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
    --- | ---
    `static String` | `METHOD_GET` HTTP method "GET"
    `static String` | `METHOD_HEAD` HTTP method "HEAD"
    `static String` | `METHOD_POST` HTTP method "POST"

    - ### 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(String... supportedMethods)` Create a new WebContentGenerator.

  - ### Method Summary

    Methods
    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.
    `String[]` | `getSupportedMethods()` Return the HTTP methods that this content generator supports.
    `boolean` | `isAlwaysMustRevalidate()` Return whether 'must-revaliate' 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(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 String METHOD_GET

      HTTP method "GET"
      See Also:
        Constant Field Values

    - #### METHOD_HEAD

          public static final String METHOD_HEAD

      HTTP method "HEAD"
      See Also:
        Constant Field Values

    - #### METHOD_POST

          public static final String METHOD_POST

      HTTP method "POST"
      See Also:
        Constant Field Values

  - ### 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(String... supportedMethods)

      Create a new WebContentGenerator.
      Parameters:
        `supportedMethods` - the supported HTTP methods for this content generator

  - ### Method Detail

    - #### setSupportedMethods

          public final void setSupportedMethods(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 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-revaliate' 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)