.

Parameters:

response - current HTTP response

seconds - positive number of seconds into the future that the response should be cacheable for, 0 to prevent caching

See Also:

#cacheForSeconds(javax.servlet.http.HttpServletResponse, int, boolean)

applyCacheSeconds

protected final void applyCacheSeconds(HttpServletResponse response,
                                       int seconds,
                                       boolean mustRevalidate)

Apply the given cache seconds and generate respective HTTP headers.

That is, allow caching for the given number of seconds in the case of a positive value, prevent caching if given a 0 value, else do nothing (i.e. leave caching to the client).

Parameters:

response - the current HTTP response

seconds - the (positive) number of seconds into the future that the response should be cacheable for; 0 to prevent caching; and a negative value to leave caching to the client.

mustRevalidate - whether the client should revalidate the resource (typically only necessary for controllers with last-modified support)